Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A pen-tip pressure-based system for real-time handprinted character recognition Willey, Stephen Raymond 1979

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1979_A7 W54.pdf [ 12.71MB ]
Metadata
JSON: 831-1.0094674.json
JSON-LD: 831-1.0094674-ld.json
RDF/XML (Pretty): 831-1.0094674-rdf.xml
RDF/JSON: 831-1.0094674-rdf.json
Turtle: 831-1.0094674-turtle.txt
N-Triples: 831-1.0094674-rdf-ntriples.txt
Original Record: 831-1.0094674-source.json
Full Text
831-1.0094674-fulltext.txt
Citation
831-1.0094674.ris

Full Text

A P E N - T I P PRESSURE-BASED SYSTEM FOR R E A L - T I M E HANDPRINTED CHARACTER RECOGNITION by S t e p h e n Raymond W i l l e y B . E n g . , M c M a s t e r U n i v e r s i t y , 1976 A THESIS SUBMITTED I N P A R T I A L FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF A P P L I E D SCIENCE i n THE FACULTY OF GRADUATE STUDIES i n t h e Depa r tmen t o f E l e c t r i c a l E n g i n e e r i n g We a c c e p t t h i s t h e s i s as c o n f o r m i n g to t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF B R I T I S H COLUMBIA S e p t e m b e r , 1979 (cY S t e p h e n Raymond W i l l e y , 1979 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and st u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be gr a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f £l£crrticAt- SMSW£££JNG The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date I I OC^dllL tfytj ABSTRACT A n o n - l i n e h a n d p r i n t e d c h a r a c t e r r e c o g n i t i o n scheme was d e v e l o p e d , i m p l e m e n t e d , and t e s t e d . The s e l e c t e d s y m b o l c l a s s i n c l u d e d t h e n u m e r i c s s u b s e t o f t h e ANSI s t a n d a r d and n i n e s p e c i a l s y m b o l s d e f i n e d f o r a p r o p o s e d d e d i c a t e d g r a p h i c s e d i t o r s y s t e m . A p r i m a r y d e s i g n o b j e c t i v e was t o p r o v i d e an e n v i r o n m e n t t h a t w o u l d r e f l e c t t h e n o n - t e c h n i c a l u s e r ' s n a t u r a l t e n d e n c i e s . A X e b e c b a l l - p o i n t p e n w i t h a p r e s s u r e - s e n s i t i v e t i p m o n i t o r e d d r a g f o r c e s g e n e r a t e d i n t h e p l a n e o f t h e p a p e r . F o r c e i n f o r m a t i o n was a v a i l a b l e t o t h e p r o c e s s o r by p e r i o d i c a l l y s a m p l i n g a s t r a t e g i c a l l y p l a c e d s t r a i n - g a u g e a r r a y . D a t a were a n a l y z e d i n r e a l - t i m e t o p r o v i d e i m m e d i a t e i n f e r e n c e s c o n c e r n i n g s t r o k e m o t i o n . S i n c e p o s i t i o n a l i n f o r m a t i o n was n o t a v a i l a b l e no c o n s t r a i n t s w e r e p l a c e d on t h e w r i t i n g medium. The s y s t e m i s m i c r o p r o c e s s o r c o m p a t i b l e w i t h t o t a l s o f t w a r e c o m p r i s i n g l e s s t h a n 1500 1 6 - b i t w o r d s . I t i s a l s o v e r y CPU e f f i c i e n t o w i n g t o a m u l t i - l e v e l p r e - p r o c e s s i n g scheme t h a t s i g n i f i c a n t l y r e d u c e s t h e c o m p u t i n g b u r d e n . F e a t u r e e x t r a c t i o n i s s i m p l e and e f f e c t i v e . A h y s t e r e s i s scheme i s a p p l i e d a t a l l b o r d e r s o f t h e q u a n t i z a t i o n p l a n e t o h e l p e l i m i n a t e r e d u n d a n t d a t a . I n t h e f i n a l s t a g e i n p u t s y m b o l s a r e c l a s s i f i e d w i t h t h e a i d o f a m o d i f i e d t r e e s t r u c t u r e t h a t i s i n h e r e n t l y t o l e r a n t t o a l a r g e v a r i e t y o f l o c a l v a r i a t i o n s . The d i c t i o n a r y i s compac t and q u i c k l y t r a v e r s e d ; p r o v i s i o n f o r 19 s y m b o l s r e q u i r e s l e s s t h a n 250 w o r d s s i n c e o n l y a f r a c t i o n o f a l l a l l o w a b l e forms n e e d be e x p l i c i t e l y s p e c i f i e d . E x t e n s i v e t e s t i n g was c o n d u c t e d on t h e c o m p l e t e d r e c o g n i z e r . A s m a l l amount o f u s e r t r a i n i n g i s r e q u i r e d t o e n s u r e a d e q u a t e p e r f o r m a n c e . i i A t o t a l o f more t h a n 4000 c h a r a c t e r s o b t a i n e d f r o m 15 s u b j e c t s w e r e a n a l y z e d . E x p e r i e n c e d u s e r s a c h i e v e d a 96.3% a v e r a g e r e c o g n i t i o n r a t e and s c o r e s above 98% w e r e n o t uncommon. P e r f o r m a n c e i s i n d e p e n d e n t , o f c h a r a c t e r s i z e and p o s i t i o n and u s e r s a p p e a r t o r e t a i n s k i l l s a c q u i r e d d u r i n g t r a i n i n g . N o n -t e c h n i c a l and t e c h n i c a l u s e r s p e r f o r m e q u a l l y w e l l and a r e n o t d i s t r a c t e d b y the s m a l l amount o f h a r d w a r e i n v o l v e d . E f f o r t s w e r e d i r e c t e d t o d e t e r m i n e i f t h e s y s t e m c o u l d be d e d i c a t e d t o a p a r t i c u l a r u s e r . I n some c a s e s , i t was f o u n d t h a t d i c t i o n a r y r e c o n f i g u r a t i o n i m p r o v e d p e r f o r m a n c e m a r k e d l y . O p t i m a l s y s t e m p a r a m e t e r v a l u e s w e r e f a i r l y r o b u s t , o p t i m i z i n g f o r a s i n g l e s u b j e c t y i e l d e d good r e s u l t s f o r a l l s u b j e c t s . E x c e p t i o n a l w r i t e r s , h o w e v e r , m i g h t b e n e f i t f rom some p a r a m e t e r f i n e - t u n i n g . An au tomated p e r s o n a l i z a t i o n p r o t o t y p e d e s i g n e d t o s e l e c t o p t i m a l v a l u e s was d e v e l o p e d and t e s t e d . i i i TABLE OF CONTENTS PAGE ABSTRACT . i i TABLE OF CONTENTS i v L I S T OF TABLES v i i L I S T OF FIGURES AND ILLUSTRATIONS v i i i ACKNOWLEDGEMENTS x I . INTRODUCTION . . . . . . . . . . 1 1 .1 P r e a m b l e 1 1 .2 G e n e r a l C o n c e p t s and C o n s i d e r a t i o n s . . . 1 1 .3 D e s i g n C o n s t r a i n t s 4 I I . A XEBEC PEN-BASED A P P L I C A T I O N 7 2 . 1 G e n e r a l C o m p a r i s o n o f R e c o g n i t i o n Schemes . 7 2 . 2 A X e b e c P e n - B a s e d Scheme 9 2 . 3 C h a r a c t e r S e t f o r a D e d i c a t e d E n v i r o n m e n t 10 I I I . THE B U I L D I N G BLOCKS OF CHARACTER RECOGNITION . . .16 3 . 1 D a t a A c q u i s i t i o n 16 3 . 1 . 1 G e n e r a l C o n s i d e r a t i o n s 16 3 . 1 . 2 S y s t e m C o n s t r a i n t s 17 3 . 1 . 2 . 1 H a r d w a r e . . . . . • . . 17 3 . 1 . 2 . 2 S o f t w a r e 18 3 . 2 P r e - P r o c e s s i n g 21 3 . 2 . 1 G e n e r a l C o n c e p t s . . . 21 i v PAGE 3.2.2 A M u l t i - L e v e l P r e - P r o c e s s i n g Scheme . 21 3.3 F e a t u r e E x t r a c t i o n 28 3.3.1 P u r p o s e . . . . . . . . . 28 3.3.2 I m p l e m e n t a t i o n C o n s t r a i n t ? 28 3.4 The C l a s s i f i c a t i o n Scheme . . . . . . . . . . . 36 3.4.1 I n t r o d u c t i o n 36 3.4.2 D i c t i o n a r y Format and O p e r a t i o n 39 3.5 T e s t i n g a t I n t e r m e d i a t e S t a g e s . . . . . . . . . . 47 3.5.1 S p u r i o u s D a t a a t S t r o k e E n d - P o i n t s . . . . . 47 3.5.2 D i r e c t i o n - C o d e V e c t o r C a l c u l a t i o n f o r S y s t e m P a r a m e t e r and D i c t i o n a r y E n t r y O p t i m i z a t i o n . . 49 3.5.3 D e v e l o p m e n t o f U s e r T r a i n i n g - A i d s 50 I V . F I N A L EVALUATION OF THE COMPLETED RECOGNITION SYSTEM 51 4.1 C l a s s i f i c a t i o n w i t h a R e s t r i c t e d D i c t i o n a r y . . . • • • 51 4.1.1 The L e a r n i n g C u r v e 53 4.1.2 P e r f o r m a n c e S e n s i t i v i t y t o U s e r C a t e g o r y 56 4.1.3 E f f e c t o f C h a r a c t e r S i z e on P e r f o r m a n c e 60 4.1.4 R i g h t - and L e f t - H a n d e d n e s s 63 4.1.5 T r a i n i n g f o r 95% R e c o g n i t i o n 65 4.1.6 C o n f u s i o n M a t r i c e s „ 67 4.1.7 S k i l l R e t e n t i o n . . . . . . . . . 70 4.1.8 C l a s s i f i c a t i o n R o b u s t n e s s f o r N o n - n o m i n a l Forms 72 4.2 C o n s t r u c t i o n o f P e r s o n a l i z e d Sys tems 74 4.2.1 I n t r o d u c t i o n 74 4.2.2 R e c o n f i g u r a t i o n o f t h e C l a s s i f i c a t i o n T r e e 75 v PAGE 4.2.3 T h r e s h o l d F a c t o r s • » - 78 4.2.4 S a m p l e - R a t e C o n s i d e r a t i o n s 79 4.2.5 C l i p p i n g Time 81 4.2.6 T i m e - O u t V a l u e 83 4.2.7 P l a n e N o n - U n i f o r m i t y 84 4.2.8 A u t o m a t i n g t h e P e r s o n a l i z a t i o n P r o c e s s . . . 87 4.3 P e r f o r m a n c e w i t h an E x t e n d e d R e s t r i c t e d D i c t i o n a r y . . . . . . 88 4.3.1 E f f e c t s upon R e c o g n i t i o n o f t h e O r i g i n a l C h a r a c t e r S e t . . . . 88 4.3.2 R e c o g n i t i o n P e r f o r m a n c e f o r t h e E x t e n d e d S y m b o l S e t . . . . . . 93 V . CONCLUDING REMARKS 96 5.1 Summary o f E x p e r i m e n t a l R e s u l t s . 96 5.2 A c h i e v e d D e s i g n O b j e c t i v e s . . . . . i . . . . . . . . . 101 5.2.1 F a v o r a b l e C h a r a c t e r i s t i c s . . . . . . . . . . . 101 5.2.2 E l i m i n a t i o n o f U n d e s i r a b l e C h a r a c t e r i s t i c s . 104 5.3 S y s t e m L i m i t a t i o n s 106 5.4 C o m p a r i s o n w i t h P u b l i s h e d R e s u l t s o f O t h e r A u t h o r s 107 5.5 Recommenda t ions f o r F u r t h e r R e s e a r c h no 5.6 C o n c l u s i o n s . . 116 REFERENCES 118 APPENDIX A E x a m p l e o f R e c o g n i t i o n S y s t e m P e r f o r m a n c e . ' . 123 B E x a m p l e o f D i s t o r t e d C h a r a c t e r Forms 124 C P h o t o g r a p h o f C h a r a c t e r R e c o g n i t i o n H a r d w a r e 125 v i L I S T OF TABLES TABLE PAGE I S y s t e m C h a r a c t e r i s t i c t s Drawn f r o m P u b l i s h e d L i t e r a t u r e t h a t D i r e c t l y I n f l u e n c e d D e s i g n O b j e c t i v e s . . . 5 I I E f f e c t s o f P r e - P r o c e s s i n g on D i g i t "6" 25 I I I A v e r a g e R e c o g n i t i o n P e r f o r m a n c e 54 I V P e r f o r m a n c e A f t e r 15 M i n u t e s o f T r a i n i n g 57 V ANOVA T a b l e f o r U s e r s f r o m D i f f e r e n t C a t e g o r i e s . . . . 59 V I Mean and V a r i a n c e o f D i f f e r e n c e D a t a 62 V I I C l a s s i c a l H y p o t h e s i s T e s t i n g . . . . . . 62 V I I I C o n f u s i o n M a t r i x f o r R e c o g n i t i o n P e r f o r m a n c e A f t e r T r a i n i n g - L a r g e D i g i t s . 68 I X C o n f u s i o n M a t r i x f o r R e c o g n i t i o n P e r f o r m a n c e A f t e r T r a i n i n g - S m a l l D i g i t s • 68 X The E f f e c t o f D i c t i o n a r y R e c o n f i g u r a t i o n 76 X I Summary o f P a r a m e t e r S e n s i t i v i t y i n a F r e e Form E n v i r o n m e n t . . . 78 X I I Summary o f A N S I V e r s u s E x t e n d e d D i c t i o n a r y T e s t R e s u l t s 92 X I I I H y p o t h e s i s T e s t i n g : V a r y i n g t h e D i c t i o n a r y 93 X I V H y p o t h e s i s T e s t i n g : V a r y i n g t h e S y m b o l S e t . . . . 94 v i i L I S T OF FIGURES AND ILLUSTRATIONS FIGURE PAGE 1.1 The B u i l d i n g B l o c k s o f P a t t e r n R e c o g n i t i o n . . . . . . . 2 2.1 E x a m p l e o f a T y p i c a l D i s p l a y U s i n g t h e C o m p u t e r - A s s i s t e d E l e c t r o n i c C i r c u i t P r o g r a m . . 12 2.2 E x t e n d e d G e s t u r e S e t C o n f i g u r e d f o r t h e D e m o n s t r a t i o n C i r c u i t Draw i n P a r t (b) . . . . . . . . 14 3.1 P l o t o f I n i t i a l and Maximum D e v i a t i o n o f X - , Y - and Z - P r e s s u r e V a l u e s 19 3.2 F l o w c h a r t o f t h e R e c o g n i t i o n S y s t e m ' s P r e - P r o c e s s i n g S t a g e . . . . 22 3.3 A G r a p h o f Raw X - P r e s s u r e D a t a f o r t h e H a n d p r i n t e d C h a r a c t e r , "P" . . . . . . . . . . . 24 3.4 A D e r i v e d T o p o l o g i c a l P l o t f o r t h e H a n d p r i n t e d C h a r a c t e r , "P" . . 30 3.5 E x a m p l e o f t h e E f f e c t o f A d d i n g S m a l l H y s t e r e s i s Zones a t Q u a n t i z e d D i r e c t i o n - Z o n e B o r d e r s 32 3.6 Summary o f Q u a d r a n t Q u a n t i z a t i o n Schemes . . . . . . . 33 3.7 S e v e r a l E x a m p l e s o f T r a i n i n g P r o g r a m O u t p u t . . . . . . . . . . . 35 3.8 E x a m p l e s D e m o n s t r a t i n g the E f f e c t o f M u l t i - L e v e l P r e - P r o c e s s i n g : - 37 3.9 E x a m p l e o f C l a s s i f i c a t i o n T r e e S t r u c t u r e . . • • • • » . . . . . . /$! 3.10 E x a m p l e s o f S t r o k e E n d - P o i n t D a t a 43 3.11 An I l l u s t r a t i o n o f I n h e r e n t D i c t i o n a r y Compac tness 45 3.12 A D e m o n s t r a t i o n o f t h e D i c t i o n a r y ' s T o l e r a n c e t o S y m b o l V a r i a t i o n s . 46 3.13 S t r u c t u r e o f t h e L i n k e d - L i s t C l a s s i f i c a t i o n Scheme 48 4.1 E x a m p l e o f a C o m p l e t e d R e c o g n i t i o n P e r f o r m a n c e S c o r i n g S h e e t . . . 52 4.2 A L e a r n i n g C u r v e o f S i n g l e T r i a l R e c o g n i t i o n P e r f o r m a n c e 55 v i i i FIGURE PAGE 4.3 T e s t i n g D a t a f o r S u b j e c t s whose R e c o g n i t i o n P e r f o r m a n c e A t t a i n e d 95% . . . . . . . . . 66 4.4 The E f f e c t o f Time F o l l o w i n g T r a i n i n g on R e c o g n i t i o n P e r f o r m a n c e .71 4.5 R e c o g n i t i o n P e r f o r m a n c e w i t h N o n - N o m i n a l I n p u t ^ - 73 4.6 E x a m p l e s o f V a r i a n t s f r o m N o m i n a l ANSI Forms 77 4.7 The E f f e c t o f C h a n g i n g P r e - S e t P r e s s u r e T h r e s h o l d s * • 80 4.8 The E f f e c t o f V a r y i n g Sample R a t e and C l i p p i n g Time . . . . . . . 82 4.9 The E f f e c t o f V a r y i n g T i m e - O u t V a l u e and P l a n e C o n f i g u r a t i o n . . . 85 4.10 S p e c i m e n s o f S u b j e c t s ' I and I I H a n d w r i t i n g 86 4.11 E x a m p l e o f D i s p l a y e d O u t p u t f r o m t h e A u t o m a t e d P e r s o n a l i z a t o n Scheme . 89 4.12 T e s t i n g w i t h an E x t e n d e d R e s t r i c t e d D i c t i o n a r y 91 5.1(a) D i f f e r e n t i a t i n g the Z e r o , O e r s t e d , and S i x . . . . . . 108 5.1(b) D i f f e r e n t i a t i n g t h e S i x and N i n e 108 5.2 N e g a t i v e E f f e c t s o f H y s t e r e s i s 112 i x ACKNOWLEDGEMENT I w o u l d l i k e t o e x p r e s s my s i n c e r e a p p r e c i a t i o n t o D r s . M . R . I t o and C F . S c h r a c k f o r t h e i r c o n s t a n t i n t e r e s t and e n c o u r a g e m e n t . I n a d d i t i o n , I w i s h t o e x t e n d my t h a n k s t o o t h e r f a c u l t y members f o r t h e i r h e l p f u l d i s c u s s i o n and t o V . Wong, V . L e i , T . L e u g n e r and D . D a i n e s who p r o v i d e d a s s i s t a n c e i n t h e i m p l e m e n t a t i o n phase o f t h i s t h e s i s . F i n a l l y , I am g r a t e f u l t o t h e many f a c u l t y , f e l l o w g r a d u a t e s t u d e n t s , and f r i e n d s f r o m o u t s i d e t h e d e p a r t m e n t who p a r t i c i p a t e d i n s y s t e m t e s t i n g e x p e r i m e n t s . F i n a n c i a l a s s i s t a n c e was p r o v i d e d t h r o u g h a P o s t g r a d u a t e S c h o l a r s h i p o f f e r e d b y the N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a . x I , INTRODUCTION 1 .1 P r e a m b l e The a b i l i t y t o s t o r e , m a n i p u l a t e and t r a n s f e r i n f o r m a t i o n i s e s s e n t i a l t o t he c r e a t i v e t h o u g h t p r o c e s s . U n t i l r e c e n t l y , man-machine i n t e r f a c e s i n t h e f i e l d o f c o m p u t i n g were d e s i g n e d w i t h t h e t e c h n i c a l l y -o r i e n t e d u s e r i n m i n d . Those who p o s s e s s e d m i n i m a l k n o w l e d g e o f m a c h i n e f u n c t i o n i n g were o f t e n r e q u i r e d t o a p p l y t h e m s e l v e s t o i n t e r - d i s c i p l i n a r y e n d e a v o r s . S u c c e s s r e s u l t e d f r o m t h e f i n e i n t e r a c t i o n o f t h e a r t i s t ' s s e n s i t i v i t y and t h e p r o g r a m m e r ' s a s t u t e n e s s . R e p o r t s d e s c r i b i n g t h e s t r u g g l e o f w r i t e r s , g r a p h i c a r t i s t s and m u s i c compose r s a p p e a r i n t h e l i t e r a t u r e [FRAN 7 8 ] . The q u a l i t y o f i n t e r a c t i o n depends h e a v i l y upon a v a i l a b l e i n p u t / o u t p u t d e v i c e s . T h e i r s u i t a b i l i t y t o the p a r t i c u l a r a p p l i c a t i o n i s o f g r e a t i m p o r t a n c e . I n t h i s t h e s i s , a p e n - p a p e r i n t e r f a c e i s e x p l o r e d t h r o u g h t h e i m p l e m e n t a t i o n o f a h a n d p r i n t e d c h a r a c t e r r e c o g n i t i o n scheme . E m p h a s i s i s p l a c e d upon t h e c o n s t r a i n t s o f r e a l - t i m e r e c o g n i t i o n i n a l i m i t e d ( e . g . m i c r o c o m p u t e r ) e n v i r o n m e n t t h a t r e f l e c t s t h e n o n - t e c h n i c a l u s e r ' s n a t u r a l t e n d e n c i e s . 1 .2 G e n e r a l C o n c e p t s and C o n s i d e r a t i o n s I n F i g . 1 .1 b e l o w a r e d e p i c t e d t h e m a j o r b u i l d i n g b l o c k s o f a p a t t e r n r e c o g n i t i o n s y s t e m . 2 Low l e v e l High l e v e l I/P Data A q u i s i -t i o n Pre-process-ing Feature Extrac-t i o n C l a s s i f -i c a t i o n ; O r i g i n of a message or d i r e c t i v e Defined c o l l e c t i v e l y as the Analysis stage F i g . 1 . 1 The B u i l d i n g B l o c k s o f P a t t e r n R e c o g n i t i o n Consequence of a message or d i r e c t i v e The r e c o g n i t i o n p r o c e s s i s an a t t e m p t t o p r o g r e s s ! v e l y i m p r o v e the d e s c r i p t i o n o f a c q u i r e d d a t a . I n i t s l o w e s t f o r m , t h e " m e s s a g e " i s o f t e n a b i n a r y d i g i t s t r e a m ; a t i t s h i g h e s t l e v e l i t may d e f i n e t h e f u l f i l l m e n t o f a d i r e c t i v e . A t i n t e r m e d i a t e s t a g e s , t h r o u g h t h e a p p l i c a t i o n o f d e f i n i t e r u l e s and c r i t e r i a , t h e i n f o r m a t i o n i s i n c r e a s i n g l y d e v e l o p e d . I t i s t h i s p r o c e d u r a l p r o c e s s t h a t d e f i n e s a p a t t e r n r e c o g n i t i o n s c h e m e . I n g e n e r a l , a r e c o g n i t i o n s y s t e m w i l l a d h e r e t o two b a s i c p r i n c i p l e s : a) a l l v a l i d i n p u t s must p r o v i d e p r e d i c t a b l e r e s u l t s i n a r e p e a t a b l e f a s h i o n . S t r i k i n g t h e l e t t e r " H " , f o r e x a m p l e , s h o u l d a l w a y s g e n e r a t e the same m a c h i n e r e s p o n s e . I n t h i s s e n s e t h e p r o c e s s i s u n i q u e ; b ) a g i v e n message w i l l a l w a y s c o r r e s p o n d t o a p a r t i c u l a r i n p u t and no two i n p u t s g e n e r a t e t h e same c o m m u n i c a t i o n . T o u d e f i n e s r e c o g n i t i o n as t h e c a t e g o r i z a t i o n o f l a r g e q u a n t i t i e s o f i n p u t d a t a i n t o v a r i o u s p r e - d e f i n e d c l a s s e s [TOU 7 2 ] . T h i s i s a c c o m p l i s h e d by e x t r a c t i n g o n l y t h o s e f e a t u r e s w h i c h a p p e a r s i g n i f i c a n t f r o m a b a c k g r o u n d o f i r r e l e v a n t d e t a i l . A m a j o r e f f o r t was e x p e n d e d i n t h i d i r e c t i o n d u r i n g t h e c o u r s e o f the t h e s i s . K a n a l h a s c e r t a i n s t r o n g f e e l i n g s r e g a r d i n g t h e c o n c e p t i o n o f a p r a c t i c a l s y s t e m . He e x p r e s s e s c o n c e r n o v e r t he a p p a r e n t h i g h e m p h a s i s o f t h e t h e o r e m - p r o o f a p p r o a c h t o p a t t e r n r e c o g n i t i o n . He p o i n t s o u t t h a t t h e r e i s a g r o w i n g t e n d e n c y t o q u e s t i o n , i n t h e name o f p r a c t i c a l i t y and s i m p l i c i t y , t h e n e e d f o r t h e o r e t i c a l s t u d i e s [KANA 74]. E l s e w h e r e i n t h e same a r t i c l e he a d v i s e s t h a t " e x p e r i m e n t a t i o n t o d e t e r m i n e s u i t a b l e f e a t u r e s i s t h e o n l y w o r t h w h i l e r o u t e " . The d e v e l o p m e n t o f t h e a u t h o r ' s s y s t e m was f a i r l y p r a g m a t i c i n a p p r o a c h . Where p o s s i b l e , e x p e r i m e n t s w e r e c o n d u c t e d t o v e r i f y a s s u m p t i o n s and s u p p o s i t i o n s . F r o m an i m p l e m e n t a t i o n p o i n t o f v i e w p e r h a p s t h e s i m p l e s t common a p p l i c a t i o n c o n c e r n s t h e r e c o g n i t i o n o f m a g n e t i c i n k c h a r a c t e r s t h a t a p p e a r o n bank c h e q u e s . S i n c e t h e y e x i s t o n l y i n n o m i n a l f o r m , s y m b o l d i s c r i m i n a t i o n i s f a c i l i t a t e d . A s a r e s u l t , t h e c l a s s i f i c a t i o n p r o c e d u r e i s s i m p l i f i e d . A t t h e o t h e r end o f t h e s p e c t r u m l i e s t h e p r o b l e m o f h a n d -p r i n t e d p o s t a l code r e c o g n i t i o n [GENC 6 8 ] . I n t h i s e n v i r o n m e n t c h a r a c t e r s a r e a l m o s t e n t i r e l y u n c o n s t r a i n e d . I f , f o r e x a m p l e , t h e s y m b o l "4-" i s t o be r e c o g n i z e d as n u m e r a l f o u r , how s h o u l d and "4" t h e n be c l a s s i f i e d ? Does "V b e l o n g t o t h e c l a s s o f n u m e r a l f o u r o r n u m e r a l n i n e ? F e a t u r e s e x t r a c t e d mus t be f l e x i b l e enough t o a l l o w v a r i a t i o n s w i t h i n a c h a r a c t e r y e t s u f f i c i e n t l y s p e c i f i c t o d i s t i n g u i s h amongst t h e v a r i o u s c h a r a c t e r s . R e s e a r c h u n d e r t a k e n i n t h i s t h e s i s r e l a t e s c l o s e l y t o t h e l a t t e r s y s t e m . C o n s t r a i n t s on s y m b o l f o r m a t i o n a r e m i n i m a l , t he number o f p o t e n t i a l v a r i a t i o n s f o r e a c h c h a r a c t e r a r e i n f i n i t e . The A N S I s t a n d a r d n u m e r i c s e t o f t e n d i g i t s [ANSI 74] t o g e t h e r w i t h n i n e d e d i c a t e d , s y m b o l s c o m p r i s e t h e r e p e r t o i r e . 1 .3 D e s i g n C o n s t r a i n t s I n T a b l e I a r e l i s t e d c h a r a c t e r i s t i c s o f s e v e r a l o f t h e more a c c o m p l i s h e d schemes t h a t d i r e c t l y o r i n d i r e c t l y i n f l u e n c e d the d e s i g n o f t h e a u t h o r ' s s y s t e m . U n f o r t u n a t e l y , i t i s d i f f i c u l t t o compare p u b l i s h e d r e s u l t s due t o a l a c k o f c o n s i s t e n t t e s t i n g d a t a and t o i n c o n s i s t e n c i e s i n t e s t i n g p r o c e d u r e s . C h a r a c t e r s e t s , f o r e x a m p l e , r ange f r o m t h e r e l a t i v e l y c o m p l e x Chinese a l p h a b e t [CASE 6 4 , STAL 75] t o t h e f a i r l y r e s t r i c t e d and unambiguous r e p e r t o i r e u s e d by H o s k i n g [HOSK 7 2 ] . T a b l e I p r o v i d e s a q u i c k r e f e r e n c e t o b o t h f a v o r a b l e and u n d e s i r a b l e c h a r a c t e r i s t i c s t h a t d i c t a t e d d e s i g n d e c i s i o n s f o r t h e p r o p o s e d s y s t e m . A l t h o u g h mos t comments a r e s e l f - e x p l a n a t o r y , a w o r d o f e x p l a n a t i o n o f t h e t e r m ' d y n a m i c ' (as o p p o s e d t o ' s t a t i c ' ) p r o c e s s i n g i s g i v e n . O p t i c a l c h a r a c t e r r e c o g n i t i o n schemes r e l y on s t a t i c p r o c e s s i n g t e c h n i q u e s s i n c e the s c a n n i n g o f i n p u t o f f - l i n e does n o t y i e l d t i m e s e q u e n c e i n f o r m a t i o n . C o n s i d e r t h e two s y m b o l s , a l p h a b e t i c " h " and n u m e r i c " b " . I f t h e y were a n a l y z e d , p o s t f a c t o , w i t h o u t any k n o w l e d g e o f t h e c h r o n o l o g i c a l o r d e r i n g o f s t r o k e s , i t i s u n l i k e l y t h a t t h e y w o u l d be r e a d i l y d i s t i n g u i s h a b l e . A d y n a m i c scheme w o u l d have l i t t l e d i f f i c u l t y i n d i s c r i m i n a t i n g b e t w e e n them s i n c e "o" was made i n a c l o c k w i s e f a s h i o n f o r t h e l e t t e r " b " y e t a n t i - c l o c k w i s e f o r d i g i t A s i m i l a r a rgument h o l d s f o r t h e p o t e n t i a l l y ambiguous p a i r , l e t t e r " S " and d i g i t " S " . 5 TABLE I . A SYSTEM CHARACTERISTICS DRAWN FROM PUBLISHED LITERATURE THAT DIRECTLY INFLUENCED DESIGN OBJECTIVES A U T H O R C H A R A C T E R I S T I C S [REFERENCE] FAVORABLE UNDESIRABLE H o s k i n g [HOSK 72] G r o n e r [GRON 68] B e r n s t e i n [BERN 68] B e r n s t e i n & H o w e l l [BERN 69] M i l l e r [ M I L L 69] L e d e e n [LEDE 73] C h u i [ C H U I 76] 1) R e a l - t i m e s y s t e m b e n e f i t s ( e . g . d y n a m i c p r o c e s s i n g ) 2) D a t a p r o c e s s e d on a p o i n t - b y - p o i n t b a s i s r e d u c i n g i n t e r m e d i a t e s t o r a g e and i m p r o v i n g r e s p o n s e t i m e 3) R e c o g n i t i o n p e r f o r m -ance i n d e p e n d e n t o f c h a r a c t e r s i z e 4) E l i m i n a t i o n o f s p u r i o u s e n d - p o i n t d a t a b e f o r e f e a t u r e e x t r a c t i o n b e g i n s 6) R e c o g n i t i o n P e r f o r m -ance i n d e p e n d e n t o f o v e r a l l c h a r a c t e r s l a n t and p o s i t i o n 7) E m p h a s i z e s i m p l i f i c a -t i o n o f p a t t e r n a n a l y s i s t h e r e b y r e d u c i n g c o m p u t i n g b u r d e n 8) P e r f o r m a n c e i n s e n s i -t i v i t y t o l o c a l v a r i a t i o n s . 1 ) R e l i a n c e upon a p a r t i c u l a r l y unambiguous c h a r a c t e r s e t 2) H i g h - s p e e d c o m p u t i n g f a c i l i t i e s r e q u i r e d 3) Many s t y l i s t i c c o n s t r a i n t s i m p o s e d 4) C h o i c e o f s t r o k e s r a t h e r t h a n c h a r a c t e r s as s y s t e m p r i m i t i v e s . T h i s n e c e s s i t a t e s d e t e r m i n i n g r e l a t i o n s b e t w e e n s t r o k e s . 5) E x e s s i v e l y h i g h memory r e q u i r e m e n t 6) C h a r a c t e r s i z e c o n s t r a i n e d ( t o y-") 7) A n a l y s i s i s n o t begun u n t i l s t r o k e c o n s t r u c -t i o n i s c o m p l e t e d 8) U s e r s a r e r e q u i r e d t o e n t e r e a c h member o f t he c h a r a c t e r s e t s e v e r a l t i m e s b e f o r e r e c o g n i t i o n may b e g i n 9) Use o f an e n v i r o n m e n t w h i c h i s l e s s n a t u r a l t h a n pen and p a p e r TABLE 1/8 SYSTEM CHARACTERISTICS DRAWIN FROM PUBLISHED LITERATURE THAT DIRECTLY INFLUENCED DESIGN O B J E C T I V E S , CONT'D A U T H O R C H A R A C T E R I S T I C S [REFERENCE] FAVORABLE UNDESIRABLE -C h u i C o n t ' d [CHUI 76] 9) M i n i m a l u s e r t r a i n i n g 10) R e s u l t s w e r e n o t p r o v e d s t a t i s t i c a l l y s i g n i f i c a n t C r a n e & S a v o i e [CRAN 77] 10) M i c r o - c o m p u t e r c o m p a t i b i l i t y 11) M i n i m a l p r e p r o c e s s i n g r e q u i r i n g a l a r g e number o f d i c t i o n a r y r e f e r e n c e s 12) S p e c i f i c e r r o r r a t e s u n d e r v a r y i n g c o n d i t i o n s w e r e n o t p u b l i s h e d 7 I I . A XEBEC PEN-BASED A P P L I C A T I O N 2.1 G e n e r a l C o m p a r i s o n o f R e c o g n i t i o n Schemes The common k e y b o a r d t e r m i n a l i s one o f t h e most w i d e l y u sed c o m p u t e r i n p u t d e v i c e s . I t d o e s , h o w e v e r , have s e v e r a l d r a w b a c k s : (a ) t h e m a j o r i t y o f p e o p l e do n o t know how t o t y p e and i t may be u n d e s i r a b l e t o t e a c h them e s p e c i a l l y i f d a t a i n p u t i s n o t t h e i r p r i m a r y t a s k ; (b ) use o f a n o n - c o n v e n t i o n a l c h a r a c t e r s e t r e q u i r e s s p e c i a l ( a n d u s u a l l y e x p e n s i v e ) k e y b o a r d s . The use o f f u n c t i o n p a d s m i g h t p r o v e c o n f u s i n g t o n o n - t e c h n i c a l u s e r s ; ( c ) m a n u a l r e t r a n s c r i p t i o n ( o r i g i n a t o r t o p a p e r t o k e y b o a r d ) e n t a i l s a d d i t i o n a l o v e r h e a d i n t e rms o f c o s t , d e l a y s and e r r o r s . U s i n g a p e n d e v i c e w o u l d e l i m i n a t e t h e s e d i f f i c u l t i e s s i n c e : (a ) h a n d p r i n t i n g i s an a l r e a d y e s t a b l i s h e d s k i l l f o r most u s e r s ; (b) a c c o m o d a t i o n o f n o n - s t a n d a r d c h a r a c t e r s i s e a s i l y e f f e c t e d t h r o u g h s o f t w a r e m o d i f i c a t i o n s w h i c h r e m a i n t r a n s p a r e n t t o t h e u s e r ; ( c ) t h e n e e d f o r h i g h o v e r h e a d r e t r a n s c r i p t i o n i s c o m p l e t e l y o b v i a t e d ; (d) t he p e n g e n e r a t e s i t s own o r i g i n a l c o p y w h i c h may be s t o r e d f o r f u t u r e r e f e r e n c e . U s i n g a k e y b o a r d r e q u i r e s a s e p e r a t e p r i n t i n g d e v i c e . One m i g h t s u s p e c t t h a t t h e i n f o r m a t i o n t h r o u g h p u t f o r h a n d w r i t i n g i s e x c e s s i v e l y s l o w b u t Devoe p r o v e s o t h e r w i s e by c i t i n g r e s u l t s f r o m c o n t r o l l e d e x p e r i m e n t s w h i c h show t h a t t he s p e e d o f h a n d p r i n t i n g n u m e r a l s 8 and c a p i t a l s compare f a v o u r a b l y w i t h t he k e y p u n c h i n g r a t e o f an u n s k i l l e d t y p i s t [ D E V 0 6 7 ] . T h i s s t a t e m e n t i s p a r t i c u l a r l y v a l i d i f i n p u t i s i n t e r s p e r s e d w i t h o t h e r t a s k s . C o m p u t e r - a i d e d d e s i g n o r c o m p u t e r - a s s i s t e d i n s t r u c t i o n r e p r e s e n t i d e a l p o t e n t i a l s i t u a t i o n s . N o t o n l y does h a n d p r i n t i n g p r o v i d e an e f f i c i e n t means o f d a t a t r a n s f e r , i t i s a l s o a n a t u r a l f o r m o f i n p u t . I t f u l f i l l s , a t l e a s t i n p a r t , t h e d e s i g n o b j e c t i v e t h a t t h e e n v i r o n m e n t be s u i t e d t o c o m f o r t a b l e human i n t e r a c t i o n . I n t he p a s t a m a j o r e f f o r t o f r e s e a r c h e r s h a s b e e n d i r e c t e d t o w a r d s o p t i c a l c h a r a c t e r r e c o g n i t i o n (OCR) schemes i n w h i c h d a t a a r e p r o c e s s e d o f f -l i n e . T h e r e a r e numerous i n h e r e n t d i s a d v a n t a g e s i n u s i n g t h i s f o r m o f p r o c e s s i n g : (a ) t i m e - s e q u e n c e o r d y n a m i c i n f o r m a t i o n w h i c h c o u l d be u s e f u l i n d i s c r i m i n a t i n g v a r i o u s c h a r a c t e r p a i r s ( e . g . l e t t e r " S " and d i g i t " 5 " ) i s n o t a v a i l a b l e ; (b) t h e p o s s i b i l i t y o f e r r o r d e t e c t i o n and s u b s e q u e n t c o r r e c t i o n a t t h e t i m e o f w r i t i n g i s s i g n i f i c a n t l y r e d u c e d ; ( c ) OCR e q u i p m e n t i s r e l a t i v e l y e x p e n s i v e and s p a c e - c o n s u m i n g ; (d ) r e c o g n i t i o n p e r f o r m a n c e i s d i r e c t l y dependen t upon s y m b o l , image q u a l i t y and i s t h e r e f o r e s e n s i t i v e t o p a p e r and i n k d e t e r i o r a t i o n , smudge m a r k s , d i r t , e t c . An a u t o m a t e d p e n - b a s e d s y s t e m t h a t f u n c t i o n s o n - l i n e e x h i b i t s : (a) a d v a n t a g e s a c c r u i n g t o d y n a m i c p r o c e s s i n g s u c h a s : i ) c h a r a c t e r d i s c r i m i n a t i o n v i a t i m e - s e q u e n c e i n f o r m a t i o n , e . g . , a o n e - s t r o k e l e t t e r "S" d i f f e r s f r o m t h e t w o -s t r o k e d i g i t " 5 " , i i ) v i s u a l o r a u d i o f e e d b a c k a l l o w i n g i m m e d i a t e c o r r e c t i o n o f m i s c l a s s i f i e d o r u n c l a s s i f i e d d a t a ; (b) a p o t e n t i a l l y l o w c a p i t a l i n v e s t m e n t and s p a c e - e f f i c i e n c y ; ( c ) i n s e n s i t i v i t y t o t h e c o n d i t i o n o r t r e a t m e n t o f t h e h a r d - c o p y f o l l o w i n g c h a r a c t e r f o r m a t i o n . Many p e n s y s t e m s employ t a b l e t s o r s c a n n e r s and t e n d t o b e e x p e n s i v e and b u l k y . They can a l s o u n r e a s o n a b l y c o n s t r a i n t h e u s e r b y d e f i n i n g s m a l l w r i t i n g s u r f a c e s o r b y i n c o r p o r a t i n g u n n a t u r a l w r i t i n g d e v i c e s . The scheme d e s c r i b e d i n t h e n e x t s e c t i o n i s a p e n - b a s e d s y s t e m t h a t does n o t s u f f e r t h e s e d r awbacks y e t does e x h i b i t a l l o f t h e a d v a n t a g e s l i s t e d a b o v e . 2.2 A X e b e c P e n - B a s e d Scheme X e b e c S y s t e m s ' A l p h a b e c 75 p r e s s u r e s e n s i t i v e b a l l - p o i n t p e n t o g e t h e r w i t h t h e a s s o c i a t e d a n a l o g u e t o d i g i t a l ( A / D ) . c o n v e r t e r was p u r c h a s e d as a r e s e a r c h t o o l . An i n t e r f a c e b o a r d was a l s o s u p p l i e d b u t f o u n d t o be f a i r l y i n c o m p a t i b l e w i t h t h e h o s t p r o c e s s o r . I n s e r t i n g a number o f c o n t r o l l i n e s and l o g i c g a t e s r e c t i f i e d t h e p r o b l e m . S o f t w a r e was n o t a c q u i r e d . A p h o t o g r a p h o f t h e p e n and A / D module a p p e a r s as A p p e n d i x C . A s t h e p e n i s moved i n t h e p l a n e o f t h e p a p e r , f o r c e s e q u a l and o p p o s i t e t o t h o s e a p p l i e d b y the w r i t e r a r e g e n e r a t e d a t the p e n - t i p . T h e s e d r a g f o r c e s r e l i a b l y d e f i n e c h a r a c t e r s h a p e . A n a r r a y o f p h o t o g r a p h i c a l l y e t c h e d s t r a i n gauges t h a t a r e bonded t o a f l e x i b l e d i a p h r a g m d e t e c t i n s t a n t a n e o u s v e r t i c a l and l a t e r a l p e n - t i p f o r c e s . As the p e n i s b r o u g h t i n t o c o n t a c t w i t h t h e w r i t i n g med ium, t h e d i a p h r a g m i s m i n u t e l y d e f o r m e d . The a s s o c i a t e d o r t h o g o n a l s t r a i n s a r e d i g i t i z e d and s u b s e q u e n t l y t r a n s m i t t e d t o p r o c e s s i n g a l g o r i t h m s . D e t a i l s o f t h e compound b r i d g e u s e d i n i s o l a t i n g the t h r e e - d i m e n s i o n a l f o r c e components a r e o u t l i n e d i n t h e l i t e r a t u r e [ C R A N 7 7 ] . By s a m p l i n g t h e v e r t i c a l p r e s s u r e component i t i s p o s s i b l e t o d e t e c t t h e " p e n - u p " ( i . e . , o f f t h e w r i t i n g medium) c o n d i t i o n . T h i s t y p e o f d y n a m i c i n f o r m a t i o n o f t e n a i d s i n d i s c r i m i n a t i n g c e r t a i n p o t e n t i a l l y ambiguous c h a r a c t e r p a i r s . P e n movement i s i n f e r r e d t h r o u g h a n a l y s i s o f i n s t a n t a n e o u s d r a g p r e s s u r e s t h a t r e f l e c t p e n - t i p d i r e c t i o n o f t r a v e l . Many p o s i t i o n - b a s e d schemes p r e - p r o c e s s t h e i r i n p u t d a t a t o d e t e r m i n e r e l a t i v e d i r e c t i o n s [CHUT 7 2 , M I L L 6 9 , POWE 7 3 ] ; t h i s i s n o t n e c e s s a r y when u s i n g a p r e s s u r e -t r a c k i n g p e n . S i n c e t h e p r o c e s s s o r does n o t r e c e i v e any i n f o r m a t i o n r e g a r d i n g pen p o s i t i o n , c o n s t r a i n t s a r e n e i t h e r p l a c e d on t h e w r i t i n g medium n o r on c h a r a c t e r s i z e . E a r l y e x p e r i m e n t a l r e s u l t s had i n d i c a t e d t h a t p o s i t i o n d a t a was n o t n e c e s s a r y and t h a t a t i m e s e q u e n c e o f p e n d i r e c t i o n s was s u f f i c i e n t t o p o s i t i v e l y i d e n t i f y most c h a r a c t e r s . The n e x t s e c t i o n d e a l s w i t h c h a r a c t e r - s e t d e f i n i t i o n f o r t he p r o p o s e d r e c o g n i t i o n s y s t e m . 2 . 3 C h a r a c t e r S e t f o r a D e d i c a t e d E n v i r o n m e n t A n u m e r i c s o n l y s y m b o l s e t c o n f o r m i n g t o t h e p r o p o s e d A N S I s t a n d a r d was u s e d i n e a r l y t e s t i n g . R e c o g n i t i o n p e r f o r m a n c e was so e n c o u r a g i n g t h a t an e x t e n s i o n t o t h e s e t was d e f i n e d . R a t h e r t h a n s e l e c t s y m b o l s a t r andom, a r e p e r t o i r e t h a t w o u l d have i m m e d i a t e a p p l i c a t i o n i n a scheme e x i s t i n g a t t he U n i v e r s i t y o f B r i t i s h C o l u m b i a was c o n f i g u r e d . A l t h o u g h t h e pen was n o t 11 i m p l e m e n t e d i n t h e c h o s e n e n v i r o n m e n t , t h e i m p o r t a n t a s p e c t s o f s u c h an a p p l i c a t i o n w e r e e x a m i n e d . The a p p l i c a t i o n i n v o l v e s c o m p u t e r - a i d e d e l e c t r o n i c c i r c u i t d e s i g n . U n d e r t h e o r i g i n a l i m p l e m e n t a t i o n an a b s o l u t e - p o s i t i o n j o y s t i c k / c r o s s - h a i r d e v i c e i s u s e d t o i d e n t i f y o r p o s i t i o n g r a p h i c a l o b j e c t s on a M e g a t e k r e f r e s h d i s p l a y ( r e f e r t o F i g . 2 . 1 f o r t y p i c a l o u t p u t ) . E l e c t r o n i c components and v a r i o u s s y s t e m commands a r e r e f e r e n c e d by f i r s t p o s i t i o n i n g t h e c r o s s - h a i r s o v e r d e f i n e d s u b - a r e a s and t h e n s t r i k i n g any c h a r a c t e r on t h e k e y b o a r d . The d e f i n e d a r e a ( t e r m e d the "menu") i s l o c a t e d t o t h e r i g h t o f t h e s c r e e n and i s n e c e s s a r i l y a l w a y s p r e s e n t . The pen w o u l d r e p l a c e t h e k e y b o a r d , t h e j o y s t i c k / c r o s s - h a i r a s s e m b l y , and the d i s p l a y e d menu. C e r t a i n s y m b o l d e s i g n g u i d e l i n e s were a d h e r e d t o i n e x t e n d i n g the c u r r e n t d i c t i o n a r y : , (a) w r i t i n g e a se ( f l u i d i t y o f p e n movement) was a d e s i r a b l e f e a t u r e ; (b) s y m b o l a m b i g u i t y was t o be a v o i d e d ( m a x i m i z i n g , where p o s s i b l e , i n t e r - c h a r a c t e r d i s c r i m i n a t i o n ) ; ( c ) e x t r a n e o u s o r u n n e c e s s a r y s t r o k e segments were n o t a l l o w e d ; (d) d i a g o n a l s t r o k e s were a v o i d e d s i n c e u n d e r t h e s e l e c t e d r o t a t e d q u a d r a n t q u a n t i z a t i o n p l a n e ( r e f e r t o S e c t i o n 3 . 3 ) r e c o g n i t i o n p e r f o r m a n c e i s s e n s i t i v e t o l o c a l v a r i a t i o n s i n t h i s r e g i o n ; (e) c h a r a c t e r s s h o u l d be e a s i l y u n d e r s t o o d and remembered ( T r i e s m a n and Kahneman a d v i s e d t h a t t h e use o f " f a m i l i a r s y m b o l s " s h o u l d be a p r i m e c o n s i d e r a t i o n ) . _ P r o f e s s o r s T r i e s m a n and Kahnemen a r e members o f t h e U n i v e r i s t y o f B r i t i s h C o l u m b i a ' s P s y c h o l o g y d e p a r t m e n t [ P r i v a t e c o m m u n i c a t i o n ] . 13 B e c a u s e o f the e x p r e s s e d i m p o r t a n c e o f c r i t e r i o n (e) the t e r m s p e c i a l c h a r a c t e r c o u l d be r e p l a c e d by t h e r i c h e r w o r d " g e s t u r e " w h i c h i m p l i e s more t h a n m e r e l y a m e m o r i z e d s y m b o l ; a g e s t u r e i s a n a t u r a l means o f e x p r e s s i o n . The g e s t u r e s e t shown i n F i g . 2 . 2 , f o r e x a m p l e , was d e s i g n e d f o r a u s e r w i t h an e l e c t r o n i c s b a c k g r o u n d . I n o r d e r t o i d e n t i f y a c a p a c i t o r , two p a r a l l e l p l a t e s a r e d r a w n . A c o i l e d w i r e s i g n i f i e s an i n d u c t o r . I n t h e same w a y , d i r e c t i v e s o r commands s h o u l d be m e a n i n g f u l l y c o n f i g u r e d f o r t h e a n t i c i p a t e d u s e r . A g a i n i n r e f e r e n c e t o F i g . 2 ; 2 , i n o r d e r t o d e l e t e a s y m b o l a l r e a d y i d e n t i f i e d , t he u s e r m e r e l y "d raws a l i n e t h r o u g h i t " on h i s h a r d c o p y . To r e v e r s e an e l e c t r o l y t i c c a p a c i t o r he draws an a r r o w f rom r i g h t t o l e f t , c o n t r a r y t o n o r m a l w r i t i n g d i r e c t i o n . F i g u r e 2 . 2 (b) shows t h e h a r d - c o p y c r e a t e d when t h e h - p a r a m e t e r m o d e l d e m o n s t r a t i o n c i r c u i t was drawn i n a s i m u l a t e d e x p e r i m e n t . T h a t i s , t h e c i r c u i t was drawn as shown and i n p u t t o t h e g e s t u r e r e c o g n i t i o n p r o g r a m w h i c h o u t p u t s r e c o g n i t i o n r e s p o n s e s b u t does n o t a c t i v a t e t h e c i r c u i t d e s i g n p r o g r a m . The " r e v e r s e " , " d e l e t e " and " e n d " d i r e c t i v e s a s w e l l a s s i x e l e c t r o n i c components w e r e r e f e r e n c e d d u r i n g t h e s e s s i o n a n d a r e c o g n i t i o n s c o r e o f 100% was r e c o r d e d . I n A p p e n d i x C , a p h o t o g r a p h o f s y s t e m h a r d w a r e shows t h e X e b e c p e n , c o m p l e m e n t a r y A / D c i r c u i t r y i n a s h i e l d e d b o x and a p r i s m - s h a p e d m e t a l b l o c k . The b l o c k i s a s u p p o r t / r e f e r e n c i n g d e v i c e w h i c h when u s e d i n c o n j u n c t i o n w i t h t h e pen f u n c t i o n s as an i n c r e m e n t a l c u r s o r . By d i p p i n g t h e p e n i n t o t h e m a c h i n e d c i r c u l a r o p e n i n g and a p p l y i n g a f o r c e a t t h e p e n - t i p , a d i s p l a y e d c u r s o r i s moved i n the d e s i r e d d i r e c t i o n a t a r a t e p r o p o r t i o n a l t o t h e m a g n i t u d e o f t h e a p p l i e d f o r c e . B e c a u s e o f t h e h i g h r e s o l u t i o n p o s s i b l e w i t h t h e s t r a i n g a u g e s , p o i n t s on t h e s c r e e n can be r e f e r e n c e d a c c u r a t e l y . S i n c e 14 ( a ) E x t e n d e d G e s t u r e S e t C o n f i g u r e d f o r t h e S i m u l a t i o n C i r c u i t D r a w n i n P a r t ( B ) COMPONENT OR DIRECTIVE R e s i s t o r C a p a c i t o r I n d u c t o r F i e l d E f f e c t T r a n s i s t o r V o l t a g e S o u r c e C u r r e n t S o u r c e D e l e t e G r a p h i c a l O b j e c t R e v e r s e F i n i s h / E n d GESTURE ~AA-® 4r (Rightgoing) E OR F ( b ) S i m u l a t i o n C i r c u i t I n v o l v i n g M o s t o f t h e G e s t u r e s I d e n t i f i e d A b o v e —-AA- , r ~ 1 1 J J 1 l i f ! 1 I J i < - = ! = <v> & < £ [Reverse] + T i i F i g u r e 2.2 Delete i ' I i i ! i .JL I E [END] 15 t h e h o s t p r o c e s s o r , a Nova 840 m i n i c o m p u t e r , accomoda te s fast : s a m p l i n g , mos t c u r s o r p o s i t i o n i n g t a s k s r e q u i r e l e s s t h a n one s e c o n d . U n d e r t h e p r o p o s e d i m p l e m e n t a t i o n t h e c u r s o r w o u l d a p p e a r a t some p r e - d e f i n e d o r i g i n on t h e s c r e e n e a c h t i m e a component i s r e f e r e n c e d i n a n t i c i p a t i o n o f t h e s u b s e q u e n t p o s i t i o n i n g t a s k . I f , f o r e x a m p l e , t h e g e s t u r e , " I I " , was d r a w n , t h e w o r d c a p a c i t o r ( a v i s u a l f e e d b a c k f o r t h e u s e r ) and a s e t o f c r o s s - h a i r s o r a c u r s o r w o u l d a p p e a r . S u b s e q u e n t p r e s s u r e a p p l i e d a t t h e pen t i p s h i f t s t h e d i s p l a y e d c u r s o r / c r o s s - h a i r s u n t i l t h e u s e r , h a v i n g p o s i t i o n e d t h e c u r s o r , r a i s e s t h e p e n . The p r o c e s s o r , d e t e c t i n g a n u l l v e r t i c a l p r e s s u r e , d i s p l a y s a c a p a c i t o r w i t h c o n n e c t i n g w i r i n g on t h e M e g a t e k r e f r e s h t u b e . S i m i l a r l y , when g e s t u r e - d e f i n e d d i r e c t i v e s r e q u i r i n g component r e f e r e n c i n g a r e i n p u t , t h e c u r s o r a p p e a r s a n d i s d i s p l a c e d b y s u b s e q u e n t p e n - t i p f o r c e s g e n e r a t e d b y t h e u s e r . The c o m p l e t e 19 s y m b o l r e p e r t o i r e ( i n c l u d i n g c u r s o r c o n t r o l ) was t e s t e d on s e v e r a l p a r t i c i p a n t s . They a l l f o u n d component and d i r e c t i v e r e f e r e n c i n g s i m p l e and n a t u r a l and c u r s o r p o s i t i o n i n g f a s t and a c c u r a t e . 16 I I I . THE BUILDING BLOCKS OF CHARACTER RECOGNITION 3.1 Data Acquisition 3.1.1 General Considerations Data acquisition i s the conversion of information from i t s raw state into a form suitable for input to subsequent analysis phases. Imperfections at this stage are directly reflected i n recognition performance. In the past, hardware to perform this task has involved one or more of sensors (e.g. the Rand tablet [BERN68, BERN69, GRON66, GRON68, MILL69]), scanners and various forms of digitizers [POWE70, POWE73] a l l implemented with some degree of success. From a human-factors standpoint the universally accepted pen and paper environment would provide an excellent interface. Previous attempts at applying similar principles to the computing environment were unsuccessful for a number of reasons. In some schemes, for example, users were forced to look away from the paper at CRT when writing [GR0N68, MILL69]. In others, non-marking or cumbersome pens were employed often restricting written information to the confines of "tablet" surfaces [CHUI76]. Efforts have recently been placed on improving the aesthetic appeal of the inter-face [EXPE78]. Unfortunately these devices are often prohibitively expen-sive. Xebec Corporation manufactures a pen whose characteristics closely approximate the requirements cited above. The hardware i s presently quite expensive since the item i s not commercially available. However, because of the system's inherent simplicity, a drastic reduction i n price could be realized i f the unit were mass-produced. 17 3 . 1 . 2 S y s t e m C o n s t r a i n t s  3 . 1 . 2 . 1 H a r d w a r e The Nova 840 f u n c t i o n i n g u n d e r D a t a G e n e r a l ' s R e a l - T i m e D i s k O p e r a t i n g S y s t e m and e q u i p p e d w i t h 32k 1 6 - b i t w o r d s o f random a c c e s s memory p r o v i d e d f a r more p r o c e s s i n g power t h a n was a c t u a l l y r e q u i r e d ; i t i s f e l t : t h a t t h e e n t i r e c h a r a c t e r / g e s t u r e r e c o g n i t i o n s y s t e m c o u l d p e r f o r m a d e q u a t e l y i n a m i c r o c o m p u t e r e n v i r o n m e n t . A r e a l - t i m e c l o c k was a d j u s t e d t o r e q u e s t i n t e r r u p t s e r v i c e e v e r y 5 m i l l i s e c o n d s . T h i s r a t e p r o v e d e x c e s s i v e once t h e s y s t e m was o p e r a t i o n a l b u t i t was n o t o b j e c t i o n a b l e d u r i n g i n i t i a l t e s t i n g . I n t h e e a r l y s t a g e s o f s y s t e m d e s i g n , raw d a t a were t r a n s f e r r e d t o m a g n e t i c t a p e o r i n t o d i s k f i l e s f o r s u b s e q u e n t a n a l y s i s . A l i n e - p r i n t e r and a s t o r a g e - t u b e d e v i c e a l l o w e d r e a l - t i m e raw d a t a m o n i t o r i n g and a p o i n t -a d d r e s s a b l e r e f r e s h d i s p l a y p r o v i d e d a g r a p h i c a l means o f v e r i f y i n g i n f o r m a t i o n a t i n t e r m e d i a t e s t a g e s o f t h e d e s i g n . A l t h o u g h t h e s e p e r i p h e r a l s w e r e u s e f u l d u r i n g t h e c o u r s e o f t he t h e s i s , t h e y do n o t s e r v e any p u r p o s e i n the f i n a l i m p l e m e n t a t i o n . The f i n a l s y s t e m e n v i s a g e d c o m p r i s e s t h e p e n , i t s A / D e l e c t r o n i c s , a scheme f o r v i s u a l f e e d b a c k o f t h e c l a s s i f i c a t i o n d e c i s i o n ( e . g . LED d i s p l a y ) and an i n e x p e n s i v e m i c r o c o m p u t e r . E a c h o f t h e component p r e s s u r e s was i n t e r r o g a t e d p e r i o d i c a l l y . I t was o b s e r v e d t h a t i n t h e " p e n - u p " c o n d i t i o n mean x - , y - , and z - p r e s s u r e v a l u e s a t t h e o u t p u t o f t h e A / D c o n v e r t e r were - 2 0 , - 1 2 and - 4 8 u n i t s r e s p e c t i v e l y ( e a c h u n i t c o r r e s p o n d s t o 1 5 / 2 v o l t s ) . They w e r e n o t z e r o as one m i g h t h a v e l i k e d . F u r t h e r m o r e , i t was d i s c o v e r e d t h a t t h e s e o f f s e t v a l u e s t e n d e d t o v a r y f r o m c h a r a c t e r s amp l e t o c h a r a c t e r s a m p l e . 18 An i n d i r e c t s o l u t i o n was a d o p t e d as a r e s u l t o f t h e f o l l o w i n g o b s e r v a t i o n : a l t h o u g h " o f f s e t " f l u c t u a t i o n s o v e r a l o n g t i m e i n t e r v a l w e r e a p p r e c i a b l e , v a r i a t i o n s o v e r t h e c h a r a c t e r f o r m a t i o n t i m e were n o t ( F i g . 3 . 1 ) . The f i r s t p e n - u p f o r c e v e c t o r o f e a c h c h a r a c t e r was t h e r e f o r e s a v e d and u s e d as o f f s e t t o n o r m a l i z e a l l s u b s e q u e n t s ample v a l u e s . D e a l i n g w i t h t h e p r o b l e m a t t h i s s t a g e s i m p l i f i e d p r e - p r o c e s s i n g and f e a t u r e e x t r a c t i o n c a l c u l a t i o n s . A p p l y i n g t h i s scheme, i m p l i c i t l y r e q u i r e s t h a t t h e p e n - t i p be i n i t i a l l y h e l d f r o m t h e w r i t i n g medium. None o f t h e s u b j e c t s f e l t h a n d i c a p p e d i n c o m p l y i n g t o t h e i m p o s e d c o n s t r a i n t . 3 . 1 . 2 . 2 S o f t w a r e H a r d w a r e i s s u p p o r t e d by d a t a - a c q u i s i t i o n s o f t w a r e w r i t t e n i n NOVA a s s e m b l y l a n g u a g e . O t h e r p o r t i o n s o f t h e s y s t e m p r o g r a m were w r i t t e n i n F o r t r a n t o m i n i m i z e c o d i n g t i m e and t o f a c i l i t a t e m o d i f i c a t i o n s . S e v e r a l o f t h e more s a l i e n t f e a t u r e s o f t h e s o f t w a r e a r e d i s c u s s e d h e r e . F u r t h e r d e t a i l s o f s y s t e m p r o g r a m s a r e a v a i l a b l e t h r o u g h t h e Depa r tmen t o f E l e c t r i c a l E n g i n e e r i n g a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . A 2 0 0 - w o r d c i r c u l a r b u f f e r was f i l l e d w i t h a c q u i r e d d a t a and e m p t i e d s i m u l t a n e o u s l y , t h u s s y n c h r o n i z i n g t h e v a r i o u s s t a g e s o f p a t t e r n a n a l y s i s . C o n c u r r e n c y o f p r o c e s s i n g , as o p p o s e d to a s e q u e n t i a l a c q u i s i t i o n f o l l o w e d by a n a l y s i s a p p r o a c h , m a i n t a i n e d r e s p o n s e t i m e a t a r e a s o n a b l e l e v e l and r e d u c e d i n t e r m e d i a t e d a t a b u f f e r i n g r e q u i r e m e n t s . The c o n c u r r e n c y a s p e c t does n o t i n i t s e l f d i c t a t e t h e n e e d f o r a c i r c u l a r b u f f e r . The n e c e s s i t y a r i s e s f r o m t h e r e q u i r e m e n t t h a t t h e o p t i m a l a c q u i s i t i o n p e r i o d must n o t e x c e e d 15 m i l l i s e c o n d s e v e n t h o u g h t h e a n a l y s i s o f e a c h s amp le r e q u i r e s an a v e r a g e o f 40 m i l l i s e c o n d s . W i t h o u t t h e c i r c u l a r N 2 X o -t—» O OJ > l_ </) cu X Y OBSERVATION CONCLUSION -50 -20 • -10 I I Inter-Character Pressure Fluctations are Large Relative to Intra-Character Fluctuations. I n i t i a l x-, y-, and z-"Pen-Up" Pressures are Representative of Successive Values within Any Character Formation Session. 5 I I X 2 3 4 5 6 7 Session Number '3:' denotes two i d e n t i c a l values for a given session. I denotes values which are within one unit of one another. Figure 3.1 Pl o t of I n i t i a l and Maximum Deviation Pressure Values (Resting State) VO 20 b u f f e r , a n a l y s i s w o u l d be i n t e r r u p t e d b y the a c q u i s i t i o n t a s k b e f o r e t h e c u r r e n t d a t a were f u l l y p r o c e s s e d . . I n c i d e n t a l l y , t he 15 m i l l i s e c o n d v a l u e was n o t s e l e c t e d a r b i t r a r i l y . U s i n g an a c q u i s i t i o n p e r i o d o f g r e a t e r t h a n 15 m i l l i s e c o n d s p r o v e d u n a c c e p t a b l e s i n c e i m p o r t a n t c h a r a c t e r f e a t u r e s went u n d e t e c t e d . R e d u c i n g t h e p e r i o d g e n e r a t e d a g r e a t d e a l o f r e d u n d a n t d a t a f o r e v e n the f a s t e s t o f w r i t e r s . The c h o s e n v a l u e was o p t i m a l f o r t he a u t h o r and s e v e r a l c o l l e a g u e s and i s a s o f t -w a r e d e r i v e d m u l t i p l e o f t he 5ms. i n t e r f a c e c l o c k . The a n a l y s i s p e r i o d o f 40 m i l l i s e c o n d s was e q u a l l y c o n s t r a i n e d . A l l h e a v i l y u s e d r o u t i n e s were coded i n t i m e - e f f i c i e n t a s s e m b l y l a n g u a g e . The more c o m p l i c a t e d a l g o r i t h m s were c o d e d i n F o r t r a n b u t a t t e m p t s w e r e made t o h a n d -o p t i m i z e t h e r e s u l t i n g o b j e c t c o d e . A r e d u c t i o n f r o m t h e 40 ms . v a l u e c o u l d o n l y have been a c h i e v e d by r e w r i t i n g t h e F o r t r a n r o u t i n e s i n a s s e m b l y c o d e . U n d e r t h e s e c o n d i t i o n s t h e s y s t e m r e s p o n s e t i m e was a p p r o x i m a t e l y 1 s e c o n d . None o f t h e t e s t s u b j e c t s c o m p l a i n e d o f e x c e s s i v e l y s l o w s y s t e m r e s p o n s e . D i c t i o n a r i e s u s e d i n t h e c l a s s i f i c a t i o n s t a g e a r e g e n e r a t e d w i t h t h e a i d o f s u p p o r t p r o g r a m s and a r e l o a d e d i n t o c o r e p r i o r t o e a c h r e c o g n i t i o n s e s s i o n . I n t h e " P e r s o n a l i z e d " a p p r o a c h d e t a i l e d i n S e c t i o n 4 . 2 , t h e mos t s u i t a b l e d i c t i o n a r y t o g e t h e r w i t h p e r t i n e n t : o p t i m a l p a r a m e t e r v a l u e s a r e a u t o m a t i c a l l y i n p u t t o t h e s y s t e m upon u s e r i d e n t i f i c a t i o n . S i n c e n e i t h e r t h e X e b e c pen n o r t h e M e g a t e k d i s p l a y p r o c e s s o r a r e s t a n d a r d d e v i c e s , s h o r t i n i t i a l i z a t i o n and d e v i c e h a n d l i n g r o u t i n e s were w r i t t e n t o accommodate t h e m . W i t h d a t a a c q u i s i t i o n c o m p l e t e and i n f o r m a t i o n f o r m a t t e d f o r s u b s e q u e n t a n a l y s i s , t h e n e x t s t a g e i n t h e c l a s s i f i c a t i o n s c h e m e , p r e -p r o c e s s i n g , assumes c o n t r o l . 21 3 . 2 P r e - P r o c e s s i n g 3 . 2 . 1 G e n e r a l C o n c e p t s P r e - p r o c e s s i n g u s u a l l y r e f e r s t o some f o r m o f i n f o r m a t i o n , m a n i p u l a t i o n a p p l i e d t o r e d u c e i n h e r e n t r e d u n d a n c i e s and d i s t o r t i o n s i n . t h e raw d a t a made, a v a i l a b l e a t t h e a c q u i s i t i o n s t a g e . P a t t e r n a n a l y s i s , as i t i s o f t e n r e f e r r e d t o , c o m p r i s e s b o t h t h e p r e - p r o c e s s i n g and t h e f e a t u r e e x t r a c t i o n s t a g e s and u l t i m a t e l y d e t e r m i n e s the s a l i e n t f e a t u r e s , o r g a n i z i n g them e f f i c i e n t l y i n p r e p a r a t i o n f o r t h e f i n a l d e c i s i o n - m a k i n g p r o c e s s i n w h i c h t h e unknown s a m p l e i s c l a s s i f i e d as a member o f a p r e - d e f i n e d c l a s s . I n o r d e r t o r e d u c e t h e o v e r a l l c o m p u t i n g b u r d e n o n l y s i g n i f i c a n t d a t a s h o u l d be a l l o w e d t o p r o g r e s s t o s u b s e q u e n t s t a g e s o f t h e r e c o g n i t i o n s cheme ; h e n c e t h e n e e d f o r p r e - p r o c e s s i n g . O v e r p r e - p r o c e s s i n g c o u l d , h o w e v e r , r e s u l t i n t h e l o s s o f i m p o r t a n t c h a r a c t e r f e a t u r e s , w h e r e a s a p p l y i n g t o o l i t t l e m i g h t d e g r a d e s y s t e m r e s p o n s e t o an: i n t o l e r a b l e l e v e l ™ A f l o w - c h a r t o u t l i n i n g the c h o s e n p r e - p r o c e s s i n g scheme a p p e a r s a s F i g . 3 . 2 . I n t h e f o l l o w i n g s e c t i o n , t h e e n t i r e p r o c e s s i s d e s c r i b e d i n d e t a i l . 3 . 2 . 2 A M u l t i - L e v e l P r e - P r o c e s s i n g Scheme P r e - p r o c e s s i n g c o m p r i s e s two a s p e c t s : s m o o t h i n g and d a t a r e d u c t i o n . I n most h a n d p r i n t e d c h a r a c t e r r e c o g n i t i o n s y s t e m s , c o n s i d e r a b l e q u a n t i t i e s o f i r r e l e v a n t d a t a r e s u l t f r o m : ( i ) w r i t i n g s u r f a c e i n c o n s i s t e n c i e s ; ( i i ) hand t r e m o r / s l i p p a g e ; ( i i i ) e l e c t r o n i c n o i s e and ( i v ) q u a n t i z a t i o n e f f e c t s ( p o s i t i o n d i s c r e t e n e s s , A / D c o n v e r s i o n ) . 22 Pre-processing, ("interrupt clock i s software 1 ... yes © .driven [jreduced quantity of data by a factor of 3 xs I i i ^ no V e r i f y i f user has started writing Discard —^  Fetch data next values data point © no C l i p 3 Data from Both End-points of A l l Strokes. s i m i l a r s i g n i f i c a n t l y d i f f e r e n t Feature Extraction Stage (with Hysteresis) Figure 3.2 Flowchart of the Pre-Processing Stage. L o c a l d a t a v a r i a t i o n s can o f t e n be e l i m i n a t e d b y a p p l y i n g p o i n t - a v e r a g i n g s m o o t h i n g a l g o r i t h m s [GRON56] . I n F i g . 3 . 3 a re p l o t t e d the s equence o f x - p r e s s u r e s g e n e r a t e d b y the Xebec p e n d u r i n g the h a n d p r i n t i n g o f l e t t e r " P " . The r e s u l t i n g g r a p h i s f a i r l y t y p i c a l o f numerous p r e s s u r e p l o t s made f o r v a r i o u s s y m b o l s . I t i s r e l a t i v e l y smooth and f r e e f r o m the p e r t u r b a t i o n s m e n t i o n e d above s i n c e : (a) t h e w r i t i n g medium was a common p a d o f p a p e r ( a s o p p o s e d t o a h a r d t a b l e t o r d i g i t i z e r s u r f a c e ) and t h e r e f o r e e f f e c t s o f i n c o n s i s t e n c i e s and p o s i t i o n d i s c r e t e n e s s w e r e n e g l i g i b l e ; (b ) t h e pen i t s e l f w e i g h s o n l y 6 ounces and i s f a i r l y e a s y t o u s e ; ( c ) a l l e l e c t r o n i c e q u i p m e n t i s s h i e l d e d and p r o t e c t e d f r o m t e m p e r a t u r e e f f e c t s ; (d) f i n a l l y , t h e i n h e r e n t m e c h a n i c a l i n e r t i a o f t h e s t r a i n -gauge a r r a y p r o b a b l y c o n t r i b u t e s to s m o o t h i n g t h e d a t a . I t was d e c i d e d t h a t s m o o t h i n g w o u l d n o t be n e c e s s a r y and t h a t t h e g a i n e d c o m p u t a t i o n t i m e w o u l d be a p p l i e d to d e t e r m i n i n g w h e t h e r i n c o m i n g d a t a a r e s i g n i f i c a n t t o t h e c l a s s i f i c a t i o n p r o c e s s . F i g . 3 . 2 d e s c r i b e s t h e d a t a r e d u c t i o n s t a g e o f p r e - p r o c e s s i n g . The a l g o r i t h m i s composed o f f i v e s e q u e n t i a l l y e x e c u t e d l e v e l s and t h e q u a n t i t y o f d a t a i s r e d u c e d by a f a c t o o f 8 . L e v e l 1 d e a l s w i t h v e r t i c a l ( i . e . 2) p r e s s u r e . A l t h o u g h u s e r s were a s k e d t o a l l o w the p e n - t i p t o t o u c h t h e w r i t i n g s u r f a c e o n l y d u r i n g c h a r a c t e r f o r m a t i o n , a number o f them h a d the t e n d e n c y t o t o u c h t h e p a p e r 1200 800'N Figure 3.3 A Graph of Raw x-pressure Data for the Handprinted Character, "P". c ZD 400 0 0) t_ z> <J) CD i_ O . i X <-t— o c 50 100 ^ 0 Time (msec) -400 -800 -1200 S3 b e f o r e m o v i n g t h e pen o r t o l e a v e t h e pen i n t r a i l i n g c o n t a c t f o l l o w i n g s y m b o l c o m p l e t i o n . As a r e s u l t , s p u r i o u s s t r o k e d i r e c t i o n s were i n f e r r e d and r e c o g n i t i o n p e r f o r m a n c e s u f f e r e d a c c o r d i n g l y . By d e f i n i n g a minimum v e r t i c a l p r e s s u r e t h r e s h o l d t h a t had t o b e e x c e e d e d b e f o r e d a t a were s a v e d , t h e s e s p u r i o u s l o w p r e s s u r e p a t t e r n s w e r e g e n e r a l l y d i s c a r d e d . A n u m e r i c a l v a l u e was f i n a l l y s e l e c t e d a f t e r h a v i n g t e s t e d s u b j e c t s t o d e t e r m i n e t h e maximum t h r e s h o l d t h a t c o u l d n o r m a l l y be t o l e r a t e d . H i g h e r v a l u e s e l i m i n a t e d p o t e n t i a l l y s i g n i f i c a n t d a t a . As a b y - p r o d u c t o f Z - t h r e s h o l d v e r i f i c a t i o n , d a t a g e n e r a t e d t h r o u g h a c c i d e n t a l p e n - t i p c o n t a c t w e r e a l s o e l i m i n a t e d . I n a c o n t r o l l e d e x p e r i m e n t , raw d a t a g e n e r a t e d d u r i n g t h e p r i n t i n g o f d i g i t s i x w e r e s t o r e d on a m a g n e t i c d i s k . These d a t a w e r e s u b s e q u e n t l y p r e - p r o c e s s e d u n d e r t h e Z - t h r e s h o l d c r i t e r i o n and t h e t o t a l number o f d a t a was o b s e r v e d to d e c r e a s e by a p p r o x i m a t e l y 5% f r o m 57 t o 5 4 . T h i s and f u r t h e r r e s u l t s a r e s u m m a r i z e d i n T a b l e I I and i l l u s t r a t e d i n F i g . 3 . 8 . TABLE I I EFFECTS OF PRE-PROCESSING ON D I G I T " 6 " SPECIMEN PRE-PROCESSING CRITERION % OF TOTAL NUMBER OF POINTS DISCARDED I N D I V I D U A L CUMULATIVE A none 0.0 0.0 B Z - t h r e s h o l d 5 . 3 5 . 3 C X , Y , Z - t h r e s h o l d 1 4 . 0 1 9 . 3 D X , Y , Z - t h r e s h o l d and e n d - p o i n t c l i p p i n g 2 4 . 6 4 3 . 9 26 The s e c o n d l e v e l o f d a t a r e d u c t i o n c o n c e r n s d r a g ( x and y ) p r e s s u r e s . I t was n o t e d t h a t s u b j e c t s w o u l d v e r y o f t e n a l l o w t h e p e n - t i p t o r e s t i n c o n t a c t w i t h t h e p a p e r b e f o r e s t a r t i n g t o w r i t e ; t h e v e r t i c a l t h r e s h o l d , was e x c e e d e d and d r a g f o r c e s were i n f e r r e d as m e a n i n g f u l c h a r a c t e r s t r o k e s . R e c o g n i t i o n p e r f o r m a n c e was a d v e r s e l y a f f e c t e d . A n a l y z i n g t h e raw d a t a r e v e a l e d t h a t a l t h o u g h v e r t i c a l p r e s s u r e was s u f f i c i e n t l y h i g h t o - e x c e e d the t h r e s h o l d , d r a g p r e s s u r e s r e m a i n e d f a i r l y m i n i m a l . T h i s f a c t i s n o t s u r p r i s i n g s i n c e the u s e r was n o t m o v i n g t h e p e n . X - and Y - t h r e s h o l d s w e r e t h e r e f o r e d e f i n e d and p r e - p r o c e s s i n g augmented t o i n c l u d e the c r i t e r i o n t h a t e i t h e r t h e X - o r Y - t h r e s h o l d ( i n a d d i t i o n t o t h e Z - t h r e s h o l d ) h a d a l s o t o be e x c e e d e d . P e r f o r m a n c e i m p r o v e d , e s p e c i a l l y f o r t h e i n e x p e r i e n c e d u s e r who c o m m i t t e d t h e u n i n t e n t i o n a l e r r o r f a i r l y o f t e n . As an added a d v a n t a g e t h e f r e q u e n c y o f s p u r i o u s e n d - p o i n t " h o o k s " and " t a i l s " p r o d u c e d by more e x p e r i e n c e d w r i t e r s was a l s o r e d u c e d . B y a p p l y i n g t h e above t e c h n i q u e t o the raw d a t a c o l l e c t e d f o r t h e d i g i t s i x a f u r t h e r 5 d a t a p o i n t s w e r e e l i m i n a t e d ( c f . T a b l e I I ) . U n i n t e n t i o n a l e n d - p o i n t d a t a were a f e a t u r e o f mos t h a n d p r i n t e d c h a r a c t e r s . A l t h o u g h some o f t h e s e s p u r i o u s fo rms a r e t o l e r a t e d by t h e d e s i g n o f t h e d i c t i o n a r y ( d i s c u s s e d i n S e c t i o n 3 . 4 ) , i t i s p r e f e r r e d t o remove n o n - s i g n i f i c a n t d a t a e a r l y i n t h e p r o c e s s o t h e r w i s e r e s p o n s e t i m e s u f f e r s . To t h i s e n d , l e v e l 3 i s a s i m p l e e n d - p o i n t d a t a e l i m i n a t o r . S t r o k e s a r e t r u n c a t e d ( c l i p p e d ) by t h r e e d a t a p o i n t s a t e i t h e r e n d . G r e a t e r t r u n c a t i o n augments t h e l i k e l i h o o d o f s i g n i f i c a n t d a t a b e i n g d i s c a r d e d w h e r e a s d e c r e a s i n g t h i s v a l u e r e d u c e s the l e v e l ' s e f f e c t i v e n e s s . An a n a l y s i s o f r e s u l t s u s i n g e x t r e m e X - , Y - , Z - t h r e s h o l d v a l u e s and c l i p p i n g f a c t o r s i s p r e s e n t e d i n C h a p t e r I V . 27 L e v e l s 1 , 2 and 3 a r e p r i m a r i l y d a t a r e f i n e m e n t t e c h n i q u e s w h i c h f u l f i l l a s e c o n d a r y r o l e o f r e d u c i n g t h e q u a n t i t y o f d a t a t r a n s m i t t e d t o l a t e r s t a g e s . L e v e l 4 i s a t r u e d a t a r e d u c t i o n t e c h n i q ue i n t h a t i t s m a j o r f u n c t i o n i s t o u n b u r d e n t h e s y s t e m o f r e d u n d a n t d a t a . U n d e r schemes t h a t f u n c t i o n w i t h p o s i t i o n a l i n f o r m a t i o n , a common d a t a - t h i n n i n g t e c h n i q u e i s t o d i s c a r d t h o s e d a t a p o i n t s w h i c h a r e n o t s u f f i c i e n t l y d i s p l a c e d f r o m t h e p r e v i o u s l y a c c e p t e d p o i n t . U s i n g t h e X e b e c p e n , t h e c o r r e s p o n d i n g a l g o r i t h m w o u l d be t o a c c e p t t h e d a t a i f t h e change i n e i t h e r o f t h e d r a g ( i . e . , l a t e r a l ) p r e s s u r e s , as compared t o t h e p r e v i o u s l y a c c e p t e d p r e s s u r e s , was s i g n i f i c a n t . D a t a w o u l d be d i s c a r d e d i f t h e changes i n both . X - and Y -p r e s s u r e s w e r e l e s s t h a n some p r e - d e f i n e d t h r e s h o l d . A s l i g h t d i f f i c u l t y a r i s e s i n t h a t t h e r e e x i s t s c a s e s w h e r e l a r g e X - and Y - p r e s s u r e e x c u r s i o n s a r e n o t i n d i c a t i v e o f p e n - t i p d i r e c t i o n c h a n g e . F o r e x a m p l e , d r a g p r e s s u r e changes a t l i n e segment e n d - p o i n t s may be a p p r e c i a b l e e v e n t h o u g h new d i r e c t i o n i n f o r m a t i o n i s n o t g e n e r a t e d . D a t a -e x h i b i t i n g l a r g e changes i n b o t h X - and Y - p r e s s u r e s h o u l d t h e r e f o r e be s a v e d o n l y i f t h e r a t i o o f p r e s s u r e s , i . e . t h e i m p l i e d s t r o k e d i r e c t i o n , i s a l s o s u b s t a n t i a l l y d i f f e r e n t f r o m t h e p r e v i o u s r a t i o . C o n s e q u e n t l y , L e v e l 4 r e s o l v e s t o a t e s t o f d r a g p r e s s u r e r a t i o s . S i n c e i n f e r r e d d i r e c t i o n s a r e v e r y c o a r s e l y q u a n t i z e d a t t h e f e a t u r e e x t r a c t i o n , s t a g e , s m a l l changes a r e r e l a t i v e l y u n i m p o r t a n t . O n l y i f t h e change i n p r e s s u r e r a t i o i s s i g n i f i c a n t a r e d a t a p a s s e d t o s u b s e q u e n t s t a g e s o f a n a l y s i s . A t t h i s p o i n t , s a l i e n t f e a t u r e s a r e s e l e c t e d f r o m t h e r e m a i n i n g d a t a . B u t b e f o r e d e s c r i b i n g t h i s s t a g e i n d e t a i l , a f i n a l l e v e l o f d a t a r e d u c t i o n , w h i c h i s a p p l i e d a f t e r f e a t u r e e x t r a c t i o n , s h a l l be e x p l a i n e d b r i e f l y . S i n c e p o s i t i o n a l i n f o r m a t i o n i s n o t d i r e c t l y a v a i l a b l e f r o m t h e X e b e c d e v i c e , s e v e r a l c o n s e c u t i v e d a t a p o i n t s e a c h g e n e r a t i n g t h e same d i r e c t i o n - c o d e p r o v i d e no more i n f o r m a t i o n t h a n a s i n g l e p o i n t o f t h a t d i r e c t i o n - c o d e . S u c c e s s i v e e q u a l codes may t h e r e f o r e be s a f e l y d i s c a r d e d . L e v e l 5 i d e n t i f i e d i n F i g . 3 . 2 e l i m i n a t e s t h e s e r e d u n d a n c i e s i n d i r e c t i o n -code i n f o r m a t i o n . 3 . 3 F e a t u r e E x t r a c t i o n 3 . 3 . 1 P u r p o s e A t t h e F e a t u r e E x t r a c t i o n s t a g e , s a l i e n t f e a t u r e s o f t h e s a m p l e a r e c o m p u t e d . The t e c h n i q u e a p p l i e d must be s p e c i f i c enough t o a l l o w e x a c t and r a p i d d i s c r i m i n a t i o n a t t he c l a s s i f i c a t i o n s t a g e , y e t g e n e r a l enough t o t o l e r a t e u n i n t e n t i o n a l c h a r a c t e r v a r i a t i o n s . I n t he p a s t , a v a r i e t y o f methods have b e e n a p p l i e d t o t h e p r o b l e m . T o p o l o g i c a l f e a t u r e e x t r a c t i o n was e f f e c t i v e l y u s e d by T o u and G o n z a l e z [TOU72] w h o , by d i v i d i n g t h e p a r a m e t e r a r o u n d t h e c h a r a c t e r i n t o e i g h t s e c t i o n s , w e r e a b l e t o e x t r a c t i n f o r m a t i o n r e g a r d i n g c u s p s , c u r v a t u r e and i n f l e c t i o n s . E x a m p l e s o f g e o m e t r i c f e a t u r e e x t r a c t i o n a r e n o t e d i n t h e t e c h n i c a l l i t e r a t u r e [ L E D E 7 3 , L I N 7 4 , C H U I 7 6 ] . F e a t u r e s e x t r a c t e d g e n e r a l l y t a k e t h e a p p e a r a n c e o f a s t r i n g o f p r i m i t i v e e l e m e n t s ; t he s t r i n g i s a s t a t e m e n t a b o u t t h e s am p le i n . t h e l a n g u a g e o f t h e d e f i n e d grammar. S p e c i f i c g r a m m a t i c a l r u l e s g o v e r n t h e c o n s t r u c t i o n o f t h e s e s t a t e m e n t s and a re c o n s i d e r e d i n t h e f o l l o w i n g s e c t i o n . 3 . 3 . 2 I m p l e m e n t a t i o n C o n s t r a i n t s P o w e r s c o n c l u d e s t h a t s h o r t - t e r m pen d i r e c t i o n i n f o r m a t i o n w i t h o u t p o s i t i o n a l c u e s , " n e a r l y c h a r a c t e r i z e s n a t u r a l c h a r a c t e r s " [ P 0 W E 7 3 ] . The i m p l i c a t i o n t h a t r e c o g n i t i o n p e r f o r m a n c e c o u l d be i m p r o v e d i f f u r t h e r i n f o r m a t i o n w e r e s u p p l i e d i s s u b s t a n t i a t e d by Freeman who c l a i m s t h a t , "one r e a s o n f o r u s i n g more t h a n one p r o p e r t y f r e q u e n t l y i s t h a t t h e d e s i r e d p r e c i s i o n c a n n o t o t h e r w i s e be a c h i e v e d " [ F R E E 6 1 ] . The p o s s i b i l i t y o f e x t r a c t i n g o t h e r t h a n d i r e c t i o n a l f e a t u r e s f rom d a t a g e n e r a t e d by t h e X e b e c pen was e x a m i n e d . E a r l y e x p e r i m e n t a l r e s u l t s i n d i c a t e d t h a t d a t a r e a d f r o m t h e p e n ' s s t r a i n gauges c o u l d be r e s o l v e d t o s t r o k e d i r e c t i o n . S i n c e p r e s s u r e s a r e s a m p l e d a t a c o n s t a n t r a t e any a s s u m p t i o n r e g a r d i n g p e n - t i p v e l o c i t y i m p l i c i t ! ; p r o v i d e s e s t i m a t e s o f p e n - t i p p o s i t i o n . S e v e r a l v e l o c i t y r e l a t i o n s w e r e e x a m i n e d b e a r i n g i n m i n d t h a t c a l c u l a t i o n s w o u l d be c o n s t r a i n e d b y t h e p r o p o s e d m i c r o c o m p u t e r e n v i r o n m e n t . Samples w e r e o b t a i n e d f r o m a v a r i e d p o p u l a t i o n and t o p o l o g i c a l g r a p h s p r e p a r e d a s s u m i n g c o n s t a n t h o r i z o n t a l o r v e r t i c a l o r a b s o l u t e m a g n i t u d e o f v e l o c i t y . A p l o t f o r c h a r a c t e r P a p p e a r s as F i g . 3 . 4 ; i t s d i s s i m i l a r i t y t o t h e d rawn c h a r a c t e r c o n t r a d i c t s t h e a s s u m p t i o n o f c o n s t a n t h o r i z o n t a l v e l o c i t y . The c o n s t a n t a b s o l u t e m a g n i t u d e o f v e l o c i t y a s s u m p t i o n o c c a s i o n a l l y g e n e r a t e d w o r t h w h i l e r e s u l t s , e s p e c i a l l y i n t h e c a s e o f c h i l d r e n who w r i t e f a i r l y s l o w l y . B u t i n g e n e r a l , f i n d i n g s w e r e d i s c o u r a g i n g , v a r y i n g f r o m p e r s o n t o p e r s o n and t e s t i n g s e s s i o n t o t e s t i n g s e s s i o n . I t was f i n a l l y d e c i d e d t o s h i f t t h e e m p h a s i s t o o p t i m i z i n g t h e o n l y i n f o r m a t i o n made d i r e c t l y a v a i l a b l e , pen d i r e c t i o n . As i n d i c a t e d e a r l i e r the s t r a i n - g a u g e a r r a y g e n e r a t e s h i g h r e s o l u t i o n f o r c e d a t a . S i n c e h a n d p r i n t e d c h a r a c t e r fo rms a r e i n h e r e n t l y n o n - n o m i n a l , i . e . l o c a l v a r i a t i o n s i n t h e fo rm o f u n i n t e n t i o n a l d a t a a r e common, f e a t u r e s e x t r a c t e d have t o be f a i r l y c o a r s e i n n a t u r e . A s m a l l Star t Y A Figure 3.4 A Derived Topological Plot for Handprinted Character, " P " , Under the Assumption of Constant Horizontal Speed. 31 s l a n t e d d i g i t t w o , f o r e x a m p l e , w i t h an e x t e n d e d t a i l s h o u l d be c l a s s i f i e d as b e l o n g i n g t o t h e same p a t t e r n c l a s s as a v e r y l a r g e two w i t h a s m a l l " h o o k " a t i t s h e a d . A human r e a d e r w o u l d c o r r e c t l y r e c o g n i z e b o t h w i t h l i t t l e d i f f i c u l t y ; t h e c l a s s i f i c a t i o n s y s t e m s h o u l d do no l e s s . I n t h e p r o p o s e d s y s t e m , h i g h r e s o l u t i o n d a t a a r e q u a n t i z e d i n a segmen ted d i r e c t i o n p l a n e . M i l l e r d i v i d e d h i s p l a n e i n t o e i g h t e q u a l d i r e c t i o n - s e g m e n t s and d e f i n e d e a c h s y m b o l by f i v e d i r e c t i o n - c o d e s [ M I L L 6 9 J . A p p l y i n g s u c h a t e c h n i q u e t o Xebec pen d a t a y i e l d e d u n a c c e p t a b l e r e s u l t s f o r c o m p l e x s y m b o l s s i n c e f i v e codes were i n s u f f i c i e n t t o a d e q u a t e l y d e s c r i b e a l l t h e i r i m p o r t a n t t o p o l o g i c a l f e a t u r e s . G r o n e r o p t e d f o r a u n i f o r m q u a d r a n t p l a n e ( i . e . , d i v i d e d i n t o f o u r e q u a l s egmen t s ) b u t d i d n o t l i m i t t h e number o f d i r e c t i o n codes [GRON66] . Complex s y m b o l s , t h e r e f o r e , g e n e r a t e d c o m p l e x d i r e c t i o n - c o d e s t a t e m e n t s . C r a n e and S a v o i e e m p l o y e d a r o t a t e d u n i f o r m q u a d r a n t p l a n e i n t h e i r r e c o g n i t i o n scheme [ C R A N 7 7 ] . A s i n g l e d i f f i c u l t y was n o t e d : d i a g o n a l l i n e s g e n e r a t e d v a r i a b l e d i r e c t i o n codes as t h e i n s t a n t a n e o u s f o r c e d i r e c t i o n f e l l f r o m one s i d e t o t h e o t h e r o f t h e 4 5 ° b o r d e r s . F i g . 3 . 5 i l l u s t r a t e s t h e m o d i f i e d r o t a t e d u n i f o r m q u a d r a n t p l a n e w h i c h was s e l e c t e d f o r t h e a u t h o r ' s s y s t e m . A s l o n g a s i n f e r r e d d i r e c t i o n c o o r d i n a t e s r e m a i n w i t h i n d e f i n e d h y s t e r e s i s z o n e s , t h e e x t r a c t e d q u a n t i z e d d i r e c t i o n code r e m a i n s u n c h a n g e d . A s s u m e , f o r e x a m p l e , 1 6 ° o f h y s t e r e s i s . I f a p r e v i o u s d i r e c t i o n was q u a n t i z e d t o q u a d r a n t " 1 " , s u c c e s s i v e c o o r d i n a t e s w o u l d have t o f a l l o u t s i d e the ± ( 4 5 + 8 ) ° e x t e n d e d segment i n o r d e r t h a t a d i f f e r e n t d i r e c t i o n code be g e n e r a t e d . The p r o p o s e d f e a t u r e e x t r a c t i o n a l g o r i t h m s w i t h and w i t h o u t h y s t e r e s i s a r e s u m m a r i z e d i n F i g . 3 . 6 . The a d d i t i o n a l o v e r h e a d t h a t r e s u l t s I„ Without Hysteresis D i r e c t i o n Codes : 1,2,1,2,*-1,1,2,2 are Generated Chronologically for the Nominally Horizontal B-stroke of D i g i t Five. 32 I I . With 16° of Hysteresis The Single D i r e c t i o n Code, 1, i s Generated. C l a s s i f i c -ation Under Scheme II i s Simpler and Faster Than Under Scheme I. / Figure 3.5 Example of the E f f e c t of Addling Small Hysteresis Zones at Quantized Direction Zone Borders. 33 I . W i t h o u t H y s t e r e s i s DIRECTION INFERRED FROM PRESSURE - 1 P Y (6 = t a n A - ± - ) X Q U A D R A N T D E S C R I P T O R P x>0 , P y>0 P x<0 , P Y>0 px ! 0 . P Y±0 0 <_ t a n 6 ^ 1 1 3 1 3 1 < t a n 0 < oo 2 2 4 4 LEGEND: _ _ . v , . P = P r e s s u r e i n X - d i r e c t i o n A. P Y = P r e s s u r e i n Y - d i r e c t i o n 6 = I n f e r r e d d i r e c t i o n measu red c o u n t e r - c l o c k w i s e f r o m t h e h o r i z o n t a l , i . e . ft O t h e r = P r e v i o u s d i r e c t i o n n o t i n Q u a d r a n t s d e f i n e d by b o r d e r t h e r e f o r e q u a n t i z e i g n o r i n g h y s t e r e s i s I I . W i t h H y s t e r e s i s DIRECTION INFERRED FROM PRESSURE P (6 = t a n " 1 - ^ j X Q U A D R A N T D E S C R I P T O R P x > 0 , P y > 0 P X > 0 ' P Y - 0 px 1 0 * P Y ±0 PREVIOUS QUADRANT PREVIOUS QUADRANT PREVIOUS QUADRANT PREVIOUS QUADRANT 1 2 OTHER 3 2 OTHER 1 4 OTHER 3 4 OTHER 0 <_ t a n 6 <_ . 754 1 1 ft 3 3 * 1 1 ft 3 3 * . 7 5 4 < t a n 0 ^ 1 . 3 2 7 1 2 ft 3 2 * 1 4 * 3 4 1 .327 <_ t a n 6 < °° 2 2 * 2 2 ft 4 4 ft 4 4 ft w h e r e t a n 4 5 ° - 8 ° = 0 . 7 5 4 t a n 4 5 ° + 8 ° = 1 .327 F i g u r e 3 . 6 Summary o f Q u a d r a n t Q u a n t i z a t i o n Schemes i n i m p l e m e n t i n g t h e h y s t e r e s i s f e a t u r e i s o f f s e t by t h e s u p e r i o r r e s u l t s o b t a i n e d . C h u i s u g g e s t e d u s i n g a n o n - u n i f o r m q u a n t i z a t i o n p l a n e i n w h i c h o c t a n t s w e r e o f u n e q u a l s i z e [ C H U I 7 6 ] . U n d e r h i s i m p l e m e n t a t i o n , t h e o c t a l segments c o v e r i n g d i a g o n a l d i r e c t i o n s w e r e e n l a r g e d t o accommodate i n c r e a s e d d i r e c t i o n v a r i a t i o n s o f o b l i q u e l i n e s . T h i s i d e a c o u l d be t a i l o r e d , t o t h e p a r t i c u l a r s y m b o l s e t f o r w h i c h t h e r e c o g n i t i o n s y s t e m i s d e s i g n e d . R e s u l t s o b t a i n e d u s i n g a p l a n e w i t h an i n c r e a s e d t o l e r a n c e to i m p r e c i s e h o r i z o n t a l o r v e r t i c a l s t r o k e s a r e e x a m i n e d i n S e c t i o n 4 . 2 . 7 . S i n c e s u b j e c t s w e r e made aware o f t h e c a l c u l a t e d d i r e c t i o n - c o d e v e c t o r , t h e q u a d r a n t s w e r e r e - l a b e l e d i n a more m e a n i n g f u l f a c h i o n . Segments 1 , 2 , 3 and 4 o f F i g . 3 . 5 a r e h e r e a f t e r r e f e r r e d t o as R i g h t (R) , UP (U) , L e f t . (L ) and Down(D) r e s p e c t i v e l y . D i r e c t i o n c o d e s as d e f i n e d do n o t d e s c r i b e a m u l t i - s t r o k e c h a r a c t e r c o m p l e t e l y . I n o r d e r t o i m p r o v e s y m b o l d e s c r i p t i o n , n o t e i s t a k e n o f when t h e p e n i s r a i s e d f r o m t h e w r i t i n g s u r f a c e and t h i s i n f o r m a t i o n i s i n c l u d e d i n t h e d i r e c t i o n - c o d e v e c t o r . I n F i g . 3 .7 a p p e a r t h r e e p h o t o g r a p h s o f r e c o g n i z e r o u t p u t . The d i r e c t i o n - c o d e v e c t o r , a d e r i v e d c o m p o s i t e p r e s s u r e t r a c e , and t h e c l a s s i f i c a t i o n d e c i s i o n a r e d i s p l a y e d o n t h e M e g a t e k CRT. A t t h e p r e s e n t t i m e , o n l y t h e d i r e c t i o n codes a r e i m p o r t a n t . I n P l a t e ( a ) , t h e t i m e - o r d e r e d q u a n t i z e d d i r e c t i o n s e q u e n c e i s "RDLDRO" . The f i n a l " 0 " i n d i c a t e s t h a t t he p e n was l i f t e d f r o m t h e w r i t i n g medium. Such a s equence i s i n t u i t i v e l y r e a s o n a b l e f o r d i g i t two w h i c h b e g i n s w i t h a r i g h t w a r d (R) s t r o k e f o l l o w e d by a downward s t r o k e and so o n . P l a t e ( b ) , n u m e r i c " 3 " , i s e x p l a i n e d i n a s i m i l a r f a s h i o n . The f i n a l p h o t o g r a p h , P l a t e ( c ) i s a l i t t l e more c o m p l i c a t e d . The w r i t e r was i n s t r u c t e d t o d raw " 0 " t h e n t o t a k e t h e p e n f r o m t h e p a p e r and t o c r o s s a 35 SLOPE CODE VECTOR ROLftOLO SPECIMEN A SLOPE CODE VECTOR PRESS.INTERPRETATION OF, CHAR. 0 P L A T E ( c ) F i g u r e 3 . 7 E x a m p l e s o f T r a i n i n g P r o g r a m ' s O u t p u t d i a g o n a l l i n e t h r o u g h i t ( t h i s c h a r a c t e r i s c a l l e d t h e t e c h n i c a l z e r o o r t h e o e r s t e d ) . The p e n - o f f c o n d i t i o n i s n o t e d on two o c c a s i o n s , once b e f o r e t h e d i a g o n a l and a g a i n a t s y m b o l c o m p l e t i o n ; t h i s e x p l a i n s the d i r e c t i o n - c o d e v e c t o r " L D R U O L O " . D i r e c t i o n code r e d u c t i o n was m e n t i o n e d when d i s c u s s i n g t h e m u l t i -l e v e l p r e - p r o c e s s i n g scheme . I t m e r e l y v e r i f i e s t h a t no two c o n s e c u t i v e d i r e c t i o n codes a r e i d e n t i c a l and d i s c a r d s one o f them i f t h e y a r e . F o r e x a m p l e , t h e p a r t i a l l y p r o c e s s e d d i r e c t i o n - c o d e v e c t o r f o r d i g i t t w o , "RRRDDLDDDRO", w o u l d be r e d u c e d t o " R D L D R O " . Now t h a t t h e r e a d e r i s aware o f how d i r e c t i o n codes a r e d e t e r m i n e d , t h e d i g i t s i x a n a l y s i s p r e s e n t e d e a r l i e r may be v i e w e d f r o m a d i f f e r e n t p e r s p e c t i v e . P l a t e (A) o f F i g . 3 . 8 i l l u s t r a t e s t h e p r o c e s s o r ' s o u t p u t b e f o r e p r e - p r o c e s s i n g ; t h e d i r e c t i o n c o d e , "DRULDRULDRDR" i s l o n g and c o m p l e x . P l a t e (B) d e p i c t s t he e f f e c t o f a p p l y i n g Z - t h r e s h o l d t e s t i n g ; t h e f i n a l r i g h t w a r d s t r o k e d e t e c t e d i n S p e c i m e n A i s e l i m i n a t e d . . X - , Y - and Z - t h r e s h o l d t e s t i n g a r e a p p l i e d i n P l a t e ( C ) ; t h e i n i t i a l and f i n a l downward s t r o k e s e v i d e n t i n P l a t e (B) a r e o m i t t e d . I n t h e f o u r t h e x a m p l e , c l i p p i n g a t s t r o k e e n d - p o i n t s i s a l s o p e r f o r m e d . The r e s u l t i s t h e d i r e c t i o n code v e c t o r , " L D R U L " , n o m i n a l l y d e s c r i b i n g n u m e r i c s i x and i n a f o r m s u i t a b l e f o r e n t r y t o the f i n a l s t a g e o f t h e r e c o g n i t i o n p r o c e s s , c l a s s i f i c a t i o n . 3 . 4 The C l a s s i f i c a t i o n Scheme 3 . 4 . 1 I n t r o d u c t i o n The f i n a l p h a s e i s t h e d e c i s i o n - m a k i n g s t a g e i n w h i c h t h e unknown s a m p l e i s f i n a l l y c l a s s i f i e d i n t o one o f a f i x e d number o f p r e - d e f i n e d c l a s s e s . A v a r i e t y o f c l a s s i f i c a t i o n t e c h n i q u e s have b e e n u s e d i n the p a s t , S P E C I M E N .A S L O P E C O D E V E C T O R D R U L D R U L D R D R ' P R E S S U R E I N T E R P R E T A T I O N O F C H A R A C T E R * 5 ate (B) • S P E C I M E N B S L O P E C O D E V E C T O R D R U L D R U L D R D P R E S S U R E I N T E R P R E T A T I O N O F C H A R A C T E R 5 S P E C I M E N C S L O P E C O D E V E C T O R R U L D R U L D R P R E S S U R E I N T E R P R E T A T I O N O F C H A R A C T E R 5 S P E C I M E N D S L O P E C O D E V E C T O R L D R U L P R E S S U R E I N T E R P R E T A T I O N O F C H A R A C T E R E F i g u r e 3 . 8 E x a m p l e s D e m o n s t r a t i n g t h e E f f e c t o f M u l t i - l e v e l  P r e - p r o c e s s i n g . " ( S p e c i m e n A i s t h e r a w s a m p l e , s p e c i m e n D i s t h e f u l l y p r e - p r o c e s s e d v e r s i o n . ) 38 a number of them are summarized below. The table look-up method necessitates a perfect match of input character features to one of a number of pre-defined prototypes. In general, clas s i f i c a t i o n performance depends directly upon the number of table entries. Since the form of handprinted characters i s loosely constrained, table size may have to be prohibitively large for the minimal (i.e., microcomputer) environment under consideration. This statement is especially true for a "many user" environment. The best-match or nearest neighbour approach i s a promising alternative since table size may be reduced appreciably. Although the sample feature string must s t i l l be compared to pre-selected prototypes, the number of comparisons i s reduced since only a subset of a l l variations must be e x p l i c i t l y defined.A "degree of similarity" test i s applied and the best match (which may i n fact be exact) i s chosen; Miller [MILL69] and I'chikawa [ICHI74] apply the Lee distance metric [BATC 74] to this end. However, because of the inherently non-parameterized or unstructured nature of the best-match method, the search for a best match usually requires comparison against a l l prototypes. Furthermore, the calculation of the defined measure of similarity i s more complex than a simple exact-match comparison. These two factors contribute to a slow system response . The author chose to pursue a different approach. Unknown samples are classified by having successive pen direction data move a pointer-through a tree-like structure. As pressure information i s analysed, the pointer is moved increasingly closer to the f i n a l classification decision. At least one other author has implemented a simpler hardware version of this scheme and reports moderate success [CRAN77]. Justification for such a choice i s given below. 39 I n a r e a l - t i m e l i m i t e d r e s o u r c e e n v i r o n m e n t , e f f i c i e n t c o r e usage and f a s t s y s t e m r e s p o n s e a r e d e s i r a b l e . As i n d i c a t e d a b o v e , t h e e x a c t -ma tch t e c h n i q u e n e c e s s i t a t e s an e x h a u s t i v e l i s t i n g o f p o s s i b l e c h a r a c t e r v a r i a t i o n s and thus memory r e q u i r e m e n t s a r e u s u a l l y h i g h . A b e s t - m a t c h scheme n e c e s s i t a t e s a ma jo r CPU e f f o r t t o p e r f o r m t h e r e p e a t e d n o n - t r i v i a l m e t r i c c a l c u l a t i o n s . F u r t h e r m o r e , c o m p a r i s o n s c a n n o t n o r m a l l y be begun u n t i l a l l c h a r a c t e r ( o r s t r o k e ) d a t a a r e a v a i l a b l e . P o o r s y s t e m r e s p o n s e i s t h e r e f o r e t h e m a j o r d rawback o f a b e s t - m a t c h c l a s s i f i e r . The p r o p o s e d scheme i s v e r y c o r e e f f i c i e n t r e q u i r i n g l e s s t h a n 250 w o r d s f o r an ANSI n u m e r i c s d i c t i o n a r y . S y s t e m r e s p o n s e i s good s i n c e on t h e a v e r a g e o n l y f o u r p o i n t e r u p d a t e s a r e r e q u i r e d p e r c h a r a c t e r and a l l e x c e p t t h e f i n a l u p d a t e a r e p e r f o r m e d c o n c u r r e n t l y w i t h t he a c q u i s i t i o n p r o c e s s . Many a u t h o r s choose t o d i v i d e i n p u t c h a r a c t e r s i n t o t h e i r a s s o c i a t e d s t r o k e f o r m s . A f t e r c l a s s i f y i n g e a c h s t r o k e , t h e e n t i r e c h r o n o l o g i c a l s t r o k e s equence i s p a s s e d t o a s e c o n d s t a g e o f c l a s s i f i c a t i o n w h e r e a f i n a l d e c i s i o n i s r e n d e r e d . I n t h i s t h e s i s , c h a r a c t e r s a r e t r e a t e d as s i n g l e u n i t s . The d i r e c t i o n - c o d e v e c t o r c o m p r i s e s a s e r i e s o f i n f e r r e d d i r e c t i o n s w h i c h a r e p u n c t u a t e d by " p e n - o f f " i n d i c a t o r s ( r e p r e s e n t e d b y " 0 " ) . P e n - o f f d a t a a r e t r e a t e d as a f o r m o f d i r e c t i o n code i n f o r m a t i o n . T h i s f o r m o f u n i - l e v e l c l a s s i f i c a t i o n i s s i m p l e and t i m e - e f f i c i e n t . 3 . 4 . 2 D i c t i o n a r y F o r m a t and O p e r a t i o n A s a c h a r a c t e r i s d r a w n , a c o n t i n u o u s s t r e a m o f i n f e r r e d p e n d i r e c t i o n i n f o r m a t i o n i s g e n e r a t e d . E x a c t l y how the d i r e c t i o n - c o d e s e q u e n c e i s r e c o g n i z e d as b e l o n g i n g t o one o f t h e p r e - d e f i n e d c l a s s e s i s t h e p o i n t o f d i s c u s s i o n f o r t h i s s e c t i o n . The d i c t i o n a r y ' s s t r u c t u r e i s r e p r e s e n t a b l e by a m o d i f i e d t r e e 40 s t r u c t u r e i n w h i c h e a c h node i s s u c c e e d e d by a maximum o f s i x o t h e r n o d e s . The nodes a r e l o g i c a l l y c o n n e c t e d by d i r e c t i o n c o d e s . I t i s u s e f u l t o v i s u a l i z e a node p o i n t e r w h i c h , as d i r e c t i o n codes a r e p a s s e d f r o m t h e f e a t u r e e x t r a c t i o n s t a g e , i s g u i d e d t h r o u g h t h e t r e e u n t i l a f a i r l y p o s i t i v e i d e n t i f i c a t i o n o f t h e unknown samp le may be o b t a i n e d . A p o r t i o n o f t r e e f o r ANSI n u m e r i c s i s i l l u s t r a t e d i n F i g . 3 . 9 . H o r i z o n t a l b a r s r e p r e s e n t t h e t op o f t h e node i n t h e l i n k e d - l i s t . V e r t i c a l l i n e s a r e node c o n n e c t o r s and a r e f o l l o w e d o n l y when t h e i r a s s o c i a t e d d i r e c t i o n codes a r e r e p o r t e d . N u m e r i c s i n c i r c l e s r e p r e s e n t t h e c l a s s i f i c a t i o n d e c i s i o n . I t i s i m p o r t a n t t o r e a l i z e t h a t a d i r e c t i o n - c o d e v e c t o r d e f i n e d f o r one c h a r a c t e r may be a s u b s e t o f t h a t d e f i n e d f o r a n o t h e r . Assume t h e s u b s e t v e c t o r i s i n p u t i n t h e u s u a l f a s h i o n and t h e p e n i s s u b s e q u e n t l y r a i s e d f r o m t h e p a p e r . I f n o f u r t h e r f o r c e d a t a a r e d e t e c t e d , t h e c l a s s i f i e r o u t p u t s t h e s y m b o l c o r r e s p o n d i n g t o t h e s u b s e t c h a r a c t e r . I f s u b s e q u e n t d i r e c t i o n i n f o r m a t i o n i s r e c e i v e d , t h e p o i n t e r moves e l s e w h e r e and i t i s p r o b a b l e t h a t t h e s u b s e t c h a r a c t e r was n o t i n t e n d e d . The d e c i s i o n , t h e r e -f o r e , i s b a s e d upon w h e t h e r o r n o t new d i r e c t i o n e o d e s a r e o b t a i n e d . The maximum w a i t i n g t i m e , t e r m e d t h e t i m e - o u t d e l a y , b o u n d s t h e p e r i o d d u r i n g w h i c h m e a n i n g f u l d a t a must be d e t e c t e d i n o r d e r t o f u r t h e r d i s p l a c e the p o i n t e r . I f d a t a i s n o t r e c e i v e d a c l a s s i f i c a t i o n d e c i s i o n r e f l e c t i n g t h e s u b s e t c h a r a c t e r i s o u t p u t . I n the t r e e d i a g r a m t h e s u b s e t c h a r a c t e r i s l o c a t e d a t t he b a s e o f t h e t i m e - o u t l i n k . I n F i g . 3 . 9 , t he p o i n t e r i s i n i t i a l l y s e t t o " S T A R T " . Suppose t h e u s e r t a k e s t h e p e n and b e g i n s t o w r i t e i n a "down" d i r e c t i o n ; t h e p o i n t e r i s m o d i f i e d a c c o r d i n g l y and r e m a i n s a t NODE B u n t i l a d i r e c t i o n o t h e r t h a n down Node A Node B d o w n p e n o f f WNode D d o w n P e n o f M Node C I e f t WNode E Node F 9 h Node G pen off 9 h u P F i g u r e 3 . 9 E x a m p l e o f t h e C l a s s i f i c a t i o n T r e e S t r u c t u r e . 42 i s r e p o r t e d . I f t h e p e n i s l i f t e d f r o m t h e p a p e r , t h e p o i n t e r i s u p d a t e d t o r e f e r e n c e an o u t p u t c i r c l e and d i g i t one i s t r a n s m i t t e d t o t h e w r i t e r f o r f e e d b a c k p u r p o s e s . D i r e c t i o n s o t h e r t h a n " D " w i l l n o t a f f e c t t h e p o i n t e r ' s p o s i t i o n ; t h e y a r e c o n s i d e r e d r e d u n d a n t t o t h e c l a s s i f i c a t i o n p r o c e s s s i n c e t h e r e s u l t i n g d i r e c t i o n - c o d e v e c t o r w o u l d n o t be a v a l i d member o f t h e n o m i n a l c h a r a c t e r r e p e r t o i r e . The f i r s t r i g h t s t r o k e u p d a t e s t h e p o i n t e r t o NODE C and a s u b s e q u e n t p e n - o f f code to NODE D . A t t h i s p o i n t a s o f t w a r e t i m e c o u n t e r i s s t a r t e d . S a m p l i n g c o n t i n u e s u n i n t e r r u p t e d and u n l e s s a downward s t r o k e i s i n f e r r e d , t h e s y s t e m " t i m e s - o u t " , d i g i t one i s communica t ed t o t h e w r i t e r and t h e p o i n t e r i s r e p o s i t i o n e d t o t h e top o f t h e d a t a s t r u c t u r e . N o t i c e t h a t " D R O " , a s w e l l a s t h e n o m i n a l " D O " , i s c o n s i d e r e d r e p r e s e n t i t i v e o f h a n d p r i n t e d n u m e r i c o n e . T o l e r a n c e to t h e f i n a l " R " u n d e r l i n e s a n o t h e r c h a r a c t e r i s t i c o f t h e d i c t i o n a r y ; i t i s e x p l a i n e d n e x t . A l t h o u g h t h e w r i t e r i s c a u t i o n e d a g a i n s t a l l o w i n g t h e p e n - t i p t o c o n t a c t t he w r i t i n g medium b e f o r e and a f t e r i n t e n d e d s t r o k e s a r e f o r m e d , s p u r i o u s d a t a a r e i n v a r i a b l y g e n e r a t e d a s a c o n s e q u e n c e o f t h e s t r a i n - g a u g e a r r a y ' s h i g h s e n s i t i v i t y . A l a r g e p e r c e n t a g e o f t h e s e u n i n t e n t i o n a l ; v a r i a t i o n s a r e d i s c a r d e d d u r i n g f r o n t - e n d p r e - p r o c e s s i n g b u t o c c a s i o n a l l y n o t a l l a r e e l i m i n a t e d . The d i c t i o n a r y p r o v i d e s a s e c o n d d e g r e e o f s a f e t y and i n t h e c a s e o f d i g i t o n e , "DRO" i s a c c e p t e d as an a l l o w e d v a r i a n t and s p u r i o u s d a t a " R " i s deemed i r r e l e v a n t t o t h e c l a s s i f i c a t i o n p r o c e s s . A s i m i l a r e x a m p l e a p p e a r s as P l a t e (B) i n F i g . 3 . 1 0 where s p u r i o u s d a t a " R U " a r e g e n e r a t e d a t t h e b a s e o f t h e h a n d p r i n t e d " 9 " . The d e c i s i o n s t r u c t u r e i s u n a f f e c t e d and a c o r r e c t r e c o g n i t i o n d e c i s i o n i s r e p o r t e d . SLOPE? CODE VECTOR} UROLROLO OF CHARACTER J P L A T E (A) I n t e n t i o n a l S t r o k e F o r m a t i o n (URDLRDLO) P L A T E (B) U n i t e n t i o n a l S p u r i o u s D a t a (LDRUDRUO) F i g u r e 3 . 1 0 E x a m p l e s o f S t r o k e E n d - P o i n t D a t a E v e n i n t e n t i o n a l s t r o k e s a r e somet imes c l a s s i f i e d as i r r e l e v a n t . A n o m i n a l d i g i t t h r e e i s begun w i t h a r i g h t w a r d s t r o k e b u t P l a t e (A) o f F i g . 3 . 1 0 d e p i c t s an upward s t r o k e . N o t i c e how t h e u s e r i s n o t p e n a l i z e d ; v a r i a t i o n s a r e t o l e r a t e d u n t i l t h e y b e g i n t o i n f l u e n c e the c l a s s i f i c a t i o n p e r f o r m a n c e o f o t h e r members o f t h e d e f i n e d c h a r a c t e r s e t . I n o r d e r t o f u r t h e r d e c r e a s e s y s t e m r e s p o n s e t i m e i t i s assumed t h a t a l l i n p u t r e p r e s e n t h o n e s t a t t e m p t s a t f o r m i n g c h a r a c t e r s o f t h e d e f i n e d s y m b o l - s e t . I t i s u n d e r s t o o d , f o r e x a m p l e , t h a t w r i t e r s w i l l n o t e n t e r l e t t e r s when w o r k i n g w i t h a n u m e r i c s o n l y d i c t i o n a r y . C o n s e q u e n t l y , c h a r a c t e r s c a n o f t e n be c o r r e c t l y r e c o g n i z e d b e f o r e t h e u s e r h a s f i n i s h e d f o r m i n g them; enough i n f o r m a t i o n h a d a l r e a d y b e e n r e c e i v e d t o e x c l u d e t h e p o s s i b i l i t y o f a l l o t h e r s y m b o l - s e t members . T h i s i d e a i s i l l u s t r a t e d i n t h e t r u n c a t e d s t r u c t u r e o f F i g . 3 . 1 1 . An example o f t h e d i c t i o n a r y ' s i n h e r e n t t o l e r a n c e t o n o n - n o m i n a l c h a r a c t e r fo rms a p p e a r s i n F i g . 3 . 1 2 . A d e c i s i o n t r e e f o r t h e 2 - s t r o k e d i g i t f i v e i s i n d i c a t e d . A s t h e w r i t e r f o rms the f i r s t s t r o k e , " b " } t h e p o i n t e r moves t h r o u g h t h e t r e e f r o m " S T A R T " t o n o d e . E . To c o m p l e t e t he c h a r a c t e r , t h e u s e r l i f t s t h e p e n and makes t h e n e c e s s a r y r i g h t g o i n g s t r o k e . Upon o b s e r v i n g raw d a t a , i t became e v i d e n t t h a t o n l y the e x p e r i e n c e d u s e r c o u l d f o r m the s e c o n d s t r o k e , a s i m p l e " R O " , c o r r e c t l y . M o s t u s e r s u n i n t e n t i o n a l l y p r o d u c e d some f o r m o f s p u r i o u s e n d - p o i n t d a t a . D i r e c t i o n - c o d e v e c t o r s s u c h a s " U R U O " , " U R D O " , and " L U R O " were common. The r e c o g n i t i o n l o g i c f o l l o w i n g node E accomoda te s a l l s u c h c o m b i n a t i o n s . N o t e t h a t i f a p a r t i c u l a r d i r e c t i o n l i n k does n o t i s s u e f r o m a n o d e , t h e p o i n t e r i s n o t u p d a t e d when s u c h a d i r e c t i o n i s r e g i s t e r e d . 45 Star t '0 'D 0 0' R Example (A) F u l l Recognition Logic "0 R 0 R' '0 Example (B) Truncated Recognition Logic. A C l a s s i f i c a t i o n Decision i s Rendered Before the Symbol i s Completed by the User. Figure 3.11 An I l l u s t r a t i o n of Inherent Dictionary  Compactness. (Logic for Special Character , RODORORO.) Node A W D W Node B R W Node C D W Node P L Node E P Node F Figure 3.12 A Demonstration of the  Dictionary's Tolerance  to Symbol Variations (Numeric,"5"). R VNode G Legend: D=down l;= left P- pen-off H'= r ight By not having to specifically provide for a l l possible variations the dictionary structure tends to be compact and readable. Since valuable time i s not wasted updating the node pointer in the case of irrelevant data system response time i s very low. Once the system designer has decided upon a symbol-set and any variations that should be tolerated, a tree i s drawn and the l i n k e d - l i s t constructed. The design of a standard numerics dictionary requires approxi mately 5 man-hours. Modifications can usually be effected in a matter of minutes. Data structure formatting of the linked-list i s f a i r l y arbitrary. Before some experience with tree construction had been gained, a 16-bit word per node entry was u t i l i z e d . This allowed pointer updates from and to anywhere within the l i s t . Later, an 8-bit per entry format which limited jumps to 63 entries was adopted. Even extensive dictionaries can be constructed under this constraint. There are six sequential entries per node and nodes may be entered in any order. Two of the formats used are i l l u s t r a t e d in Fig. 3.13 3.5 Testing at Intermediate Stages 3.5.1 Spurious Data at Stroke End-Points In Section 3.3 .2, i t was indicated that pen-tip position i s not readily extracted from force information. Precise character forms cannot be reconstructed yet approximate shapes adequate for diagnostic purposes may be derived with the use of a graphics display system. If pen-tip pressure is .assumed directly proportional to cursor velocity, processed force data may be applied to determine display coor-dinate increments. This data may then be used to drive a displayed trace 48 (A) L i s t Structure node ( i -1} node ( i ) node { (B) Preferred Format for 8-bit, Microcomputer - 1 Byte per L i s t Entry entry (k) entry (k+1) ?able Jump Flag Sign-Bit for +63 Table Jump (C) Alte r n a t i v e Format ; One 16-bit Word Per L i s t Entry e n t r y (k) e n t r y (k+1) sign/type f l a g meaning 00 01 10 Po s i t i v e or Zero Jump Negative Jump A s c i i Flag F i g u r e 3.13 L i n k e d - L i s t E n t r y F o r m a t t i n g 49 c u r s o r . F i g . 3 . 7 i l l u s t r a t e s s e v e r a l c a l c u l a t e d s y m b o l t r a c e s . S p u r i o u s e n d - p o i n t d a t a a r e w e l l r e p r e s e n t e d ; t h e i r s l o w e r movements g e n e r a t e many d a t a p o i n t s . W i t h t h e a i d o f t h e d e s c r i b e d d i s p l a y s y s t e m u s e r s were a b l e t o i d e n t i f y and c o r r e c t c h r o n i c d i f f i c u l t i e s w h i c h o f t e n stemmed f r o m p o o r p e n p o s t u r e and vague s t r o k e d e f i n i t i o n . 3 . 5 . 2 D i r e c t i o n - C o d e V e c t o r C a l c u l a t i o n f o r S y s t e m ' a r a m e t e r and D i c t i o n a r y  e n t r y O p t i m i z a t i o n B e f o r e d e s i g n i n g t h e r e c o g n i t i o n l o g i c , p r e - p r o c e s s i n g and f e a t u r e e x t r a c t i o n t e c h n i q u e s w e r e t e s t e d r i g o u r o u s l y . A p p r o x i m a t e l y 15 s u b j e c t s w e r e i n v o l v e d a t t h i s l e v e l o f t e s t i n g . V a r i o u s c h a r a c t e r s e t s w e r e s e l e c t e d w i t h s p e c i a l e m p h a s i s p l a c e d on t h e d i g i t s z e r o t h r o u g h n i n e . T h i s f o r m o f i n t e r m e d i a t e t e s t i n g was f r u i t f u l i n i d e n t i f y i n g p a r a m e t e r r a n g e s u s e d l a t e r i n d i c t i o n a r y p e r s o n a l i z a t i o n e x p e r i m e n t s ( S e c t i o n 4 . 2 ) . The d i a g n o s t i c p r o g r a m was a l s o i n v o l v e d i n t h e c o n s t r u c t i o n o f t h e d i c t i o n a r y u s e d i n t h e f i n a l s t a g e o f t h e p r o p o s e d s y s t e m . S u b j e c t s w e r e r e q u e s t e d t o t r y t o i m p r o v e t h e i r r e c o g n i t i o n s c o r e s ; t h e c h a r a c t e r t r a c e p r o v i d e d s t r o n g p o s i t i v e r e i n f o r c e m e n t f o r w e l l - d r a w n f o r m s . C o n -c u r r e n t l y , t h e g e n e r a t e d d i r e c t i o n - c o d e v e c t o r s w e r e t a b u l a t e d and s t o r e d , f o r f u t u r e r e f e r e n c e . A s u b s e q u e n t e x a m i n a t i o n i n f l u e n c e d t h e f i n a l s e l e c t -i o n o f d i c t i o n a r y p r o t o t y p e s and h e l p e d d e f i n e w h i c h c h a r a c t e r v a r i a t i o n s w e r e most common. I n the n e x t s e c t i o n s e v e r a l o t h e r t e c h n i q u e s a p p l i e d t o i m p r o v e u s e r s ' p e r f o r m a n c e a r e d e s c r i b e d . 50 3 . 5 . 3 D e v e l o p m e n t o f U s e r - T r a i n i n g A i d s S i n c e a d i s p l a y p r o c e s s o r w o u l d p r o b a b l y n o t be a v a i l a b l e i n a n o n - l a b o r a t o r y i m p l e m e n t a t i o n an a l t e r n a t e d i a g n o s t i c t o o l was d e v i s e d . F o u r LED i n d i c a t o r s w e r e mounted on the h a r d w a r e i n t e r f a c e modu le and c o n f i g u r e d t o m o n i t o r and d i s p l a y i n s t a n t a n e o u s q u a n t i z e d p e n d i r e c t i o n . A p h o t o g r a p h o f t h e pen and s u p p o r t i n g h a r d w a r e s h o w i n g t h e L E D ' s a r r a n g e d i n t h e u n i f o r m q u a d r a n t c o n f i g u r a t i o n d e s c r i b e d e a r l i e r i s shown, i n A p p e n d i x C . P o o r r e c o g n i t i o n o f t e n r e s u l t e d f r o m t h e u s e r f o r g e t t i n g t o k e e p t h e p e n t i p p e r p e n d i c u l a r t o t h e w r i t i n g med ium. The i n d i c a t o r s w e r e u s e f u l i n d e t e c t i n g t h i s c o n d i t i o n . W i t h t h e p e n l e a n i n g t o w a r d s t h e l e f t t h e s t r a i n - g a u g e s w o u l d i n f e r l e f t d i r e c t i o n s i g n a l s t o t h e LED a r r a y even, i f t h e p e n was m o v i n g t o t h e r i g h t . S i n c e t h i s p r o b l e m was r e c u r r e n t f o r some u s e r s , a s p e c i a l t r a i n i n g - a i d was d e v e l o p e d t o a l l e v i a t e and e v e n t u a l l y e l i m i n a t e t h e d i f f i c u l t y . T w o - p o i n t m e t a l s u p p o r t f rames t h a t h e l d the p e n f i r m l y and i n a n o m i n a l l y v e r t i c a l a t t i t u d e were made a v a i l a b l e t o t h e u s e r s . The p e n - t i p and t h e l e g s o f t h e frame d e f i n e v e r t i c e s o f a t r i a n g l e i n , t h e p l a n e o f t h e p a p e r . W i t h o u t e x c e p t i o n s y s t e m p e r f o r m a n c e i m p r o v e d s i g n i f i c a n t l y upon i n t r o d u c i n g t h e new d e v i c e . The s u p p o r t was r e m o v e d , h o w e v e r , a s s o o n as t h e u s e r h a d g a i n e d some e x p e r i e n c e i n w r i t i n g s i n c e i t s u se was c o n t r a r y t o p r i o r c l a i m s o f a n a t u r a l d e v i c e . S u b j e c t s were a s k e d t o t a k e n o t e o f how t h e pen f i t t e d t h e hand when c o r r e c t l y s u p p o r t e d . S u g g e s t i o n s r e g a r d i n g p e n - b a r r e l r e p o s i t i o n i n g and r e s h a p i u g were s o l i c i t e d . Comments r e c e i v e d w e r e n o t e d and a r e s u m m a r i z e d i n C h a p t e r V . S i n c e a t t h i s p o i n t t h e m a i n c o n c e r n was e v a l u a t i n g t h e d e f i n e d s y s t e m , no a t t e m p t was made t o m o d i f y p e n h a r d w a r e . 51 I V . F I N A L EVALUATION OF THE COMPLETED RECOGNITION SYSTEM 4 . 1 C l a s s i f i c a t i o n w i t h a R e s t r i c t e d D i c t i o n a r y E x p e r i m e n t s r e l a t i n g t o t h e d e s i g n o b j e c t i v e s o u t l i n e d i n T a b l e I were p e r f o r m e d on t h e c o m p l e t e d s y s t e m . A l t h o u g h a number o f o b j e c t i v e s r e q u i r e d l i t t l e o r n o t e s t i n g f o r t h e i r e v a l u a t i o n , o t h e r s n e c e s s i t a t e d a t h o r o u g h i n v e s t i g a t i o n . I t was c o n s i d e r e d i m p o r t a n t t o p e r f o r m r e p e t i t i v e t r i a l s , t o d e f i n e c o n t r o l g r o u p s , and t o t e s t i n an e n v i r o n m e n t i n w h i c h t h o s e f a c t o r s n o t u n d e r a n a l y s i s c o u l d be h e l d c o n s t a n t . Any r e s u l t s o b t a i n e d w e r e r e g a r d e d as s t a t i s t i c a l i n n a t u r e and a s s u c h s u b j e c t t o m i s i n t e r p r e t a t i o n . S p e c i a l c a r e was t a k e n t o a p p l y t h e c o r r e c t me thod o f s t a t i s t i c a l a n a l y s i s t o e a c h d a t a s e t . A s i d e f r o m t h e s y s t e m c h a r a c t e r i s t i c s t a b u l a t e d i n C h a p t e r I , t h e r e a r e a number o f g e n e r a l r e c o g n i t i o n scheme p a r a m e t e r s t h a t had t o be c o n s i d e r e d . E x p e r i m e n t i n g w i t h t h e A m e r i c a n N a t i o n a l S t a n d a r d s I n s t i t u t e ( A N S I ) p r o p o s e d c h a r a c t e r s e t f o r h a n d p r i n t i n g f a c i l i t a t e d c o m p a r i s o n w i t h o t h e r c l a s s i f i c a t i o n s c h e m e s . An e x a m p l e o f a c o m p l e t e d s c o r i n g s h e e t a p p e a r s as F i g . 4 . 1 . E a c h s u b j e c t i s i d e n t i f i e d and c a t e g o r i z e d a s b e l o n g i n g t o one o f t h r e e g r o u p s . R e s u l t s o f f o u r s e s s i o n s , e a c h c o m p r i s i n g 3 3n a s m a l l ( l e s s t h a n —") and a l a r g e ( g r e a t e r t h a n — ) s e t o f h a n d p r i n t e d o o A N S I . d i g i t s , w e r e r e c o r d e d . A t o t a l o f s e v e n e x p e r i m e n t s w e r e c o n d u c t e d on t w e n t y i n d i v i d u a l s and more t h a n f o u r t h o u s a n d d i g i t s were p r o c e s s e d . A r e d u c t i o n i n s a m p l e number w o u l d have r e n d e r e d r e s u l t s l e s s m e a n i n g f u l (and p e r h a p s e v e n s t a t i s t i c a l l y i n s i g n i f i c a n t ) b e c a u s e o f t h e h i g h s a m p l e v a r i a n c e e n c o u n t e r e d . G E N E R A L D I C T I O N A R Y * T E S T I N G C O N S T R A I N T S P L A C E D U P O N T H E U S E R | W r i t i n g S p e e d : h o n e W r i t i n g M e d i u m : n o n e S t y l i s t i c : a ) A N S I c o n f o r m i n g b ) z e r o a s S S y s t e m T e s t P a r a m e t e r s X , Y - P r e s s u r e T h r e s h o l d : 6 T i m e - c u t v a l u e ( s e c . ) : 0 . 6 P l a n e Z - P r e s s u r e T h r e s h o l d : 6 C l i p p i n g T i m e ( s e c . ) : 0 . 0 8 N o n - l i n e a r i z a t i o n ( d e g ' s . ) : 0" S U B J E C T S U 3 J E C T C H A R A C T E R T E S T c E S S 1 0 N N U M B E R C A T E G O R Y I D E N T I F I E R S I Z E D I G I T 1 2 3 4 r w H U C M U C M U C M U P r o f e s s i o n a l / T e c h n i c a l i S u b j e c t VI S M A L L z e r o o n e t w o t h r e e f o u r f i v e s i x s e v e n e i g h t n i n e X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X S u b - T o t a l £ 6 . 4 0 8 2 0 9 1 0 1 0 0 0 1 L A R G E z e r o o n e t w o t h r e e f o u r f i v e s i x s e v e n e i g h t n i n e X X X X X X X X X X X X X X X X X X X x X X X X X X X X X X X X X X X X X X X X S u b - T o t a l s 8 2 0 9 1 0 8 2 0 9 1 0 L A R G E S S H A L L T O T A L S 1 4 6 0 1 7 3 0 1 7 3 0 1 9 1 0 L e g e n d : C - c l a s s i f i e d c o r r e c t l y M * r n i s c l a s s i f i c d * c o n f o r m i n g t o A N S I s t a n d a r d s f o r h a n d p r i n t e d c h a r a c t e r s U • u n k n o w n t o t h e d i c t i o n a r y Figure 4.1 Example of a Completed Recognition Performance Scoring Sheet 53 , The s e v e n q u e s t i o n s f o r w h i c h answers w e r e sought: a r e : i ) Does s y s t e m r e c o g n i t i o n p e r f o r m a n c e f o r most u s e r s p r o g r e s s i n some p r e d i c t a b l e manner? Does t h e s y s t e m d i c t a t e the c l a s s i c a l e x p o n e n t i a l l e a r n i n g c u r v e ? i i ) I s r e c o g n i t i o n p e r f o r m a n c e d i r e c t l y r e l a t e d t o t h e t y p e o f u s e r o p e r a t i n g t h e sys t em? i . e . , a r e i n t e r -u s e r - c a t e g o r y d i f f e r e n c e s s i g n i f i c a n t ? i i i ) I s p e r f o r m a n c e s e n s i t i v e t o c h a r a c t e r - s i z e v a r i a t i o n s ? i v ) Does t h e r i g h t - h a n d e d u s e r h a v e an a d v a n t a g e o v e r t h e l e f t - h a n d e d u s e r ? v) How much u s e r t r a i n i n g i s r e q u i r e d b e f o r e p e r f o r m a n c e a t t a i n s t he w i d e l y a c c e p t e d l e v e l o f 95%? v i ) Once a u s e r i s " t r a i n e d " , a r e m i s c l a s s i f i c a t i o n s l i m i t e d t o c e r t a i n c h a r a c t e r s ? How o f t e n does a n i n p u t g e n e r a t e t h e r e s p o n s e , "UNKNOWN"? v i i ) I s a c c e p t a b l e s y s t e m p e r f o r m a n c e c o n t i n g e n t upon c o n t i n u a l u s e r t r a i n i n g o r i s t h e s k i l l e a s i l y r e t a i n e d ? I n t h e pages t h a t f o l l o w , e x p e r i m e n t s p e r f o r m e d and r e s u l t s o b t a i n e d a r e d e s c r i b e d i n d e t a i l . 4 . 1 . 1 The L e a r n i n g C u r v e The f i r s t s e c t i o n o f s u b j e c t p e r f o r m a n c e e v a l u a t i o n i s c o n c e r n e d w i t h t h e f a m i l i a r i z a t i o n p r o c e s s . S u b j e c t s w e r e d i v i d e d i n t o t h r e e s p e c i f i c g r o u p s f o r t h e p u r p o s e o f i n v e s t i g a t i n g r e c o g n i t i o n p e r f o r m a n c e dependence upon u s e r t y p e ( i . e . , p r o f e s s i o n a l / t e c h n i c a l , p r o f e s s i o n a l / n o n - t e c h n i c a l , and n o n - p r o f e s s i o n a l / n o n - t e c h n i c a l ) . T h r o u g h o u t t e s t i n g s u b j e c t s w e r e a s k e d t o a d h e r e t o ANSI c h a r a c t e r fo rms w i t h t h e e x c e p t i o n o f d i g i t z e r o w h i c h was t o be w r i t t e n as an o e r s t e d (0). O f p a r t i c u l a r i n t e r e s t was t h e l e a r n i n g c u r v e f o l l o w e d b y e a c h o f t h e s u b j e c t c a t e g o r i e s . I t was found t h a t t h e f a m i l i a r i z a t i o n p e r i o d c o u l d be k e p t f a i r l y b r i e f and t h a t n o n - t e c h n i c a l u s e r s f u n c t i o n e d as w e l l a s t e c h n i c a l u s e r s . The a v e r a g e r e c o g n i t i o n p e r f o r m a n c e f o r e a c h t r i a l i n e a c h s u b j e c t c a t e g o r y i s shown i n T a b l e I I I . F i g . 4 . 2 i s a g r a p h i c a l r e p r e s e n t a t i o n , o f t h i s d a t a . TABLE I I I AVERAGE RECOGNITION PERFORMANCE S U B J E C T / CATEGORY AVERAGE RECOGNITION PERFORMANCE (%) T R I A L 1 T R I A L 2 T R I A L 3 T R I A L 4 P r o f . / T e c h . 5 6 . 0 7 3 . 1 7 9 . 1 8 8 . 1 P r o f . / N o n - T e c h . 3 9 . 2 6 4 . 2 7 5 . 8 9 0 . 0 N o n - P r o f . / N o n - T e c h . 4 3 . 8 6 0 . 0 7 6 . 3 8 7 . 5 WEIGHTED AVERAGE 5 0 . 2 6 9 . 1 7 7 . 9 8 8 . 5 NO TRAINING 5 M I N . OF TRAINING 10 M I N . OF TRAINING 15 M I N . OF TRAINING I t i s c l e a r f r o m t h e p o o r r e s u l t s o f t r i a l 1 t h a t t h e s y s t e m c a n n o t be e x p e c t e d t o p e r f o r m a d e q u a t e l y w i t h o u t some u s e r t r a i n i n g . ' n o n - t e c h n i c a l ' i s t o mean t h o s e s u b j e c t s who do n o t p o s s e s s d e t a i l e d k n o w l e d g e o f how t e c h n i c a l d e v i c e s o p e r a t e 20 18 -16 -• 12}-10 •• A Learning Curve i s Merely the Smooth Function Drawn Through the Points Representing Average Recognition Performance for Each Successive T r i a l Technical Trial 1 X Trial 2 Non-Technical (A Single Curve Represents Data Drawn from Performance Scores of Both Professional and Non-Professional Subjects) \ Professional/Tech. O Professional/Non-Tech. X Non-Prof./Non-Tech, 100 90 . .80 -70 -60 •50 •L0 •30 •20 ••10 Trial 3 Tr ia l U 5 10 lotal time spent in training (mins.) Figure 4.2 A Learning Curve of Single T r i a l Recognition Performance 15 As e x p e c t e d , t h e s u b j e c t ' s p e r f o r m a n c e i m p r o v e s w i t h p r a c t i c e , t h e a v e r a g e r e c o g n i t i o n p e r f o r m a n c e r o s e f r o m 50 t o 88% o v e r t h e i n i t i a l 1 5 - m i n u t e p e r i o d . Improvement does n o t , h o w e v e r , c o n f o r m e x a c t l y t o t h e c l a s s i c a l e x p o n e n t i a l f u n c t i o n s i n c e u s e r s a r e n o t l e a r n i n g a new s k i l l . A f t e r 15 m i n u t e s o f t r a i n i n g , s u b j e c t s w e r e a v e r a g i n g s l i g h t l y l e s s t h a n 90% r e c o g n i t i o n . I n t h e l i t e r a t u r e a 95% minimum p e r f o r m a n c e i s u s u a l l y r e q u e s t e d f o r a r e a l - t i m e h a n d p r i n t e d c h a r a c t e r r e c o g n i t i o n scheme [ C H U I 7 6 ] . S e c t i o n 4 . 1 . 5 o f t h i s t h e s i s i s d e v o t e d to d e t e r n u n i n g t h e t i m e r e q u i r e d t o a c h i e v e t h i s p e r f o r m a n c e l e v e l . A l t h o u g h t h e p r o f e s s i o n a l / t e c h n i c a l s u b j e c t a c h i e v e s t h e bes t : p e r f o r m a n c e i n the " n o - u s e r t r a i n i n g " s e s s i o n ( 5 6 . 0 v e r s u s 3 9 . 2 and 4 3 . 8 % ) , h i s t o t a l i m p r o v e m e n t i s l e s s t h a n t h a t f o r each o f t h e o t h e r c a t e g o r i e s and h i s f i n a l p e r f o r m a n c e a f t e r 15 m i n u t e s o f t r a i n i n g i s n o t g r e a t e r t h a n the a v e r a g e s u b j e c t ' s p e r f o r m a n c e ( 8 8 . 1 v e r s u s 8 8 . 5 ) . Sample r e s u l t s i n f e r t h a t a l t h o u g h c e r t a i n u s e r s may h a v e an i n i t i a l a d v a n t a g e , a l l u s e r s p e r f o r m e q u a l l y w e l l a f t e r a b r i e f t r a i n i n g p e r i o d . I n p a r t i c u l a r , t h e n o n - p r o f e s s i o n a l / n o n - t e c h n i c a l s u b j e c t does n o t a p p e a r t o s u f f e r any h a n d i c a p s . A s y s t e m d e s i g n g o a l seems t o h a v e b e e n m e t , t he e n v i r o n m e n t / i n t e r f a c e r e f l e c t s t h e n a t u r a l t e n d e n c i e s o f t h e n o n -t e c h n i c a l u s e r . A more r i g o r o u s p e r f o r m a n c e a n a l y s i s i s u n d e r t a k e n i n t h e n e x t s e c t i o n . 4 . 1 . 2 P e r f o r m a n c e S e n s i t i v i t y t o U s e r C a t e g o r y The p u r p o s e o f t h i s s e c t i o n i s t o compare r e c o g n i t i o n scheme ; p e r f o r m a n c e f o r u s e r s f r o m e a c h c a t e g o r y once t h e y a r e f a m i l i a r w i t h t h e 57 s y s t e m ' s o p e r a t i o n . I n p a r t i c u l a r , t h e h y p o t h e s i s t h a t p e r f o r m a n c e a f t e r 15 m i n u t e s o f t e s t i n g i s i n d e p e n d e n t o f s u b j e c t c a t e g o r y w i l l be s t a t i s t i c a l l y a n a l y z e d . R e c o g n i t i o n s c o r e s f o r e a c h o f t h e t h r e e c a t e g o r i e s a p p e a r i n T a b l e I V . TABLE I V PERFORMANCE AFTER 15 MINUTES OF TRAINING CATEGORY/ SUBJECT SUBJECT PERFORMANCE FOLLOWING 15 MINUTES OF TRAINING (%) CATEGORY MEAN P E R F O R M -ANCE P r o f e s s i o n a l / T e c h n i c a l 95 95 95 95 75 85 80 90 95 85 90 95 80 85 80 90 88.1 P r o f e s s i o n a l / N o n - T e c h n i c a l 90 85 90 95 85 90 88.3 N o n - P r o f e s s i o n a l / N o n - T e c h n i c a l 85 90 85 90 87.5 S i n c e o b t a i n e d d a t a a r e i m p l i c i t l y i n f l u e n c e d by human j u d g e m e n t , p e r f o r m a n c e i s s u b j e c t t o c h a n c e f l u c t u a t i o n s . F o r e x a m p l e , s c o r e s r a n g i n g f r o m 75% t o 95% w e r e r e c o r d e d f o r p r o f e s s i o n a l / t e c h n i c a l s u b j e c t s . A r e a s o n a b l e s t a r t i n g p o i n t i s a c a l c u l a t i o n o f t h e d e g r e e t o w h i c h c a t e g o r y means d i f f e r . A s m a l l v a r i a n c e w o u l d s t r e n g t h e n t h e c l a i m f o r a c c e p t i n g t h e h y p o t h e s i s t h a t p e r f o r m a n c e i s i n d e p e n d e n t o f c a t e g o r y . 2 U n f o r t u n a t e l y t h e v a r i a n c e o f s a m p l e means ( s_ ) i n d i c a t e s n o t h i n g o f p e r f o r m a n c e v a r i a t i o n w i t h i n t h e c a t e g o r y and w i t h o u t f u r t h e r k n o w l e d g e o f 2 s u b j e c t p e r f o r m a n c e f l u c t u a t i o n s ( i . e . , s u b j e c t p e r f o r m a n c e v a r i a n c e , ) i t w o u l d be u n w i s e t o make any i n f e r e n c e s r e g a r d i n g u n d e r l y i n g p o p u l a t i o n p a r a m e t e r s . The n u l l h y p o t h e s i s must be i n t r o d u c e d a t t h i s t i m e . L e t A be a random v a r i a b l e t h a t d e s c r i b e s t h e d i f f e r e n c e b e t w e e n two o t h e r random v a r i a b l e s . L e t A x C A T > i n p a r t i c u l a r , r e p r e s e n t t h e d i f f e r e n c e i n mean c a t e g o r y s c o r e s . The c o n d i t i o n A x _ = 0 d e n o t e s t h e n u l l h y p o t h e s i s , t h e h y p o t h e s i s t h a t p e r f o r m a n c e i s n o t r e l a t e d t o s u b j e c t c a t e g o r y , i . e . , t h a t s a m p l e s w e r e drawn f r o m a s i n g l e s t a t i s t i c a l p o p u l a t i o n . 2 By d e f i n i n g t h e " p o o l e d s u b j e c t p e r f o r m a n c e v a r i a n c e " , ( s )•, as P 2 t h e a v e r a g e o f s u b j e c t p e r f o r m a n c e v a r i a n c e s (s ) , t h e q u e s t i o n o f c a t e g o r y 2 2 i n d e p e n d e n c e r e s o l v e s t o a c o m p a r i s o n o f and s^ . I f t he p o p u l a t i o n s 2 a r e d i f f e r e n t , i . e . , i f t he n u l l h y p o t h e s i s i s n o t a c c e p t a b l e , t h e n s_ 2 w o u l d be s i g n i f i c a n t l y l a r g e r t h a n S p • B e f o r e p e r f o r m i n g t h e n u m e r i c a l c a l c u l a t i o n s a f i n a l p o i n t needs 2 t o be r a i s e d . A c c o r d i n g t o the C e n t r a l L i m i t Theorem s_ i s e x p e c t e d t o be 2 s m a l l e r t h a n s^ by a f a c t o r o f n , the number o f s a m p l e s o b t a i n e d f r o m e a c h c a t e g o r y [ H O E L 6 2 ] . T h e r e f o r e , i f t h e r a t i o , 2 n s _ F = X 2 SP (4 ) commonly t e r m e d t h e v a r i a n c e r a t i o [WONN72] i s s i g n i f i c a n t l y l e s s t h a n 1, t h e n u l l h y p o t h e s i s c o u l d be s a f e l y a c c e p t e d . The v a r i a n c e r a t i o ' s p r o b a b i l i t y f u n c t i o n i s dependen t upon t h e d e g r e e s o f f r e e d o m o f F , ( r - 1 ) f o r t h e n u m e r a t o r and r ( n - l ) i n t h e d e n o m i n a t o r where r r e p r e s e n t s t h e number o f c a t e g o r i e s and n , t h e number o f s u b j e c t s w i t h i n e a c h c a t e g o r y . R i g o r o u s p r o o f s f o r d e g r e e s o f f r eedom f o r m u l a e may be f o u n d i n many f o r m a l s t a t i s t i c s t e x t s [ H O E L 6 2 ] . T a b l e ' V i s a s t a n d a r d A n a l y s i s o f V a r i a n c e (ANOVA) t a b l e m o d i f i e d f o r c a t e g o r i e s o f u n e q u a l s i z e [WONN72]. TABLE V ANOVA TABLE FOR USERS FROM DIFFERENT CATEGORIES - = 2 Z n. (x.-x) = 0.1102, i 1=1 1 = 1 + 0.5116, 1 = 2 + 0.1731, i = 3 = 0.7949 = SS r n i _ 2 I I ( x ± i - x ) i=l j=l 1 = 27.2 , 1 = 1 + 2.0 , i = 2 + 1.0 , i = 3 = 30.2 = SS u DEGREES OF FREEDOM r - 1 = 2 Z (n - 1) = 15 1=1 1 + 5 + __3 = 23 MSS = SS /(r - 1) r v K ' = 0.397 MSS = SS / £ (n. - 1) u u . , i i=l = 1.313 MSS F = MSS 0.3024 u ACCEPT THE HYPOTHESIS T h i s t e c h n i q u e i m p l i c i t l y assumes t h a t s amp le s a r e drawn f r o m 2 n o r m a l p o p u l a t i o n s w i t h t h e same v a r i a n c e , a . The p o p u l a t i o n means may o r may n o t be t h e same. I n d e e d , i t i s t h e i r p o s s i b l e d i f f e r e n c e s t h a t a r e b e i n g i n v e s t i g a t e d t h r o u g h ANOVA t e s t i n g . The r a t i o , F , e v a l u a t e s t o 0 . 3 0 2 4 and t h e r e f o r e t h e o b s e r v e d d i f f e r e n c e i n c a t e g o r y means i s e a s i l y e x p l a i n e d by chance f l u c t u a t i o n s . E x p r e s s i n g t h e s e r e s u l t s i n a more f o r m a l manne r , t h e h y p o t h e s i s t h a t r e c o g n i t i o n p e r f o r m a n c e a f t e r 15 m i n u t e s o f t r a i n i n g i s n o t d e p e n d e n t upon u s e r t y p e i s c l e a r l y a c c e p t a b l e a t the c l a s s i c a l 5% s i g n i f i c a n c e l e v e l . 4 . 1 . 3 E f f e c t o f C h a r a c t e r S i z e on P e r f o r m a n c e , A number o f s u b j e c t s f e l t t h a t l a r g e r c h a r a c t e r s w e r e more e a s i l y d rawn t h a n s m a l l ones and t h a t r e c o g n i t i o n p e r f o r m a n c e w o u l d , as a r e s u l t , 3 be s u p e r i o r . The h y p o t h e s i s t h a t l a r g e d i g i t s (drawn g r e a t e r t h a n —") a r e more o f t e n c o r r e c t l y r e c o g n i z e d t h a n s m a l l e r d i g i t s was t e s t e d . D u r i n g l e a r n i n g c u r v e i n v e s t i g a t i o n an e q u a l number o f l a r g e and s m a l l d i g i t s were drawn b y e a c h s u b j e c t . The above h y p o t h e s i s i s i n v e s t i g a t e d t h r o u g h a c o m p a r i s o n o f l a r g e and s m a l l d i g i t p e r f o r m a n c e means f o r t h i s d a t a . Such a method o f p a i r e d s a m p l i n g ( i . e . , u s i n g t h e same s u b j e c t i n b o t h t r i a l s ) i s d e s i r a b l e s i n c e s u b j e c t v a r i a t i o n s do n o t i n f l u e n c e t h e p r o p o s e d h y p o t h e s i s t e s t . B e c a u s e o f s a m p l e s i z e d e f i c i e n c y ( a p r a c t i c a l c o n s i d e r a t i o n ) and a l a c k o f i n f o r m a t i o n r e g a r d i n g t h e p o p u l a t i o n s t a n d a r d d e v i a t i o n , t h e G a u s s i a n d i s t r i b u t i o n i s r e p l a c e d by t h e s t u d e n t ' s t d i s t r i b u t i o n [WONN72]. The h y p o t h e s i s t h a t p e r f o r m a n c e i s n o t i n any way r e l a t e d t o c h a r a c t e r s i z e , i . e . , t h e n u l l h y p o t h e s i s , i s r e p r e s e n t e d by H . L e t t i n g A r e p r e s e n t t h e random v a r i a b l e d e s c r i b i n g t h e d i f f e r e n c e i n p e r f o r m a n c e f o r l a r g e and s m a l l d i g i t s , t he A=0 c o n d i t i o n r e s t a t e s t h e n u l l h y p o t h e s i s . S i n c e r e s u l t s i n d i c a t e s u p e r i o r p e r f o r m a n c e f o r l a r g e r d i g i t s , t h e o n e - s i d e d a l t e r n a t i v e h y p o t h e s i s , , p o s t u l a t i n g a A e x c e e d i n g z e r o , i s p r e f e r a b l e t o t h e A^O h y p o t h e s i s . - . . • S t a t i s t i c a l l y , the q u e s t i o n r e d u c e s t o w h e t h e r o r n o t i t . i s l i k e l y t h a t t h e o b s e r v e d r e s u l t s w o u l d a r i s e i f t h e n u l l h y p o t h e s i s w e r e t r u e . I n p a r t i c u l a r , i t w i l l be d e t e r m i n e d i f t h e p r o b a b i l i t y o f o b t a i n i n g t h e o b s e r v e d s amp le d i f f e r e n c e s , a s s u m i n g w e r e t r u e , e x c e e d s t h e g e n e r a l l y a c c e p t e d s i g n i f i c a n c e v a l u e o f 5%. C a l c u l a t i o n s a r e p e r f o r m e d on a v e r a g e r e c o g n i t i o n s c o r e s d u r i n g t r a i n i n g s e s s i o n s 1 t o 3 and a g a i n on o b s e r v e d p e r f o r m a n c e d u r i n g s e s s i o n 4 i n an a t t e m p t t o u n c o v e r p o t e n t i a l e f f e c t s o f u s e r t r a i n i n g o n c l a s s i f i c a -t i o n p e r f o r m a n c e as r e l a t e d t o d i g i t s i z e . The c o r r e s p o n d i n g o n e - s i d e d c o n f i d e n c e r e l a t i o n i s , A > D - t ^ • ° 5 ^ ( 5 ) where ' D = a v e r a g e d i f f e r e n c e i n s amp le means t ^ = 5Z p r o b a b i l i t y l e v e l f o r , t h e S t u d e n t ' s t d i s t r i b u t i o n on n - 1 d e g r e e s o f f r e e d o m Sp = s t a n d a r d d e v i a t i o n o f s amp le d i f f e r e n c e s n = number o f s amp le s o b t a i n e d T a b l e V I s u m m a r i z e s c a l c u l a t i o n s o f l a r g e and s m a l l d i g i t p e r f o r m a n c e f o r e a c h c a t e g o r y . E q u a t i o n (5) i s e v a l u a t e d on t h e b a s i s o f d a t a o b t a i n e d and a p p l i e d t o c l a s s i c a l a c c e p t / r e j e c t h y p o t h e s i s t e s t i n g as i n d i c a t e d i n T a b l e V I I . R e s u l t s a r e s t a t i s t i c a l l y c o n c l u s i v e : t h e n u l l h y p o t h e s i s w h i c h i n d i c a t e s t h a t s y s t e m p e r f o r m a n c e i s i n d e p e n d e n t o f 62 c h a r a c t e r s i z e , i s r e j e c t e d d u r i n g the i n i t i a l p e r i o d o f s y s t e m f a m i l i a r i z a t i o n f o r a l l s u b j e c t c a t e g o r i e s . H o w e v e r , t h e n u l l h y p o t h e s i s i s a c c e p t e d a f t e r t h e u s e r h a s c o m p l e t e d the i n i t i a l 15 m i n u t e t r a i n i n g p e r i o d . Once a g a i n , c a t e g o r y dependence i s n o t i m p l i e d f u r t h e r s u b s t a n t i a t i n g t h e r e s u l t s o f e x p e r i m e n t a t i o n r e p o r t e d i n S e c t i o n 4 . 1 . 2 . TABLE V I MEAN AND VARIANCE OF DIFFERENCE DATA S U B J E C T / CATEGORY AVERAGE OF SESSIONS 1 , 2 , 3 SESSION 4 D = AVERAGE # DIFFERENCE (%) s'A = VARIANCE OF THE DIFFERENCE D = AVERAGE DIFFERENCE (%) s2=VARIANCE OF THE DIFFERNCE P r o f e s s i o n a l / T e c h n i c a l 6 . 8 7 1 .43 2 . 5 0 0 . 8 7 P r o f e s s i o n a l / N o n - T e c h n i c a l 7 . 2 0 0 . 7 3 0 . 0 0 2 . 0 0 N o n - P r o f e s s i o n a l / N o n - T e c h n i c a l 6 . 6 0 0 0 . 0 0 0 . 6 6 DIFFERENCE = S m a l l D i g i t P e r f o r m a n c e S u b t r a c t e d f r o m L a r g e D i g i t P e r f o r m a n c e TABLE V I I C L A S S I C A L HYPOTHESIS TESTING S U B J E C T / CATEGORY AVERAGE OF SESSIONS 1 , 2 , 3 SEE 5SI0N 4 CONFIDENCE t RELATION DECISION , REGARDING H Q CONFIDENCE RELATION DECISION REGARDING Hn P r o f e s s i o n a l / T e c h n i c a l A > 0 . 1 6 REJECT A > - 1 . 5 9 ACCEPT P r o f e s s i o n a l / N o n - T e c h n i c a l A > 0 . 0 2 REJECT A > - 1 . 1 6 ACCEPT N o n - P r o f e s s i o n a l N o n - T e c h n i c a l A > 0 . 6 6 REJECT A > - 0 . 9 6 ACCEPT R e f e r t o E q u a t i o n (5 ) ^ A c c e p t o r R e j e c t a t the c l a s s i c a l 5% s i g n i f i c a n c e l e v e l 63 4 . 1 . 4 R i g h t - and L e f t - Handedness P e n - t i p p o s t u r e p l a y s a v i t a l r o l e i n s u c c e s s f u l c l a s s i f i c a t i o n p e r f o r m a n c e . L e f t - h a n d e d p e r s o n s o f t e n h o l d t h e i r p e n a t an. a n g l e d i f f e r e n t f r o m t h a t assumed by r i g h t - h a n d e d p e r s o n s . D u r i n g t e s t i n g , s e v e r a l l e f t -handed s u b j e c t s e x p e r i e n c e d d i f f i c u l t i e s w i t h t h e p e n and s u g g e s t e d t h a t t he n o r m a l w r i t i n g t e c h n i q u e f o r t h e Xebec pen i m p l i c i t l y f a v o r e d r i g h t -h a n d e d n e s s . A n e x a m i n a t i o n o f r e c o g n i t i o n s c o r e s d rawn f r o m i n d e p e n d e n t s a m p l e s o f b o t h t y p e s o f u s e r s was p e r f o r m e d i n o r d e r t o s t a t i s t i c a l l y s u b s t a n t i a t e o r c o n t r a d i c t t h e i r c l a i m . A l l l e f t - h a n d e d p a r t i c i p a n t s f e l l i n t o t h e p r o f e s s i o n a l / t e c h n i c a l c a t e g o r y ; t h i s does n o t r e d u c e t h e g e n e r a l i t y o f r e s u l t s s i n c e i t h a s a l r e a d y b e e n d e m o n s t r a t e d t h a t p e r f o r m a n c e i s c a t e g o r y i n d e p e n d e n t . S i n c e p o p u l a t i o n v a r i a n c e s a r e unknown t h e y must be e s t i m a t e d . A s i n p r e v i o u s t e s t s t h e y a r e assumed e q u a l . The p o o l e d s a m p l e v a r i a n c e , an u n b i a s e d e s t i m a t o r , i s s i m p l y d e f i n e d as t h e sum o f s q u a r e d d e v i a t i o n s f r o m b o t h l e f t and r i g h t - h a n d e d g r o u p s d i v i d e d by the t o t a l d e g r e e s o f f r e e d o m , i . e . , n T n„ 2 1 - 2 - 2 s = ~ [ £ (x T . - x_)Z + Z (x - v ) ] P ( n L + n R " 2 ) i - 1 L l ^ i = l ^ R ( 6 ) where s ^ = p o o l e d s a m p l e v a r i a n c e P n , n = number o f s u b j e c t s i n g r o u p s l e f t and r i g h t , i i R X^^jX^^ = i t h s u b j e c t i n g roups l e f t and r i g h t , and ^ , X R = a v e r a g e p e r f o r m a n c e i n g roups l e f t and r i g h t . 2 F o r t h e s u b j e c t s s a m p l e d , s^ was c a l c u l a t e d t o b e 1 . 6 5 . The s t u d e n t ' s t d i s t r i b u t i o n a p p l i e s f o r t h e same r e a s o n s p r o v i d e d i n t h e p r e v i o u s s e c t i o n and i s e m p l o y e d i n t h e f o l l o w i n g 95% c o n f i d e n c e i n t e r v a l f o r t h e d i f f e r e n c e i n a v e r a g e r e c o g n i t i o n p e r f o r m a n c e : w h e r e u , u = p o p u l a t i o n mean p e r f o r m a n c e p a r a m e t e r s , l i K Xj^, = g roup mean p e r f o r m a n c e t = 5% c r i t i c a l v a l u e on (n - l ) + ( n - 1 ) d e g r e e s o f f r e e d o m s = d e r i v e d p o o l e d s t a n d a r d d e v i a t i o n P and n , n = number o f s u b j e c t s i n g r o u p s l e f t and r i g h t . S i n c e t h e d i f f e r e n c e b e t w e e n l e f t - h a n d e d and r i g h t - h a n d e d s c o r e s was l e s s t h a n 2%, the o n e - s i d e d a l t e r n a t i v e h y p o t h e s i s was n o t e x a m i n e d . I n s t e a d , t h e h y p o t h e s i s , H ^ , t h a t - 4 0 , was a n a l y s e d f o r s t a t i s t i c a l , s i g n i f i c a n c e . S u b s t i t u t i n g s a m p l e d a t a i n t o E q u a t i o n (7) y i e l d s , y L - y R = 0 . 4 ± 1 .5 ( g ) 65 A c o n f i d e n c e i n t e r v a l may be r e g a r d e d as t he s e t o f a c c e p t a b l e h y p o t h e s e s , t h e r e f o r e H ^ , t h e a l t e r n a t i v e t o = ( t h e n u l l h y p o t h e s i s ) i s c l e a r l y r e j e c t e d a t t h e c l a s s i c a l 5% s i g n i f i c a n c e l e v e l . S y s t e m p e r f o r m a n c e does n o t e x h i b i t s e n s i t i v i t y to w h e t h e r t he u s e r i s r i g h t - o r l e f t - h a n d e d . 4 . 1 . 5 T r a i n i n g f o r 95% R e c o g n i t i o n A v e r a g e r e c o g n i t i o n p e r f o r m a n c e a f t e r 15 m i n u t e s o f t r a i n i n g f e l l s l i g h t l y s h o r t o f 90%. S i n c e a minimum 95% l e v e l i s u s u a l l y c o n s i d e r e d a c c e p t a b l e f o r r e a l - t i m e schemes i n w h i c h u s e r s a r e i m m e d i a t e l y made aware o f t h e c l a s s i f i c a t i o n d e c i s i o n , t h e amount o f t r a i n i n g r e q u i r e d t o a c h i e v e t h i s l e v e l was o f i n t e r e s t . A s i n g l e v o l u n t e e r f r o m e a c h s u b j e c t c a t e g o r y was a l l o w e d t o p r a c t i c e u n t i l t h e a c c e p t a b l e l e v e l was r e a c h e d . P r o g r e s s was i n i t i a l l y e n c o u r a g i n g a s t h e u s e r s q u i c k l y grew a c c u s t o m e d to pen o p e r a t i o n . As t i m e wen t on i m p r o v e m e n t s became l e s s and l e s s s i g n i f i c a n t and e r r o r s w e r e t r a c e d t o i n g r a i n e d u s e r h a b i t s w h i c h v i o l a t e d the s t r o k e f o r m a t i o n c o n s t r a i n t s o f t h e r e s t r i c t e d d i c t i o n a r y . P e r f o r m a n c e f o r e a c h s u b j e c t a f t e r 5 , 1 0 , 15 and 30 m i n u t e s o f t e s t i n g i s r e p o r t e d i n F i g . 4 . 3 . I n a d d i t i o n , t he t r a i n i n g t i m e s r e q u i r e d t o a t t a i n t h e minimum 95% p e r c e n t c l a s s i f i c a t i o n p e r f o r m a n c e a r e i n d i c a t e d . Samples o f one s u b j e c t do n o t e a s i l y l e n d t h e m s e l v e s t o s t a t i s t i c a l a n a l y s i s . One c a n a f f i r m , h o w e v e r , t h a t a l l s u b j e c t s e x c e e d e d t h e s p e c i f i e d l e v e l d u r i n g a c o m f o r t a b l e t r a i n i n g p e r i o d e x t e n d i n g f o r l e s s t h a n one h o u r . I t i s a l s o j u s t i f i a b l e t o e x t r a p o l a t e p e r f o r m a n c e t o h i g h e r l e v e l s as t h e u s e r grows more aware o f t h e few c l a s s i f i c a t i o n c o n s t r a i n t s i m p o s e d upon h i m . 66 c (Ul El c a a> > 'a E o 9750% 9500 % 96-25 % 9125 % 93-75 % • 9000 % 9250 % 9250 % 87-50 % 87-50 % 82-50 % 72-50 % 9000 % 67-50% 4750 % 67-50 % 35-00% 3000 % Prof. / Tech. 1 Prof. / Non-Tech. ' Non-Prof./Non-Tech. ' 60 50 40 30 2 0 10 Subject category F i g u r e 4.3 T e s t i n g D a t a f o r S u b j e c t s W h o s e R e c o g n i t i o n P e r f o r m a n c e A t t a i n e d 95% 67 4 . 1 . 6 C o n f u s i o n M a t r i c e s L a r g e and s m a l l i n p u t c h a r a c t e r s were c a t e g o r i z e d as c o r r e c t l y c l a s s i f i e d , m i s c l a s s i f i e d o r u n c l a s s i f i e d . R e s u l t s a p p e a r i n t h e f o r m o f c o n f u s i o n m a t r i c e s i n T a b l e s V I I I and I X . Raw d a t a i s s u m m a r i z e d i n t h e r i g h t m o s t c o l u m n s and i m p o r t a n t p e r c e n t a g e s a r e shown i n t h e l o w e r r i g h t h a n d c o r n e r s . F o u r s u b j e c t s whose r e s u l t s seemed f a i r l y c o n s i s t e n t w e r e s e l e c t e d t o p a r t i c i p a t e i n t he t e s t i n g and e n t e r e d 130 c h a r a c t e r s e a c h . A l o w sample-v a r i a n c e s u g g e s t e d t h a t s u f f i c i e n t t e s t i n g was c o n d u c t e d . The f i n a l a v e r a g e p e r f o r m a n c e s w e r e 9 6 . 9 and 96 .1% f o r l a r g e and s m a l l d i g i t s r e s p e c t i v e l y . T h e r e w e r e no "unknown t o t h e d i c t i o n a r y " c l a s s i f i c a t i o n s r e p o r t e d . T h i s i s q u i t e u n l i k e many s y s t e m s i n w h i c h t h e number o f unknowns o f t e n e x c e e d s t h e number o f m i s c l a s s i f i c a t i o n s [ C H U I 7 6 J . S i n c e t h e a u t h o r ' s d i c t i o n a r y i s v e r y t o l e r a n t to u n i n t e n t i o n a l v a r i a t i o n s , i t i s more l i k e l y t o a t t e m p t c l a s s i f i c a t i o n o f a g r o s s l y d i s t o r t e d i n p u t t h a n t o g e n e r a t e an " u n k n o w n " r e s p o n s e . M i s c l a s s i f i c a t i o n s u s u a l l y r e s u l t f r o m e x c e s s i v e a m b i g u i t y be tween c e r t a i n members o f t h e s y m b o l r e p e r t o i r e . A l t h o u g h c h a r a c t e r p a i r s o r s e t s i n w h i c h d i s c r i m i n a t i o n p r o v e s p o o r a r e r a t h e r - i l l - d e f i n e d , i t i s f a i r l y c l e a r t h a t r e s u l t s depend more on u s e r s t r o k e h a b i t s t h a n on r e c o g n i t i o n s y s t e m l i m i t a t i o n s . I t i s p o s s i b l e , t h o u g h . , t o l i s t a few o f t h e more g e n e r a l d i f f i c u l t i e s e n c o u n t e r e d by u s e r s u n f a m i l i a r w i t h t h e r e c o g n i t i o n s y s t e m : ( i ) A m a j o r s o u r c e o f e r r o r i s i n c o r r e c t p e n p o s t u r e . C l a s s i f i c a t i o n i s b a s e d o n t h e a s s u m p t i o n t h a t t h e p e n - t i p i s k e p t p e r p e n d i c u l a r t o t h e w r i t i n g medium a t a l l t i m e s . I n e x p e r i e n c e d u s e r s o f t e n h a v e TABLES V I I I AND I X CONFUSION MATRIX FOR RECOGNITION PERFORMANCE AFTER TRAINING H H 0 1 2 3 4 5 6 7 8 9 TABLE V I I I : LARGE DIGITS (> 5") 0 1 2 SYSTEM C L A S S I F I C A T I O N 3 4 5 6 7 8 9 C M U 16 16 0 0 16 16 0 0 16 16 0 0 16 16 0 0 1 15 15 1 0 13 1 2 13 3 0 16 1 16 0 0 16 16 0 .0 1 15 15 1 0 16 16 0 0 % 36-9 3-1 0 TABLE I X : SMALL DIGITS ( < | " ) o LEGEND 0 1 2 SYSTEM C L A S S I F I C A T I O N 3 4 5 6 7 8 9 C M U 36 36 0 0 35 1 35 1 0 34 1 1 34 2 0 36 36 0 0 2 33 1 33 3 0 34 1 1 34 2 0 35 1 35 1 0 1 35 35 1 0 1 35 35 1 0 1 35 35 1 0 % I96-1 3-9 0 C : CORRECTLY RECOGNIZED M : M I S C L A S S I F I E D U : U N C L A S S I F I E D 69 d i f f i c u l t y i n c o m p l y i n g b e c a u s e o f c h a n g i n g d r a g p r e s s u r e s . T h i s d i f f i c u l t y i s u s u a l l y t h e f i r s t t o d i s a p p e a r and c a u s e s few p r o b l e m s a f t e r t h e i n i t i a l f a m i l i a r i z a t i o n p e r i o d . A l t h o u g h t h e p e n b a r r e l and v a r i o u s t r a i n i n g a i d s w e r e d e s i g n e d t o f a c i l i t a t e m a i n t a i n i n g p r o p e r p e n - t i p a n g l e , a number o f s u g g e s t i o n s f o r improvement a r e m e n t i o n e d i n C h a p t e r V . ( i i ) A n o t h e r f a c t o r c o n t r i b u t i n g t o o b s e r v e d m i s -c l a s s i f i c a t i o n s s tems f r o m t h e w r i t e r ' s t e n d e n c y t o p a u s e o r h e s i t a t e a t s t r o k e e n d - p o i n t s . By e x p l a i n i n g t h a t t he p e n s e n s e s p r e s s u r e and n o t p o s i t i o n , t h e u s e r i s o f t e n m o t i v a t e d t o w r i t e i n a s m o o t h e r , c r i s p e r f a s h i o n . A f t e r s e v e r a l m i n u t e s o f p r a c t i c e p e r f o r m a n c e i m p r o v e s m a r k e d l y . ( i i i ) A l l t e s t i n g ( a p a r t f r o m t h e p e r s o n a l i z e d d i c t i o n a r y e v a l u a t i o n i n S e c t i o n 4 . 2 ) was c o n d u c t e d u s i n g t h e r e s t r i c t e d d i c t i o n a r y f o r ANSI n u m e r a l s . A l t h o u g h t h e i m p l e m e n t e d c l a s s i f i c a t i o n scheme i s i n h e r e n t l y f o r g i v i n g r e g a r d i n g s p u r i o u s d a t a , n o n - n o m i n a l c h a r a c t e r fo rms a r e o c c a s i o n a l l y m i s c l a s s i f i e d . One p o s s i b l e s o l u t i o n t o t h i s p r o b l e m w o u l d be t o " g e n e r a l i z e " t h e d i c t i o n a r y , i . e . , t o i n c r e a s e t h e number o f c h a r a c t e r fo rms e x p l i c i t l y 70 p r o v i d e d f o r . T e s t i n g was c o n d u c t e d w i t h s u c h a d i c t i o n a r y b u t no a t t e m p t was made t o q u a n t i f y t h e r e s u l t s . I n s t e a d an i n d i v i d u a l u s e r -d e d i c a t e d ( i . e . , p e r s o n a l i z e d ) s y s t e m was e x a m i n e d . S e c t i o n 4.2 i s d e v o t e d t o i n v e s t i g a t i n g t h e s a l i e n t f e a t u r e s o f s u c h a p r o p o s a l . 4-.1.7 S k i l l R e t e n t i o n S i n c e some d e g r e e o f l e a r n i n g i s r e q u i r e d b e f o r e a c c e p t a b l e s y s t e m p e r f o r m a n c e i s a t t a i n e d , t h e q u e s t i o n o f w h e t h e r o r n o t t h e u s e r m i g h t f o r g e t r e c e n t l y m a s t e r e d s k i l l s was i n v e s t i g a t e d . P s y c h o l o g i s t s t a l k o f o v e r - l e a r n e d s k i l l s w h i c h a r e r e t a i n e d l o n g a f t e r t r a i n i n g h a s b e e n c o m p l e t e d . T h e s e s k i l l s a r e a c q u i r e d by c o n t i n u i n g t r a i n i n g a f t e r t h e a c c e p t a b l e p e r f o r m a n c e l e v e l h a s b e e n r e a c h e d ; b i c y c l e r i d i n g a n d swimming a r e u s u a l l y o v e r l e a r n e d . The p o s s i b i l i t y t h a t t h e 40 m i n u t e p e n - t r a i n i n g p e r i o d i s s u f f i c i e n t f o r o v e r - l e a r n i n g , w i l l be c o n s i d e r e d n e x t . Two s u b j e c t s who a t t a i n e d the 95% a c c e p t a b l e l e v e l and who seemed t o be p e r f o r m i n g c o n s i s t e n t l y w e r e a s k e d t o u n d e r g o f u r t h e r t e s t i n g a t one week i n t e r v a l s a f t e r t h e i n i t i a l t r a i n i n g p r o g r a m . E a c h t r i a l was p r e c e d e d b y a b r i e f r e f a m i l i a r i z a t i o n p e r i o d . A summary o f d a t a o b t a i n e d a p p e a r s a s F i g . 4.4. Sample s i z e was n o t s u f f i c i e n t l y l a r g e t o a l l o w g e n e r a l c o n c l u s i o n s t o be d r a w n . I t may be n o t e d , h o w e v e r , t h a t r e s u l t s o b t a i n e d t y p i f y t h e o v e r - l e a r n i n g c o n d i t i o n , i . e . , p e r f o r m a n c e does n o t d e t e r i o r a t e s i g n i f i c a n t l y i n t h e one month f o l l o w i n g t h e t r a i n i n g p e r i o d . Immediate Testing a f te r 1 ,2 ,3 or 4 weeks A l l Training Sessions Were Preceeded by a 5 Minute Refamiliarization Period. 0 Time following training (weeks) Figure 4.4 The E f f e c t of Time Following Training  on Recognition Performance 72 A . 1 . 8 C l a s s i f i c a t i o n R o b u s t n e s s f o r N o n - N o m i n a l Forms A r e s t r i c t e d d i c t i o n a r y c o n s t r u c t e d t o c l a s s i f y c h a r a c t e r fo rms s p e c i f i e d i n the p u b l i s h e d ANSI s t a n d a r d f o r h a n d p r i n t e d d i g i t s was u sed i n the m a j o r i t y o f e x p e r i m e n t s . B e f o r e e a c h s e s s i o n s u b j e c t s were shown the ANSI s e t and a s k e d t o c o n f o r m t o t h e s e n o m i n a l s h a p e s . O c c a s i o n a l l y , s e v e r e u n i n t e n t i o n a l c h a r a c t e r d i s t o r t i o n s seemed t o be t o l e r a t e d by t h e c l a s s i f i c a t i o n p r o c e s s , i . e . , n o n - n o m i n a l forms were r e c o g n i z e d w i t h o u t c h a n g i n g t h e s t a n d a r d d i c t i o n a r y . E x p l a n a t i o n s f o r t h i s i n h e r e n t t o l e r a n c e were g i v e n i n c h a p t e r I I I . P i c t o r i a l e v i d e n c e i s p r o v i d e d i n F i g . 4 . 5 where a h a n d r a w n d i g i t a p p e a r s on t h e l e f t and on t h e r i g h t i s a p h o t o g r a p h o f t h e p r o c e s s o r ' s o u t p u t . The g e n e r a t e d d i r e c t i o n - c o d e v e c t o r , a p r e s s u r e t r a c e , and a d e c i s i o n as t o t h e i d e n t i t y o f t he i n p u t d i g i t a l s o a p p e a r i n t h e p h o t o g r a p h . The d i r e c t i o n - c o d e v e c t o r p r o v i d e s a d i r e c t measure o f how n o n -n o m i n a l t h e c h a r a c t e r i s . F o r e x a m p l e , t h e p r o c e s s o r o u t p u t f o r a n o m i n a l d i g i t two w i t h d i r e c t i o n - c o d e "RDLDRO" i s i l l u s t r a t e d i n F i g . 3 . 7 . A r a t h e r d i s t o r t e d two w i t h s l o p e - c o d e "ULURDLURDRURUO" was c o r r e c t l y r e c o g n i z e d and a p p e a r s as P l a t e (a) o f F i g . 4 . 5 . N o n - n o m i n a l e l e m e n t s o f t h e d i r e t t i o n - c o d e a r e t o l e r a t e d s u b j e c t t o t h e c o n d i t i o n t h a t t h e y do n o t i n t e r f e r e w i t h t h e c l a s s i f i c a t i o n d e c i s i o n made f o r o t h e r c h a r a c t e r s . A l t h o u g h a p r e s s u r e t r a c e i s u s e f u l i n i d e n t i f y i n g u n i n t e n t i o n a l l o c a l v a r i a t i o n s , i t i s n o t i n t e n d e d t o r e f l e c t t he e x a c t fo rm o f t h e h a n d w r i t t e n o r i g i n a l . P l a t e ( b ) , F i g . 4 . 5 , i s a c a s e i n p o i n t w h e r e t h e t r a c e b e a r s l i t t l e resemblance t o t h e o r i g i n a l ; i t i s c l e a r t h a t p e n - t i p p r e s s u r e i s n o t d i r e c t l y r e l a t e d t o pen v e l o c i t y . 73 P l a t e (a) SLOPE CODE VECTOR ULUROLMRORURUO P l a t e (b) PRESSURE INTERPRETATION OF CHARACTER ? * CODE VECTOR DLDRULO; PRESSURE INTERPRETATION OF CHARACTER S Handwritten O r i g i n a l P r o c e s s o r Output F i g u r e 4,5 R e c o g n i t i o n Performance w i t h Non-Nominal Input 74 Complex r e l a t i o n s h a v e , i n f a c t , been p o s t u l a t e d i n the t e c h n i c a l l i t e r a t u r e . W. S t a l l i n g s n o t e s t h a t " C h i n e s e c h a r a c t e r s c a n be c h a r a c t e r i z e d by c o n s t a n t a n g u l a r a c c e l e r a t i o n and a v e c t o r d i s p l a c e m e n t v e l o c i t y t h a t changes p a r a b o l i c a l l y w i t h t i m e " [ S T A L 7 5 ] . M i l l e r d i s c o v e r e d t h a t t h e w r i t i n g v e l o c i t y d i f f e r s b e t w e e n u s e r s and a l s o f o r d i f f e r e n t s y m b o l s i n s c r i b e d b y t h e same u s e r [ M I L L 6 9 ] . T h e r e seems t o be l i t t l e agreement i n t h e l i t e r a t u r e , h e n c e no e f f o r t was made t o o p t i m i z e t h e t r a c e c h a r a c t e r i s t i c s . The h a r d - c o p y o f a 3 0 0 - c h a r a c t e r t r i a l p e r f o r m e d by t h e a u t h o r a p p e a r s as A p p e n d i x A . I n t h i s s a m p l e d i s t o r t i o n s a r e f r e q u e n t ; n e v e r t h e l e s s a r e c o g n i t i o n s c o r e o f 98.7% was a c h i e v e d . A p p e n d i x B i s an example o f t he s y s t e m ' s t o l e r a n c e t o s y m b o l s i z e , s l a n t and d i s t o r t i o n . Once t h e u s e r has h a d some p r a c t i c e , s u r p r i s i n g l y s e v e r e d i s t o r t i o n s a r e e a s i l y accommodated . A l l t he c h a r a c t e r s a p p e a r i n g i n A p p e n d i x B were c o r r e c t l y c l a s s i f i e d . 4.2 C o n s t r u c t i o n o f a P e r s o n a l i z e d S y s t e m 4.2.1 I n t r o d u c t i o n S i n c e a number o f s u b j e c t s e x h i b i t e d i r r e g u l a r w r i t i n g c h a r a c t e r i s t i c s , t he p o s s i b i l i t y o f p r o v i d i n g u s e r - d e d i c a t e d r e c o g n i t i o n s y s t e m s was e x p l o r e d . I n o r d e r t o d e v e l o p and e v e n t u a l l y au tomate t h e p e r s o n a l i z a t i o n p r o c e s s , p e r f o r m a n c e s e n s i t i v i t y t o changes i n v a r i o u s s y s t e m p a r a m e t e r s i n c l u d i n g the c l a s s i f i c a t i o n d i c t i o n a r y was i n v e s t i g a t e d . Two s u b j e c t s were c h o s e n f o r t h e p u r p o s e o f r e p e t i t i v e t e s t i n g . N e i t h e r h a d b e e n t r a i n e d p r e v i o u s l y y e t b o t h p e r f o r m e d r e a s o n a b l y w e l l a f t e r s e v e r a l m i n u t e s o f p r a c t i c e . The p a r t i c i p a n t s were a s k e d t o w r i t e d i g i t s a c c o r d i n g t o A N S I s t a n d a r d s . S c o r e s were r e g i s t e r e d as f a l l i n g i n t he 80 t o 90% r a n g e . I n a s e c o n d t e s t , d i g i t s w e r e a g a i n drawn b u t t h i s t i m e no r e s t r i c t i o n s were p l a c e d on c h a r a c t e r f o r m a t i o n . S y s t e m p e r f o r m a n c e 75 s u f f e r e d c o n s i d e r a b l y , p o s s i b l y f o r t h e f o l l o w i n g r e a s o n s : i ) t h e new ' f r e e - f o r m ' c h a r a c t e r s d i d n o t f a l l w i t h i n t h e ANSI s e t and w e r e t o o e x t r e m e t o be s a v e d b y t h e i n h e r e n t t o l e r a n c e o f t h e c l a s s i f i c a t i o n s y s t e m ; i i ) s y s t e m p a r a m e t e r s t h a t h a d b e e n o p t i m i z e d f o r t h e a u t h o r and a number o f c o o p e r a t i v e c o l l e a g u e s , w e r e n o t s u i t a b l e f o r t h e s u b j e c t s b e i n g t e s t e d , i . e . , n o t a l l s y s t e m p a r a m e t e r s a r e r o b u s t . S i x e x p e r i m e n t s a r e d e s c r i b e d i n the f o l l o w i n g s e c t i o n s . I n t h e f i r s t , r e s t r u c t u r i n g the d i c t i o n a r y t r e e i s e x a m i n e d . I n t h e r e m a i n i n g s e c t i o n s , t h e e f f e c t s o f a l t e r i n g v a r i o u s s y s t e m p a r a m e t e r s a r e i n v e s t i g a t e d . The r a n g e f o r e a c h p a r a m e t e r t e s t e d was d e f i n e d t o i n c l u d e t h e o p t i m a l v a l u e d e t e r m i n e d f o r t h e a u t h o r . D e v i a t i o n s o f ±20% had a n e g l i g i b l e i n f l u e n c e on s u b j e c t p e r f o r m a n c e . P a r a m e t e r e f f e c t s w e r e assumed t o be i n d e p e n d e n t o f one a n o t h e r . The v a l i d i t y o f t h i s a s s u m p t i o n i s d i s c u s s e d i n c h a p t e r V . R e s u l t s t a b u l a t e d on the f o l l o w i n g pages r e f l e c t t h e i n f l u e n c e o f l a r g e e x c u r s i o n s . 4 . 2 .2 R e c o n f i g u r i n g the C l a s s i f i c a t i o n D i c t i o n a r y I n t h e p a s t , t e s t i n g h a d b e e n p e r f o r m e d u s i n g a r e s t r i c t e d , f i x e d d i c t i o n a r y , i . e . , t h e u s e r was r e q u e s t e d t o f o r m a l l c h a r a c t e r s i n a n o m i n a l , p r e - s p e c i f i e d f a s h i o n . C o n s t r a i n i n g t h e u s e r t o n o m i n a l fo rms d e t r a c t s f r o m the n a t u r a l n e s s o f t he w r i t i n g e n v i r o n m e n t and as s u c h i s c o n t r a r y t o a m a j o r s y s t e m d e s i g n o b j e c t i v e . 76 Crane and Savoie dealt with the problem by "generalizing" their dictionary to accomodate a larger number of character variations [CRAN77]. In this thesis the dictionary is tailored to each individual user. Since a larger generalized dictionary is inherently more prone to misclassifications (increased formation f l e x i b i l i t y for some characters can only be achieved at the expense of decreased tolerance for others), the small personalized dictionary could be expected to yield superior results. Detailed stroke patterns of the subjects r free-form digits were carefully noted. In Fig. 4.6 are shown examples of deviations from the restricted ANSI form. By redesigning the dictionary network and modifying the associated linked-list, these otherwise extraneous forms were accommodated. Results summarized i n the last row of Table X show that performance for subjects I and II increased by 42 and 24% respectively. The entire reconfiguration required approximately one hour of the author rs time. TABLE X THE EFFECT OF DICTIONARY RECONFIGURATION CHARACTER FORM/DICTIONARY RECOGNITION PERFORMANCE(%) SUBJECT I SUBJECT II Restricted Form / ANSI 85 83 Free Form / ANSI 67 75 Free Form / Reconfigured 95 93 In a non-laboratory implementation, the process of determining optimally reconfigured dictionaries would have to be automated and performed in a f a i r l y transparent manner. This problem i s addressed in Section 4.2.8. ANSI SUBJECT #1 TWO F I V E SEVEN EIGHT ANSI SUBJECT #2 THREE F I V E Figure 4 . 6 Examples of Variants of Nominal ANSI Forms 78 The e f f e c t s o f o t h e r p a r a m e t e r s t h a t d i r e c t l y i n f l u c e n c e r e c o g n i t i o n p e r f o r m a n c e a r e d i s c u s s e d n e x t . T a b l e X I summar izes t h e d a t a o b t a i n e d . TABLE X I SUMMARY OF PARAMETER S E N S I T I V I T Y I N A FREE-FORM ENVIRONMENT TEST DESCRIPTION S E J ^ C T E D PARAMETER VALUE PERFORMANCE D I F F E R E N C E ( % ) * SUBJECT I SUBJECT I I A N S I D i c t i o n a r y - 71 80 R e c o n f i g u r e d " ( R . D . ) - * 100 1 0 0 * R . D . + Change Z - T h r e s h o l d 2 U n i t s 32 U n i t s 87 84 91 91 R . D . + Change X , Y " 0 U n i t s 92 94 t 32 U n i t s 66 40 R . D . + Change Sample R a t e 5 M s e c . 97 91 + 25 M s e c . 58 75 R . D . + Change C l i p p i n g Time 0 Sec 71 67 t 0 . 2 S e c . 24 43 R . D . + Change T i m e - O u t V a l u e 0 . 2 S e c . 95 88 2 . 0 S e c . 95 1 0 2 R . D . + Change P l a n e I n c r e a s e d H o r i - 68 67 C o n f i g u r a t i o n z o n t a l T o l e r a n c e . I n c r e a s e d V e r t i -c a l T o l e r a n c e . 60 64 A L L RESULTS ARE G I V E N AS PERCENTAGES OF PERFORMANCE WITH A RECONFIGERED DICTIONARY USING GENERAL OPTIMIZED PARAMETERS f BOXED VALUES IDENTIFY HIGH USER S E N S I T I V I T Y 4 . 2 . 3 T h r e s h o l d F a c t o r s The i m p o r t a n c e o f t h r e s h o l d p r e s s u r e v a l u e s was e x p l a i n e d i n S e c t i o n 3 . 2 . F o r i n p u t d a t a t o p r o g r e s s t o s u b s e q u e n t s t a g e s , i t was r e q u i r e d t h a t Z - ( i . e . , v e r t i c a l ) p r e s s u r e e x c e e d a p r e - s p e c i f i e d v a l u e . The m a g n i t u d e o f t h e X - o r Y - component o f t h e d r a g p r e s s u r e was a l s o r e q u i r e d t o e x c e e d a c e r t a i n minimum v a l u e . P r e d e t e r m i n e d t h r e s h o l d s seemed a d e q u a t e f o r mos t 79 s u b j e c t s . I n c r e a s i n g o r d e c r e a s i n g thern d r a s t i c a l l y r e s u l t e d i n an a p p r e c i a b l e r e d u c t i o n i n s y s t e m r e c o g n i t i o n p e r f o r m a n c e . H i g h t h r e s h o l d s g r e a t l y a f f e c t w r i t e r s who g e n e r a t e l o w w r i t i n g p r e s s u r e s . Low t h r e s h o l d s r e s u l t i n an i n c r e a s e d f l o w o f d a t a ( e s p e c i a l l y f r o m s t r o k e e n d - p o i n t s ) t o l a t e r s t a g e s o f t h e c l a s s i f i c a t i o n s c h e m e . W r i t e r s who have n o t m a s t e r e d pen o p e r a t i o n and who , as a r e s u l t , g e n e r a t e s p u r i o u s d a t a a t s t r o k e end p o i n t s a r e s e v e r e l y p e n a l i z e d i n t h e l a t t e r c a s e . F i g . 4.7 i s a p e r f o r m a n c e g r a p h f o r t h e two s u b j e c t s t e s t e d . R e f e r e n c e - p o i n t p a r a m e t e r v a l u e s ( i . e . , t h o s e c h o s e n as ' g e n e r a l l y ' o p t i m a l f o r t h e a u t h o r and u s e d i n a l l p r i o r t e s t i n g ) p r o v i d e d t h e b e s t s c o r e s . I t a p p e a r s t h a t o p t i m a l t h r e s h o l d v a l u e s a r e r o b u s t w i t h r e s p e c t t o s u b j e c t p e r f o r m a n c e . P e r f o r m a n c e i s q u i t e s e n s i t i v e , h o w e v e r , t o X , Y - t h r e s h o l d v a r i a t i o n s . I n p a r t i c u l a r , h i g h v a l u e s l o w e r e d p e r f o r m a n c e c o n s i d e r a b l y f o r b o t h s u b j e c t s . A p p a r e n t l y n e i t h e r one i s a h e a v y w r i t e r . N e i t h e r s u b j e c t was h a n d i c a p p e d a t l o w t h r e s h o l d s as t h e y b o t h had l e a r n e d t o m i n i m i z e s p u r i o u s e n d - p o i n t f o r m a t i o n s . 4.2.4 S a m p l e - R a t e C o n s i d e r a t i o n s The m o d i f i e d h a r d w a r e s a m p l e d p e n p r e s s u r e e v e r y 5 m i l l i s e c o n d s . E a r l y r e s u l t s a t t he d a t a a c q u i s i t i o n phase i n d i c a t e d t h a t q u a n t i z e d d a t a w e r e r e p e a t e d f o r many c y c l e s a t t h i s r a t e . S i n c e i n c r e a s e d d a t a meant d e c r e a s e d s y s t e m r e s p o n s e t i m e , t h e l o w e s t s a m p l i n g r a t e t h a t d i d n o t r e d u c e r e c o g n i t i o n p e r f o r m a n c e was c h o s e n and u t i l i z e d i n g e n e r a l t e s t i n g . T h i s p a r a m e t e r was d e t e r m i n e d f r o m r e s u l t s f o r t h e a u t h o r and a few o b l i g i n g t e s t p a r t i c i p a n t s . 80 CO c o 4= o <U V) a e t_ o c x: G) O c a £ o l _ (1) CL O CO O CO O o UD Re fe rence 0) Leve l 0 © O LO O z 0 5 32 2 5 32 P re s su re thresho ld (Uni ts of 2"^ v o l t ) L e gend : Triangle - Subject I C i r c l e - Subject II Shaded - x-,y-Thresholds Blank - z-Threshold Figure 4.7 The E f f e c t of Changing Pre-set Pressure Thresholds 81 I n g e n e r a l , a h i g h sample r a t e s u i t s a f a s t w r i t e r . B u t a s l o w e r w r i t e r s h o u l d n o t e n c o u n t e r any d i f f i c u l t i e s a t t h i s h i g h e r r a t e i f s t r o k e e n d - p o i n t s a r e r e l a t i v e l y f r e e f rom s p u r i o u s d a t a . The f a s t e r w r i t e r , on t h e o t h e r h a n d , c o u l d e x p e c t t o p e r f o r m p o o r l y a t a l o w sample r a t e s i n c e a l a r g e p r o p o r t i o n o f h i s s h o r t - l i v e d q u a n t i z e d d i r e c t i o n s w o u l d be t r u n c a t e d by the c l i p p i n g a l g o r i t h m . E x p e r i m e n t a l r e s u l t s s u p p o r t t h e above e x p e c t a t i o n s and a r e p l o t t e d i n F i g . 4 . 8 . S u b j e c t I who p e r f o r m s w e l l a t a h i g h r a t e p e r f o r m s i n a d e q u a t e l y a t a l o w r a t e and i s u n d o u b t e d l y t h e f a s t e r w r i t e r o f t h e t w o . A g a i n , t h e b e s t p e r f o r m a n c e was s c o r e d u s i n g t h e p r e v i o u s l y c h o s e n r e f e r e n c e - p o i n t v a l u e s . 4 . 2 . 5 C l i p p i n g Time H a n d - p r i n t e d c h a r a c t e r s o f t e n e x h i b i t u n i n t e n t i o n a l e n d - p o i n t d a t a . One o f t h e d e s i g n g o a l s o f T a b l e I was t o e l i m i n a t e any s p u r i o u s i n f o r m a t i o n b e f o r e b e g i n n i n g f e a t u r e e x t r a c t i o n . An e n d - p o i n t c l i p p i n g a l g o r i t h m was a p p l i e d a f t e r t h r e s h o l d t e s t i n g t o d i s c a r d s h o r t - l i v e d e n d - p o i n t d a t a . No i n f o r m a t i o n i s l o s t i n t h e c a s e o f r e l a t i v e l y l o n g - l i v e d f o r m a t i o n s s i n c e d a t a i m m e d i a t e l y f o l l o w i n g t r u n c a t e d p o i n t s r e s o l v e t o t h e same q u a n t i z e d d i r e c t i o n . A v a l u e o f 15 m i l l i s e c o n d s o f c l i p p i n g a t b o t h ends o f e a c h s t r o k e was f o u n d t o be op t imum f o r most s y s t e m u s e r s . A f a i r l y c a r e l e s s w r i t e r w o u l d p r o b a b l y e x p e r i e n c e some d i f f i c u l t y a t l o w c l i p p i n g v a l u e s s i n c e u n i n t e n t i o n a l e n d - p o i n t d a t a w o u l d be more l i k e l y t o p r o g r e s s to s u b s e q u e n t a n a l y s i s s t a g e s . The f a s t e r w r i t e r c o u l d be e x p e c t e d t o s u f f e r a t h i g h c l i p p i n g v a l u e s s i n c e t h e p r o p o r t i o n o f t h e t o t a l c h a r a c t e r t h a t i s c l i p p e d 82 cn c CD a £ i _ o c a> o c o £ a. O O T-l o cn o co o o o IT) o Reference <X> Level A O Sample per iod ; 25 C l i p p i n g t ime: o 15 0 . 0 1 5 O A 5 ( m s e c . ) 0 . 2 5 ( sees . ) Legend Triangle C i r c l e Shaded Blank Subject I Subject II Sample Rate Clipping Time Figure 4.8 The E f f e c t of Varying Sample Rate and Clipping Time m i g h t r i s e t o t h e p o i n t t h a t a s i g n i f i c a n t amount o f n o m i n a l c h a r a c t e r i n f o r m a t i o n i s a l s o d i s c a r d e d . D a t a p l o t t e d i n F i g . 4 . 8 c o n c u r w i t h e x p e c t a t i o n s d i s c u s s e d a b o v e . Sample r a t e a n a l y s i s o f the p r e v i o u s s e c t i o n i n d i c a t e d t h a t S u b j e c t I w r i t e s f a i r l y q u i c k l y ; c o n s e q u e n t l y h i s p e r f o r m a n c e f a l l s a p p r e c i a b l y ( t o 2 4 % o f i t s r e f e r e n c e l e v e l ) as t h e amount o f d a t a c l i p p e d r i s e s . The s u b j e c t s a r e e q u a l l y a f f e c t e d i n t h e l o w c l i p p i n g s i t u a t i o n . T h i s i s r e a s o n a b l e s i n c e up u n t i l t h i s p o i n t t h e y have h a d i d e n t i c a l t r a i n i n g and a r e t h e r e f o r e e q u a l l y s k i l l e d a t a v o i d i n g u n i n t e n t i o n a l e n d - p o i n t d a t a . 4 . 2 . 6 T i m e - O u t V a l u e The t i m e - o u t v a l u e was i n t r o d u c e d t o a c c o m o d a t e m u 3 . t i p l e - s t r o k e c h a r a c t e r s ; e f f e c t s o f n o n - n o r m a l s e t t i n g s a r e a n a l y z e d h e r e . I f t he t i m e - o u t v a l u e i s s h o r t e n e d d r a m a t i c a l l y t h e u s e r f i n d s t h a t s u c c e s s i v e s t r o k e s o f m u l t i p l e - s t r o k e c h a r a c t e r s a r e n o t d e t e c t e d . The ANSI d i g i t , "S" , f o r example i s a t w o - s t r o k e s y m b o l b u t a t l o w t i m e - o u t v a l u e s t h e T i p p e r r i g h t w a r d s t r o k e i s i g n o r e d and t h e r e c o g n i z e r p o s t u l a t e s a p o o r l y d rawn e i g h t . A t h i g h v a l u e s s y s t e m r e s p o n s e t i m e i s v e r y s l o w s i n c e f o r c h a r a c t e r s whose s t r o k e s ' a r e s u b s e t s o f o t h e r s the p r o c e s s o r mus t r e s e r v e i t ' s f i n a l d e c i s i o n u n t i l t h e s y t e m r e c o g n i z e s t h e t i m e - o u t c o n d i t i o n . R e s u l t s f r o m e x p e r i m e n t a t i o n c o n f i r m t h e s e g e n e r a l i z a t i o n s . The f a s t e r w r i t e r i s l e s s p e r t u r b e d by a l o w t i m e - o u t v a l u e ; t h e s l o w e r w r i t e r i s p e n a l i z e d o n m u l t i p l e - s t r o k e s y m b o l s and p e r f o r m a n c e s c o r e s f a l l a c c o r d i n g l y . 8 4 Both writers commented that response time was intolerable in the case of high values. As expected the slower writer's performance improved even beyond the reference level since previously mis-classified multiple-stroke symbols were now classified correctly. Results are i l l u s t r a t e d in Fig. 4.9. 4.2.7 Plane Non-Uniformity Quantization plane rotation and quantization non-uniformity were mentioned in Section 3.3.2 when discussing feature extraction c r i t e r i a . Results of testing the effects of plane rotation suggested that the performance of most subjects was f a i r l y constant up until ±15° rotation then dropped abruptly. The effects of quantization non-uniformity were less consistent and are therefore analyzed here in detail. By enlarging the horizontal quadrants, characters with horizontal lines drawn poorly are more often accomodated. For example, the ANSI digit three drawn as "d" , would be recognized correctly. Similarly, variations in the v e r t i c a l direction are tolerated by enlarging the upper and lower quantization segments. The ANSI digit four drawn as, " s^ 1 , would be acceptable to this new classification system. Results are illustrated in Fig. 4.9. Subjects I and II are affected equally by the non-linear planes and neither the enlarged horizontal nor v e r t i c a l quadrants is favored. Observing the handwritten digit samples in Fig. 4.10 reveals the reason for this: characters of neither subject are slanted excessively. Again the reference level parameter optimized for the author (in this case a zero non-uniformity factor) was found to function well for both participants. 85 O ) c » —* o E t_ o c o o T - l o cn o co Reference Level a) o c o E Q. O o L O O O - 4 -A O 0 A Time-ou t To le rance short (-2) horizontal normal (-6) normal long ( 2 sec.) vert ical Legend Triangle -C i r c l e Shaded Blank Subject I Subject II Time-Out Value Stroke Direction Tolerance Figure 4.9 The E f f e c t of Varying Time-Out Value and Configuration Plane 86 Specimen I (k I £ 3 H- ^ ^ ^ & / Q S .4- 7- X 9 Specimen II I Z 3 4- 6- £ / ; V -7 / 2 3 ^ j T ^ f 7 / 3 3 ^ i T ^ T 7 • 5 * .9 ^ Figure 4.10 Specimens of Subjects' I and II Handwriting 87 4 . 2 . 8 A u t o m a t i n g t h e P e r s o n a l i z a t i o n P r o c e s s I n t h e c o u r s e o f t h e 12 p e r s o n a l i z a t i o n t r i a l s , r e f e r e n c e - l e v e l p e r f o r m a n c e a c h i e v e d u s i n g p a r a m e t e r v a l u e s o p t i m i z e d f o r t h e a u t h o r was o n l y e x c e e d e d on one o c c a s i o n . P a r a m e t e r s o p t i m i z e d f o r t h e a u t h o r p r o v e d o p t i m a l f o r b o t h s u b j e c t s . I t a p p e a r s t h a t o p t i m a l d e f i n e d s y s t e m p a r a m e t e r s a r e u s e r i n d e p e n d e n t . The i n h e r e n t l y t o l e r a n t r e s t r i c t e d d i c t i o n a r y p r o v i d e d a c c e p t a b l e r e s u l t s f o r a l l u s e r s . H o w e v e r , t he two s u b j e c t s who had d i c t i o n a r i e s d e d i c a t e d t o t h e i r p e r s o n a l w r i t i n g s t y l e s were more c o m f o r t a b l e w i t h t h e s y s t e m a n d w o u l d be more l i k e l y t o a c c e p t i t i n a n o n - l a b o r a t o r y e n v i r o n m e n t . F o r t h i s r e a s o n a l o n e , p e r s o n a l i z a t i o n i s w o r t h w h i l e . S i n c e a ma jo r c o n s i d e r a t i o n was n o n - t e c h n i c a l u s e r p e r f o r m a n c e , a t o t a l l y t r a n s p a r e n t p e r s o n a l i z a t i o n p r o c e s s was d e v i s e d . A f t e r t h e c h a r a c t e r s e t has b e e n i n p u t i n t h e n o r m a l f a s h i o n , t h e p r o c e s s o r d e c i d e s upon t h e mos t s u i t a b l e d i c t i o n a r y c o n f i g u r a t i o n and s e l e c t s o p t i m a l u s e r -d e d i c a t e d p a r a m e t e r v a l u e s . T h i s i n f o r m a t i o n i s t h e n s t o r e d u n d e r a u s e r i d e n t i f i c a t i o n number and i s r e t r i e v e d i n s u b s e q u e n t w o r k p e r i o d s . A u t o m a t i o n o f t he p e r s o n a l i z a t i o n p r o c e s s was i m p l e m e n t e d u n d e r t h e c o n s t r a i n t s o f t he m i c r o c o m p u t e r e n v i r o n m e n t d i s c u s s e d e a r l i e r i n t h e t h e s e s . P a r a m e t e r o p t i m i z a t i o n was a c h i e v e d t h r o u g h m o d i f i c a t i o n o f p a r a m e t e r v a l u e s as the t r i a l p r o c e e d e d . S i n c e t h e i n p u t c h a r a c t e r s e t h a d b e e n p r e - d e f i n e d , t h e p r o c e s s o r was a b l e t o d e t e r m i n e s u b j e c t p e r f o r m a n c e f o r e a c h o f s e v e r a l p a r a m e t e r v a l u e s . I n t h i s w a y , a s e t o f b e s t v a l u e s w e r e s e l e c t e d . A method o f a u t o m a t i c p e r s o n a l i z e d d i c t i o n a r y g e n e r a t i o n was l e s s e v i d e n t . A t e n - l e v e l s i x - l i n k p e r node t r e e r e q u i r e s i n e x c e s s o f one megabyte o f memory; c o r e r e q u i r e m e n t s a l o n e e l i m i n a t e d any p o s s i b i l i t y o f a p p l y i n g s u c h a t e c h n i q u e . F u r t h e r m o r e , t h e h a n d - c o n f i g u r e d d i c t i o n a r y u s e d i n p r e v i o u s t e s t i n g was o p t i m i z e d a t i n t e r m e d i a t e s t a g e s o f t h e p r o c e s s t h e f i n a l f o r m r e q u i r e d u n d e r 250 w o r d s . D e s i g n i n g an a l g o r i t h m t o e f f i c i e n t l y p e r f o r m t h i s f u n c t i o n w o u l d r e q u i r e c o n s i d e r a b l e e f f o r t . A n a l t e r n a t i v e scheme was e m p l o y e d w i t h s u c c e s s . A f t e r o b s e r v i n g s u b j e c t s o v e r a p e r i o d o f m o n t h s , i t became c l e a r t h a t t h e i r w r i t i n g s t y l e s c o u l d be c a t e g o r i z e d i n t o a s m a l l number o f g r o u p s . These g e n e r a l t r e n d s i n s y m b o l f o r m a t i o n may be r e g i o n a l ( S U E N 7 9 ) , p r o f e s s i o n - r e l a t e d o r p s y c h o l o g i c a l . M o d e l d i c t i o n a r i e s o f 200 t o 300 w o r d s were c o n s t r u c t e d and s t o r e d i n d i s k f i l e s . As t h e s u b j e c t p e r f o r m e d a p r e d e f i n e d w r i t i n g t a s k d i c t i o n a r i e s were i n t e r r o g a t e d s u c c e s s i v e l y . S i m u l t a n e o u s l y , p a r a m e t e r v a l u e s w e r e m o d i f i e d . The p r o c e s s o r m o n i t o r s r e c o g n i t i o n a c c u r a c y and r e p o r t s s u b j e c t p e r f o r m a n c e a t t he e n d o f t h e w r i t i n g s e s s i o n . A p r o t o t y p e s y s t e m v a r y i n g two n o n - r o b u s t p a r a m e t e r s and r e f e r e n c i n g two d i f f e r e n t d i c t i o n a r i e s was d e v e l o p e d f o r d e m o n s t r a t i o n p u r p o s e s . I n f o r m a t i o n r e l a y e d t o t h e u s e r a t s e s s i o n end ( i . e . , a f t e r 10 m i n u t e s ) i s i l l u s t r a t e d i n F i g . 4 . 1 1 . The s t a t e m e n t a t t h e b o t t o m o f t h e s c r e e n w h i c h w a r n s o f p o s s i b l e p a r a m e t e r i n t e r d e p e n d e n c e r e f l e c t s s e n t i m e n t s t h a t s h a l l be r e - i t e r a t e d i n C h a p t e r V . 4 . 3 P e r f o r m a n c e w i t h an E x t e n d e d R e s t r i c t e d D i c t i o n a r y 4 . 3 . 1 E f f e c t s upon R e c o g n i t i o n o f t h e O r i g i n a l C h a r a c t e r S e t I n t h i s s e c t i o n the ANSI r e p e r t o i r e i s e x t e n d e d t o i n c l u d e a number o f s p e c i a l c h a r a c t e r s . The a d j e c t i v e ' r e s t r i c t e d ' i s s t i l l a p p l i c a b l e s i n c e o n l y n o m i n a l c h a r a c t e r forms a r e e x p l i c i t l y d e f i n e d i n the S U B J E C T NAME ,. S T E V E WILLEY DICTIONARY* RECOGNITION PERFORMANCE AT 5 MS SAMPLE RATE -.7 RECOGNITION PERFORMANCE AT^  SS MS SAMPLE RATE i,B RECOGNITION PERFORMANCE AT LOW ORAO THRESHOLDS <B RECOGNITION PERFORMANCE AT HIGH DRAG THRESHOLDS >,B I; DICTIONARY i RECOGNITION PERFORMANCE AT S MS SAMPLE RATE -.9 RECOGNITION PERFORMANCE AT IS MS SAMPLE RATE i J RECOGNITION PERFORMANCE AT LOW DRAG THRESHOLDS ..3 RECOGNITION PERFORMANCE AT HIGH DRAG THRESHOLDS >.3 CHOICE OF OJCTJONAUr AMD OPTIMIZED *Y$TEM VARIAILtt It NOT UW-* tVlKKT, IxturricltKT FAffAHETEff INTERDEPENDENCE INFORMATION. Figure 4.11 Example of Displayed Output from the Automated Personalization Scheme „ 90 d i c t i o n a r y . The ' o r i g i n a l c h a r a c t e r s e t ' i s t h e h a n d p r i n t e d ANSI d i g i t s e t u s e d i n a l l p r e v i o u s t e s t i n g . The e f f e c t s o f d i c t i o n a r y e n l a r g e m e n t upon r e c o g n i t i o n p e r f o r m a n c e a r e e x a m i n e d h e r e . The same t h r e e s u b j e c t s who h a d p r e v i o u s l y b e e n t r a i n e d t o t h e p o i n t where t h e i r a v e r a g e s c o r e c o n s i s t e n t l y e x c e e d e d t h e 95% l e v e l w e r e a l l o w e d t o p r a c t i c e f o r 5 m i n u t e s p r i o r to f o r m a l t e s t i n g . D u r i n g t h i s p e r i o d o f r e f a m i l i a r i z a t i o n e a c h p a r t i c i p a n t was e x p o s e d t o a 9 - s y m b o l c h a r a c t e r s e t w h i c h was d e s i g n e d f o r use i n the d e d i c a t e d g r a p h i c s e d i t o r i m p l e m e n t a t i o n d i s c u s s e d e a r l i e r . The p r o f e s s i o n a l / t e c h n i c a l s u b j e c t e x p e r i e n c e d no d i f f i c u l t y i n f o r m i n g t h e new s y m b o l s ; t h e p r o f e s s i o n a l / n o n - t e c h n i c a l p a r t i c i p a n t was v a g u e l y f a m i l i a r w i t h some o f them b u t j u d g e d t h e i r c o n s t r u c t i o n more d i f f i c u l t t h a n a n t i c i p a t e d s i n c e t h e o r d e r o f m u l t i p l e s t r o k e s h a d t o be m e m o r i z e d . The n o n - p r o f e s s i o n a l / n o n - t e c h n i c a l p e r s o n h a d n e v e r s e e n t h e s y m b o l s b e f o r e and as a r e s u l t was o b l i g e d t o w r i t e s l o w e r and more h e s i t a n t l y t h a n u s u a l . I n t h e f i r s t p a r t o f t he t e s t , s u b j e c t s were a s k e d t o w r i t e f o u r t i m e s , i n a f a i r l y random f a s h i o n , t h e n u m e r i c s s e t p l u s the r e c e n t l y i n t r o d u c e d 9 - c h a r a c t e r s p e c i a l s y m b o l - s e t . No c o n s t r a i n t s w e r e p l a c e d on c h a r a c t e r s i z e o r w r i t i n g med ium. The t e s t s c o r i n g f o r m i s shown i n F i g . 4 . 1 2 and e x p e r i m e n t a l r e s u l t s a r e s u m m a r i z e d i n T a b l e X I I . G E N E R A L D I C T I O N A R Y 1 - T E S T I N G C O N S T R A I N T S P L A C E D UPON THE USER W r i t i n g S p e e d : n o n e W r i t i n g M e d i u m : n o n e S t y l i s t i c : a ) A N S I c o n f o r m i n g b ) z e r o a s 0 S y s t e m T e s t P a r a m e t e r s X , Y - P r e s s u r e T h r e s h o l d : T i n e - o u t v a l u e ( s e c ) : P l a n e N o n - 1 i n e a r i z o t l o n ( d e g ' s . ) : Z - P r e s s u r e T h r e s h o l d : C l ! p p i ng T i m e ( s e c . ) : SU3JECT C A T E G O R Y S U B J E C T I D E N T I F I E R C H A R A C T E R S I Z E T E S T S E S S -1 O N N U M B E R D I G I T 1 2 3 • l| • C M U C M U C M U c M U i ! 1 ( 1 N o t S p e c i f i e d z e r o o n e t w o t h r e e f o u r f i v e s i x s e v e n e i g h t n i n e S u b - T o t a l s R e s i s t o r C a p a c i t o r I n d u c t o r F . E . T . V . S o u r c e C . S o u r c e D E L E T E R E V E R S E F I N I S H i 1 S u b - T o t a l s I 1 j I M I ^ T O T A L S Legend: C - classified correctly . • M •» ."nisclassJfled * con forming to ANSI standards for handprinted characters li - unknown to the dictionary Figure 4.12 Testing with an Extended, Restricted Dictionary 92 TABLE X I I SUMMARY OF ANSI VERSUS EXTENDED DICTIONARY TEST RESULTS CATEGORY/ A V G . PREVIOUS ANSI I N I T I A L AVG EXTENDED •ENTIRE DICTIONARY SUBJECT D I G I T SCORE (%) DICTIONARY SCORE (%) ADDITIONAL TRAINING DIGITS ONLY ENTIRE DICTIONARY TO 95% L E V E L ( M I N . ) P r o f . / T e c h . 9 6 . 2 5 9 5 . 0 0 9 2 . 1 0 2 P r o f . /Non-T e c h . 9 5 . 0 0 9 2 . 5 0 8 4 . 2 0 10 N o n - P r o f . N o n - T e c h 9 7 . 5 0 9 6 . 2 5 8 5 . 5 2 10 S i n c e b y t h e v e r y n a t u r e o f t h e d i c t i o n a r y ' s c o n s t r u c t i o n new c h a r a c t e r s a r e accommodated a t t h e expense o f r e d u c e d f r eedom i n o t h e r s i t was s u s p e c t e d t h a t a d d i t i o n a l c h a r a c t e r fo rms m i g h t a d v e r s e l y a f f e c t c l a s s i f i c a t i o n p e r f o r m a n c e . D a t a f o r d i g i t p e r f o r m a n c e w i t h t h e A N S I d i c t i o n a r y was a v a i l a b l e f r o m p r e v i o u s t e s t s and by r e p e a t i n g t h e t r i a l s u n d e r t h e e x t e n d e d d i c t i o n a r y i t was p o s s i b l e t o draw c o n c l u s i o n s c o n c e r n i n g t h e e f f e c t s o f d i c t i o n a r y e n l a r g e m e n t . D i f f e r e n c e s i n mean p e r f o r m a n c e f o r e a c h s u b j e c t u s i n g d i f f e r e n t d i c t i o n a r i e s are a n a l y z e d b e l o w . The s a m p l e i s p a i r e d and f o r r e a s o n s g i v e n i n S e c t i o n 4 . 1 o f t h i s t h e s i s , t h e S t u d e n t ' s t d i s t r i b u t i o n w i t h n - 1 d e g r e e s o f f r e e d o m w i l l be a p p l i e d . 93 TABLE X I I I HYPOTHESIS T E S T I N G : VARYING THE DICTIONARY CATEGORY/ SUBJECT OBSERVED PERFORMANCE FOR DIGITS ONLY (%) D = ( X ^ - X 2 ) (D - D) ( D - D ) 2 X± (ANSI) X 2 ( E X T E N D ) (DIFFERENCE) P r o f . / T e c h . 9 5 . 0 0 9 5 . 0 0 0 . 0 0 - 1 . 2 5 0 1 . 5 6 3 P r o f . / N o n - T e c h . 9 5 . 0 0 9 2 . 5 0 2 . 5 0 1 . 2 5 0 1 . 5 6 3 N o n - P r o f . / N o n - T e c h . 9 7 . 5 0 9 6 . 2 5 1 .25 - 0 . 0 0 0 0 . 0 0 0 D = 1 .25 s D 2 = 1 . 5 6 3 S i n c e t h e a v e r a g e sample d i g i t s c o r e f o r t h e ANSI d i c t i o n a r y e x c e e d s t h e s c o r e u n d e r t h e e x t e n d e d d i c t i o n a r y , a o n e - s i d e d t e s t i n g p r o c e d u r e i s p r e f e r r e d . L e t t h e p o p u l a t i o n p a r a m e t e r f o r t h e d i f f e r e n c e i n s u b j e c t p e r f o r m a n c e u n d e r ANSI and E x t e n d e d d i c t i o n a r i e s be r e p r e s e n t e d b y A . T h e n , A > D - t (—) w i t h 2 d e g r e e s o f f r e e d o m ( c f . e q n . ( 5 ) ) . U J /-—I vn A > - 0 . 8 5 S i n c e A = 0 i s i n c l u d e d i n t h e c o n f i d e n c e i n t e r v a l , t h e n u l l h y p o t h e s i s , t h a t r e c o g n i t i o n p e r f o r m a n c e f o r p r e v i o u s l y e x i s t i n g c h a r a c t e r s i s n o t a d v e r s e l y a f f e c t e d by t h e d e f i n e d d i c t i o n a r y e x p a n s i o n , i s a c c e p t a b l e a t t h e c l a s s i c a l 5% s i g n i f i c a n c e l e v e l . 4 . 3 . 2 E f f e c t s upon A v e r a g e D i c t i o n a r y C l a s s i f i c a t i o n P e r f o r m a n c e P e r f o r m a n c e f o r t h e e n t i r e e x t e n d e d c h a r a c t e r s e t w a s , a t l e a s t i n i t i a l l y , l e s s e n c o u r a g i n g ; i t i s f a i r l y o b v i o u s i n e x a m i n i n g T a b l e X I I 94 t h a t d i f f i c u l t i e s were e n c o u n t e r e d w i t h t h e new s y m b o l s e t . The p r o f e s s i o n a l / t e c h n i c a l p e r s o n who had had p r e v i o u s e x p e r i e n c e d r a w i n g t h e s p e c i a l s y m b o l s s u f f e r e d l e s s t h a n h i s f e l l o w s u b j e c t s . T h i s r e s u l t i s n o t s u r p r i s i n g i n t h e l i g h t o f s e n t i m e n t s e x p r e s s e d by p s y c h o l o g i s t s who c l a i m t h a t f a m i l i a r s y m b o l s a r e more e a s i l y u n d e r s t o o d and u s e d t h a n u n f a m i l i a r s y m b o l s . U n f o r t u n a t e l y , t h i s p r e v i o u s e x p e r i e n c e r e s u l t s i n a r a t h e r l a r g e i n t e r - c a t e g o r y v a r i a n c e . R a t h e r t h a n d e f o r m t h e s t a t i s t i c b y i n c l u d i n g a b i a s e d s amp le i t i s j u s t i f i a b l e t o o m i t t h i s d a t a . W i t h t h i s m o d i f i c a t i o n r e s u l t s a p p l y o n l y f o r t h o s e s u b j e c t s u n f a m i l i a r w i t h t h e new s y m b o l s . C a l c u l a t i o n s o f the d i f f e r e n c e i n p e r f o r m a n c e f o r d i g i t s o n l y and d i g i t s p l u s s p e c i a l c h a r a c t e r s w i t h t he e x t e n d e d d i c t i o n a r y a r e i n d i c a t e d i n T a b l e X I V . TABLE X I V HYPOTHESIS TESTING: . VARYING THE SYMBOL SET ( S u b j e c t s u n f a m i l i a r w i t h e x t e n d e d s y m b o l s ) CATEGORY/ OBSERVED PERFORMANCE (%) D = ( X x - X ? ) (D - D) (D - D ) 2 SUBJECT X x (DIGITS) X 2 (ENTIRE) (DIFFERENCE) P r o f . / N o n - T e c h . 9 2 . 5 0 8 4 . 2 0 8 . 3 0 - 1 . 2 1 5 1 .48 N o n - P r o f . / N o n - T e c h . 9 6 . 2 5 8 5 . 5 2 1 0 . 7 3 1 .215 1 .48 B = 9 . 5 1 5 S d 2 = 2 . 9 6 The p o p u l a t i o n p a r a m e t e r , A , w h i c h r e p r e s e n t s t h i s d i f f e r e n c e i s b o u n d e d a s , A > D - t n ( ~ T ; ) w i t h 1 d e g r e e o f f r eedom n A > 1 .83 a t t he 5% s i g n i f i c a n c e l e v e l S i n c e A = 0 i s n o t i n c l u d e d i n t h e 5% o n e - s i d e d c o n f i d e n c e i n t e r v a l , t h e "no d i f f e r e n c e " h y p o t h e s i s i s r e j e c t e d a t t h e 5% l e v e l , i . e . , p e r f o r m a n c e o f s u b j e c t s u n f a m i l i a r w i t h t h e s p e c i a l s y m b o l s i s i n f e r i o r t o p e r f o r m a n c e w i t h common n u m e r i c s even when u s i n g t h e same d i c t i o n a r y . T h i s r e s u l t seemed t o i m p l y t h a t t h e d i c t i o n a r y was i n s u f f i c i e n t l y t o l e r a n t t o u s e r s ' u n i n t e n t i o n a l d e v i a t i o n s f r o m n o m i n a l f o r m s . A f i n a l e x p e r i m e n t was d e f i n e d i n o r d e r t o t e s t t h i s p o s s i b i l i t y . E a c h s u b j e c t was a s k e d to p r a c t i c e w r i t i n g the s p e c i a l c h a r a c t e r f o r m s u n t i l r e c o g n i t i o n p e r f o r m a n c e h a d i m p r o v e d t o the p r e v i o u s l y a t t a i n e d 95% l e v e l . The p r o f e s s i o n a l / t e c h n i c a l s u b j e c t q u i c k l y e l i m i n a t e d h i s p r o b l e m s and a c h i e v e d t h e 95% l e v e l a f t e r a b r i e f 3 m i n u t e t r a i n i n g p e r i o d . The o t h e r two s u b j e c t s d i s c o v e r e d t h a t t h e i r d i f f i c u l t i e s stemmed f r o m a r e d u c e d w r i t i n g s p e e d (hence more good and b a d d a t a a c q u i r e d ) d i c t a t e d b y t h e i r u n f a m i l i a r i t y w i t h t h e new s y m b o l s e t ; e a c h a t t a i n e d t h e a c c e p t a b l e l e v e l o f 95% a f t e r 10 m i n u t e s o f p r a c t i c e . D e s p i t e i n i t i a l d i f f i c u l t i e s , a l l s u b j e c t s q u i c k l y a d a p t e d t o the new s y m b o l s e t . I t i s c o n c l u d e d , t h e r e f o r e , t h a t t h e i n i t i a l r e d u c t i o n i n r e c o g n i t i o n p e r f o r m a n c e was d i r e c t l y r e l a t e d t o the s u b j e c t s ' u n f a m i l i a r i t y w i t h t h e new t a s k and n o t t o any i n h e r e n t weakness o f t h e c l a s s i f i c a t i o n s c h e m e . I t mus t be k e p t i n m i n d , h o w e v e r , t h a t t h e s e r e s u l t s a r e p a r t i c u l a r t o the d e s c r i b e d e x p e r i m e n t , i . e . , t h e e n l a r g i n g o f a d i c t i o n a r y f r o m 10 t o 19 c h a r a c t e r s , and a r e n o t n e c e s s a r i l y a p p l i c a b l e t o l a r g e r c h a r a c t e r s e t s . N o n e t h e l e s s , p e r s o n a l i z a t i o n s h o u l d i m p r o v e s y s t e m p e r f o r m a n c e by r e d u c i n g the t o t a l number o f f o r m s t h a t must be e x p l i c i t l y accommodated by t h e d i c t i o n a r y . T h i s i s even more t r u e i f t h e d e s i g n e r i s a l l o w e d some f r eedom and f l e x i b i l i t y i n s y m b o l d e f i n i t i o n . 96 V . CONCLUDING REMARKS 5 . 1 Summary o f E x p e r i m e n t a l R e s u l t s T e s t i n g w i t h t h e ANSI r e s t r i c t e d d i c t i o n a r y was c o n d u c t e d on a t o t a l o f 15 s u b j e c t s and r e s u l t s f o r o v e r 4000 i n p u t c h a r a c t e r s w e r e g a t h e r e d . Two s u b j e c t s w e r e l a t e r s e l e c t e d d u r i n g p e r s o n a l i z a t i o n t r i a l s and a f u r t h e r 1000 c h a r a c t e r s w e r e o b t a i n e d . F i n a l l y , t h e e x t e n d e d s y m b o l s e t was t e s t e d on 3 p r e v i o u s l y t r a i n e d s u b j e c t s and an a d d i t i o n a l 400 r e c o g n i t i o n d e c i s i o n s w e r e n o t e d . The d e s i g n p r o v i d e s a n a t u r a l e n v i r o n m e n t f o r man-mach ine c o m m u n i c a t i o n , a m a j o r o b j e c t i v e o f t h i s t h e s i s . S i n c e u s e r s w e r e n o t d i s t r a c t e d b y o p e r a t i o n a l f a c t o r s t h e y w e r e a b l e to a p p l y t h e m s e l v e s t o t h e d e s i g n a t e d w r i t i n g t a s k w i t h a p p a r e n t e a s e . The t e s t i n g s e s s i o n was f u l l y a u t o m a t e d and most s u b j e c t s were a b l e t o e n t e r d i g i t s a t j u s t s l i g h t l y b e l o w t h e i r n o r m a l w r i t i n g r a t e . Owing t o the s m a l l amount and s i m p l i c i t y o f h a r d w a r e i n v o l v e d , e v e n n o n - t e c h n i c a l u s e r s were c o m f o r t a b l e i n t h e p e n - p a p e r e n v i r o n m e n t and grew p r o g r e s s i v e l y more c o n f i d e n t as t r a i n i n g c o n t i n u e d . They w e r e p o s i t i v e l y m o t i v a t e d by t h e i r i m p r o v i n g r e c o g n i t i o n a c c u r a c y s c o r e s and t h e y a l l f e l t t h a t c h a r a c t e r s e t c o n s t r a i n t s were a c c e p t a b l e , e a s i l y u n d e r s t o o d , and t h a t t h e y d i d n o t d e t r a c t f r o m t h e n a t u r a l n e s s o f t h e s y s t e m . I t seems t h a t the p e n w o u l d be most s u i t a b l e i n a s i t u a t i o n where u s e r s had p r e v i o u s l y a c h i e v e d a c c e p t a b l e r e s u l t s . The b r i e f t r a i n i n g p e r i o d a l l o w s the u s e r t o r e d u c e u n i n t e n t i o n a l e n d - p o i n t d a t a t h a t m i g h t o c c a s i o n a l l y g e n e r a t e s p u r i o u s c l a s s i f i c a t i o n s . 97 D u r i n g t e s t i n g , any i n i t i a l d i f f i c u l t i e s were q u i c k l y ove rcome and t h e o p e r a t o r p r o g r e s s e d i n a p p r o x i m a t e a c c o r d a n c e w i t h c l a s s i c a l e x p o n e n t i a l l e a r n i n g c u r v e s t a t i s t i c s , a t t a i n i n g a r e c o g n i t i o n a c c u r a c y o f 90% a f t e r 15 m i n u t e s o f t r a i n i n g . A l t h o u g h t e c h n i c a l u s e r s p e r f o r m e d b e t t e r t h a n n o n - t e c h n i c a l u s e r s i n i t i a l l y , p e r f o r m a n c e a f t e r 15 m i n u t e s o f p r a c t i c e was a l m o s t i d e n t i c a l . S e n s i t i v i t y t o s u b j e c t c a t e g o r y was c a r e f u l l y a n a l y z e d b y a p p l y i n g a n a l y s i s o f v a r i a n c e c a l c u l a t i o n s t o t h e l a r g e q u a n t i t y o f d a t a o b t a i n e d . I n f e r e n c e s w e r e c o n c l u s i v e : a f t e r 15 m i n u t e s o f t r a i n i n g , u s e r p e r f o r m a n c e was i n d e p e n d e n t o f u s e r c a t e g o r y . A p r i m a r y s y s t e m d e s i g n o b j e c t i v e i s met i n t h a t a l m o s t a l l u s e r s a r e c a p a b l e o f c o m m u n i c a t i n g n a t u r a l l y u n d e r t h e p r o p o s e d e n v i r o n m e n t . 3 The h y p o t h e s i s t h a t l a r g e c h a r a c t e r s ( t a l l e r t han —") a r e more o f t e n c o r r e c t l y r e c o g n i z e d t h a n s m a l l c h a r a c t e r s was e x a m i n e d . S i n c e p e r f o r m a n c e i n d e p e n d e n c e t o s y m b o l s i z e was a l s o a d e s i g n s p e c i f i c a t i o n ( T a b l e I , O b j e c t i v e #3), t h e need t o c o m p e t e n t l y t e s t t h i s f e a t u r e was i m p o r t a n t . A s t a t i s t i c a l a n a l y s i s was a g a i n p e r f o r m e d . D a t a w e r e o b t a i n e d f o r e a c h u s e r c a t e g o r y d u r i n g and a f t e r t h e b r i e f t r a i n i n g s e s s i o n . The s t a t e d h y p o t h e s i s was r e j e c t e d f o r a l l t h r e e c a t e g o r y g r o u p s ( P r o f e s s i o n a l / T e c h n i c a l , P r o f e s s i o n a l / N o n - T e c h n i c a . l and N o n - P r o f e s s i o n a l / N o n - t e c h n i c a l ) d u r i n g t h e t r a i n i n g p e r i o d b u t a c c e p t e d , i n d e p e n d e n t o f u s e r g r o u p , a f t e r 15 m i n u t e s o f t r a i n i n g . A s l i g h t r e d u c t i o n i n p e r f o r m a n c e f o r s m a l l c h a r a c t e r s was r e c o r d e d f o r t he p r a c t i c e s e s s i o n . F o r t u n a t e l y t h i s d i f f e r e n c e i n p e r f o r m a n c e was s h o r t - l i v e d a n d , i n f a c t , n o n - e x i s t a n t a t t he end o f t h e t r a i n i n g s e s s i o n . E x a m p l e s o f v e r y l a r g e and v e r y s m a l l c o r r e c t l y c l a s s i f i e d d i g i t s a p p e a r as A p p e n d i x B . I t i s p e r h a p s w o r t h n o t i n g t h a t l a r g e c h a r a c t e r s a r e n o t l i m i t e d t o 1 cm. o r e v e n 10 cm. i n h e i g h t . B e c a u s e o f t h e c h o s e n f e a t u r e e x t r a c t i o n s c h e m e , c h a r a c t e r s i z e i n d e p e n d e n c e i s f a i r l y a b s o l u t e . L e f t - and r i g h t - h a n d e d p e o p l e h o l d t h e i r pens d i f f e r e n t l y . S i n c e c o r r e c t p e n p o s t u r e was f o u n d t o be a p r e - r e q u i s i t e f o r good r e c o g n i t i o n p e r f o r m a n c e and s i n c e t h e s u g g e s t e d X e b e c p e n p o s t u r e c l o s e l y r e s e m b l e s t h a t p r e f e r r e d by a r i g h t - h a n d e d p e r s o n , l e f t - h a n d e d p e o p l e m i g h t e x p e r i e n c e d i s c o m f o r t o r d i f f i c u l t y and c o n s e q u e n t l y p e r f o r m p o o r l y i n w r i t i n g t a s k s . D a t a o b t a i n e d d u r i n g and a f t e r t h e t r a i n i n g s e s s i o n s f o r l e f t - and. r i g h t -h a n d e d p e o p l e w e r e c o m p a r e d . R e c o g n i t i o n p e r f o r m a n c e was n o t f o u n d t o b e s e n s t i v e t o w h e t h e r t h e u s e r was r i g h t - o r l e f t - h a n d e d . D u r i n g t h e i n i t i a l s h o r t t r a i n i n g p e r i o d , t he m a j o r i t y o f s u b j e c t s t e s t e d w e r e n o t a b l e t o a c h i e v e t h e a c c e p t a b l e r e c o g n i t i o n l e v e l o f 95% c i t e d i n c u r r e n t l i t e r a t u r e [ M I L L 6 9 , C H U I 7 6 ] . Two q u e s t i o n s t h u s r a i s e d w e r e : ( i ) C o u l d t h e a c c e p t a b l e l e v e l e v e r be a c h i e v e d u n d e r t h e e x i s t i n g h a r d w a r e / s o f t w a r e s y s t e m d e s i g n ? And i f s o , ( i i ) How l o n g w o u l d the a v e r a g e u s e r have t o p r a c t i c e b e f o r e a t t a i n i n g the 95% p e r f o r m a n c e l e v e l ? T e s t p a r t i c i p a n t s were c h o s e n f r o m d i f f e r e n t u s e r c a t e g o r i e s and a l l o w e d t o p r a c t i c e b e y o n d t h e n o r m a l 15 m i n u t e l i m i t . R e s u l t s a p p e a r i n g i n F i g . 4 . 3 e x p r e s s p e r f o r m a n c e l e v e l s a t v a r i o u s s t a g e s o f t r a i n i n g . A l l s u b j e c t s t e s t e d a t t a i n e d t h e 95% l e v e l w i t h l e s s t h a n one h o u r o f p r a c t i c e . F u r t h e r m o r e , r e c o g n i t i o n p e r f o r m a n c e a l w a y s i m p r o v e d w i t h f u r t h e r p r a c t i c e . A p p e n d i x A i l l u s t r a t e s a 300 c h a r a c t e r r e c o g n i t i o n a c c u r a c y t r i a l i n w h i c h o v e r a l l p e r f o r m a n c e e x c e e d s 9 8 % . S k e p t i c s o f t h e s y s t e m c l a i m e d t h a t any scheme r e q u i r i n g l e a r n i n g on t h e p a r t o f t h e o p e r a t o r was i n h e r e n t l y d e f i c i e n t i n t h a t o c c a s i o n a l u s e r s w o u l d s p e n d more t i m e t r a i n i n g t h a n o p e r a t i n g . To t e s t t h i s h y p o t h e s i s , s u b j e c t s w e r e a s k e d t o r e t u r n a t one week i n t e r v a l s . A t e a c h s e s s i o n t h e y w e r e a s k e d t o p e r f o r m a s m a l l w r i t i n g t a s k ; t e s t r e s u l t s a r e i l l u s t r a t e d i n F i g . 4 . 4 . P e r f o r m a n c e f o r o c c a s i o n a l u s e r s d i d n o t d i f f e r m a r k e d l y o v e r t h e one month p e r i o d f o l l o w i n g i n i t i a l t r a i n i n g . U s i n g the X e b e c p e n c o u l d be c l a s s i f i e d as a "once l e a r n e d a l w a y s r e t a i n e d " ( i . e . , o v e r - l e a r n e d ) s k i l l . C o n v e n t i o n a l c o n f u s i o n m a t r i c e s were c o n s t r u c t e d i n o r d e r t o q u a n t i f y r e c o g n i t i o n p e r f o r m a n c e . S c o r e s a v e r a g e d 9 6 . 5 % f o r u s e r s who were f a m i l i a r b u t o n l y s l i g h t l y e x p e r i e n c e d w i t h t h e ANSI n u m e r i c s c h a r a c t e r s e t . The c o n f i g u r e d d i c t i o n a r y was f a i r l y r e s t r i c t e d i n t h a t t he number o f e x p l i c i t l y accommodated d e v i a t i o n s f r o m n o m i n a l fo rms was q u i t e l o w . O b s e r v e d t o l e r a n c e t o l o c a l d e v i a t i o n s was t h e r e f o r e more due t o d i c t i o n a r y s t r u c t u r e t h a n t o c o n t e n t . A l t h o u g h an "Unknown" r e s p o n s e i s i n c l u d e d i n . t he d e c i s i o n r e p e r t o i r e , i t n e v e r o c c u r e d d u r i n g c o n f u s i o n m a t r i x t e s t i n g . The r e c o g n i t i o n scheme was f o u n d t o be v e r y t o l e r a n t t o u n i n t e n t i o n a l v a r i a t i o n s and d i s t o r t i o n s . E x a m p l e s o f a c c e p t a b l e d i s t o r t i o n s a r e i l l u s t r a t e d i n F i g . 4 . 6 and i n A p p e n d i x B . A few s u b j e c t s f o u n d t h e A N S I n u m e r i c s s e t awkward t o c o n f o r m t o and c o m p l a i n e d t h a t t h e c o n s t r a i n t s d e t r a c t e d f r o m an o t h e r w i s e n a t u r a l e n v i r o n m e n t . F o r t h e s e p e o p l e , d e d i c a t e d o r p e r s o n a l i z e d d i c t i o n a r i e s t h a t e x p l i c i t l y accommodated t h e i r n o n - n o m i n a l ANSI fo rms were c o n f i g u r e d . Upon r e t e s t i n g , t h e i r r e c o g n i t i o n p e r f o r m a n c e i m p r o v e d by an a v e r a g e o f a l m o s t 100 A t o t a l o f s i x s y s t e m p a r a m e t e r s were i n d i v i d u a l l y e x a m i n e d f o r t h e i r e f f e c t s upon r e c o g n i t i o n p e r f o r m a n c e . A l t h o u g h e x t r e m e v a l u e s o f t e n s e v e r e l y i n f l u e n c e d t e s t i n g s c o r e s , p a r a m e t e r s o p t i m i z e d f o r a. s m a l l g roup o f u s e r s were f o u n d t o be o p t i m a l f o r a l l s u b j e c t s o f t h e g roup t e s t e d . S u c h r o b u s t n e s s i s a d e s i r a b l e q u a l i t y i n any s y s t e m . Some u s e r s who e x h i b i t e x c e p t i o n a l w r i t i n g c h a r a c t e r i s t i c s ( l i g h t , f a s t o r c a r e l e s s , f o r e x a m p l e ) can b e n e f i t f r o m p a r a m e t e r f i n e - t u n i n g . S i n c e t h e n o n - t e c h n i c a l u s e r c a n n o t be e x p e c t e d t o p e r f o r m s y s t e m m o d i f i c a t i o n s t h e p e r s o n a l i z a t i o n p r o c e s s has b e e n f u l l y au toma ted and p r o c e e d s a l m o s t unknown t o t h e u s e r . T r a n s p a r e n c y o f t e c h n i c a l d e t a i l s was a p r i m e c o n s i d e r a t i o n i n d e s i g n i n g t h i s s y s t e m . One o f many a d v a n t a g e s t h e p e n h a s o v e r t h e k e y b o a r d i s r e l a t e d t o n o n - s t a n d a r d s y m b o l d e f i n i t i o n . S p e c i a l l y c o n s t r u c t e d f u n c t i o n pads o r e x t e n d e d k e y b o a r d s t e n d t o be e x p e n s i v e w h e r e a s r e c o n f i g u r i n g d i c t i o n a r y s o f t w a r e i s a s i m p l e t a s k f o r t h e q u a l i f i e d c o m p u t e r p r o g r a m m e r . A l t h o u g h a t t h e p r e s e n t t i m e s y m b o l s a r e n o t u s e r r e - d e f i n a b l e t h e y c a n be d e d i c a t e d t o t h e u s e r ' s needs a t t he t i m e o f d i c t i o n a r y c o n s t r u c t i o n . H o w e v e r , many u s e r s may be s a t i s f i e d w i t h a s t a n d a r d ANSI n u m e r i c s s e t p l u s 8 t o 10 s p e c i a l c h a r a c t e r s . T e s t s were c o n d u c t e d t o d e t e r m i n e i f d o u b l i n g s y m b o l s e t s i z e had any i n f l u e n c e on u s e r s ' r e c o g n i t i o n p e r f o r m a n c e . A 1 9 - s y m b o l s e t i n t e n d e d f o r the i n t e r a c t i v e g r a p h i c s i m p l e m e n t a t i o n d e s c r i b e d i n C h a p t e r I I was d e s i g n e d and t e s t e d u n d e r s i m u l a t e d c o n d i t i o n s . A s t a t i s t i c a l a n a l y s i s o f r e s u l t i n g p e r f o r m a n c e d a t a r e v e a l e d t h a t the i n c r e a s e i n d i c t i o n a r y s i z e had no e f f e c t on r e c o g n i t i o n s c o r e s o b t a i n e d f o r t h e o r i g i n a l n u m e r i c c h a r a c t e r s e t . Nor was a v e r a g e ( i . e . , t a k e n o v e r 19 c h a r a c t e r s ) d i c t i o n a r y p e r f o r m a n c e i n f l u e n c e d , a l t h o u g h 101 s c o r e s d i d f a l l i n i t i a l l y s i n c e u s e r s were n o t a c c u s t o m e d t o d r a w i n g members o f t h e s p e c i a l s y m b o l s e t . 5 . 2 A c h i e v e d D e s i g n O b j e c t i v e s W i t h t h e r e c o g n i t i o n scheme c o m p l e t e d and p e r f o r m a n c e r e s u l t s a v a i l a b l e , i t was p o s s i b l e t o e v a l u a t e t h e s y s t e m i n t h e l i g h t o f e x p r e s s e d d e s i g n o b j e c t i v e s . I n t h e p a r a g r a p h s t h a t f o l l o w , c h a r a c t e r i s t i c s e n u m e r a t e d i n T a b l e I a r e d i s c u s s e d i n d i v i d u a l l y ; t h o s e c o n s i d e r e d f a v o r a b l e a r e d e a l t w i t h f i r s t . 5 . 2 . 1 F a v o r a b l e C h a r a c t e r i s t i c s 1) The f i r s t o b j e c t i v e , r e a l - t i m e o p e r a t i o n , i s f u l f i l l e d . By p e r f o r m i n g a c q u i s i t i o n and p a t t e r n a n a l y s i s c o n c u r r e n t l y , s y s t e m r ' esponse t i m e i s s u f f i c i e n t l y f a s t t o a l l o w o n - l i n e r e c o g n i t i o n . 2) P r o c e s s i n g on a p o i n t - b y - p o i n t b a s i s was a l s o a d o p t e d . I n s t e a d o f d e l a y i n g a n a l y s i s u n t i l e n t i r e s t r o k e s o r c h a r a c t e r s h a v e b e e n i n p u t , p r e - p r o c e s s i n g , f e a t u r e e x t r a c t i o n and p a r t i a l c l a s s i f i c a t i o n a r e p e r f o r m e d i m m e d i a t e l y a f t e r t h e p r e s s u r e v e c t o r i s o b t a i n e d . By p r o c e e d i n g i n t h i s f a s h i o n , r e d u n d a n t d a t a a r e d i s c a r d e d e a r l y i n t h e p r o c e s s o b v i a t i n g t h e need f o r i n t e r m e d i a t e s t o r a g e . The f a c t t h a t a r e c o g n i t i o n d e c i s i o n may be made v e r y s h o r t l y a f t e r a c q u i r i n g the f i n a l p r e s s u r e v a l u e i s an added a d v a n t a g e (and o c c a s i o n a l l y t h e d e c i s i o n i s r e n d e r e d b e f o r e t h e f i n a l p o i n t i s s a m p l e d ) . 3) The c l a s s i f i c a t i o n scheme e m p l o y e d i n the a u t h o r ' s s y s t e m i s i n h e r e n t l y i n s e n s i t i v e t o s i z e v a r i a t i o n s s i n c e p o s i t i o n a l i n f o r m a t i o n i s n o t a n a l y z e d . T h i s i n d e p e n d e n c e i s a l m o s t w i t h o u t q u a l i f i c a t i o n ; u s e r s who a r e m o d e r a t e l y f a m i l i a r w i t h t h e s y s t e m p e r f o r m i n d i f f e r e n t l y w i t h c h a r a c t e r s 102 o f 1mm and l m . E x a m p l e s o f r e a s o n a b l y e x t r e m e s y m b o l s i z e s a p p e a r i n A p p e n d i x B w h e r e a l l c h a r a c t e r s were c o r r e c t l y r e c o g n i z e d . 4) S i n c e s p u r i o u s e n d - p o i n t d a t a a r e t r e a t e d b e f o r e and n o t a f t e r f e a t u r e e x t r a c t i o n , t h e f o u r t h o b j e c t i v e i s a l s o f u l f i l l e d . T h i s a p p r o a c h r e d u c e s t h e o v e r a l l c o m p u t i n g b u r d e n s i n c e t h e q u a n t i t y o f d a t a p a s s e d t o s u b s e q u e n t s t a g e s i s l o w e r e d and t h e c o m p l e x i t y o f l a t e r s t a g e s i s r e d u c e d . A l a r g e p r o p o r t i o n o f t he r e s e a r c h e f f o r t was expended i n o p t i m i z i n g t h e p r e - p r o c e s s i n g s t a g e . 5) B e r n s t e i n and H o w e l l c l a i m e d t h a t a p r a g m a t i c a p p r o a c h was a d v a n t a g e o u s t o the d e s i g n o f a p r a c t i c a l r e c o g n i t i o n s y s t e m [ B E R N 6 9 ] , The a u t h o r a d o p t e d s u c h an a p p r o a c h ; e a c h d e s i g n s t e p r e s o l v e d t o j u s t i f y i n g any d e c i s i o n s made, i m p l e m e n t i n g , f i n e - t u n i n g and t h e n t e s t i n g t h e f i n a l v e r s i o n . 6) M i l l e r ' s scheme e x h i b i t e d some p e r f o r m a n c e i n s e n s i t i v i t y t o c h a r a c t e r s l a n t and p o s i t i o n [ M I L L 6 9 ] . P e r f o r m a n c e w i t h t h e X e b e c p e n i s e n t i r e l y i n d e p e n d e n t o f p o s i t i o n and i s v e r y t o l e r a n t t o o v e r a l l s l a n t , g r o s s d i s t o r t i o n s and f a i r l y s e v e r e r o t a t i o n s o w i n g t o the c o u r s e d i r e c t i o n q u a n t i z a t i o n scheme w i t h 1 6 ° h y s t e r s i s a t segment b o r d e r s . A t e c h n i q u e f o r p r o v i d i n g e v e n g r e a t e r t o l e r a n c e t o c h a r a c t e r r o t a t i o n i s o u t l i n e d i n S e c t i o n 5 . 5 . 7) A l t h o u g h L e d e e n ' s s y s t e m s u f f e r e d s e v e r a l major d r a w b a c k s ( e g . a l p h a n u m e r i c s U and V were i n d i s t i n g u i s h a b l e ) , t h e f e a s i b i l i t y o f i m p l e m e n t i n g w i t h l o w CPU and l o w memory r e q u i r e m e n t s was w e l l e s t a b l i s h e d [ L E D E 7 3 ] . The a u t h o r h a s r e s t r i c t e d h i s s y s t e m i n a s i m i l a r f a s h i o n . Memory r e q u i r e m e n t s a r e m i n i m a l ( d i s c u s s e d l a t e r ) and t h e CPU b u r d e n i s m i c r o c o m p u t e r c o m p a t i b l e . Not a l l p r e v i o u s l y r e p o r t e d s y s t e m s o p e r a t e i n modest e n v i r o n m e n t s . G r o n e r , f o r e x a m p l e , u t i l i z e s an IBM S y s t e m 360 t o i m p l e m e n t an 8 - t u p l e f e a t u r e e x t r a c t i o n p r o c e s s ; a s i n g l e f e a t u r e was f o u n d t o b e s u f f i c i e n t f o r t he X e b e c p e n - b a s e d s y s t e m . 8) I n C h u i ' s t h e s i s a r e s e v e r a l pages o f s u c c e s s f u l l y r e c o g n i z e d i n t e n t i o n a l l y d i s t o r t e d c h a r a c t e r s [ C H U I 7 6 ] . The a u t h o r ' s s y s t e m i s n o l e s s t o l e r a n t t o e i t h e r l o c a l o r g r o s s v a r i a t i o n s as e v i d e n c e d by e x a m p l e s i n A p p e n d i x B . 9) C h u i ' s scheme e x h i b i t e d a s e c o n d f a v o r a b l e c h a r a c t e r i s t i c , m i n i m a l u s e r t r a i n i n g . He r e p o r t e d t h a t u s e r s h a d no d i f f i c u l t y o p e r a t i n g t h e p e n a f t e r a few m i n u t e s o f p r a c t i c e . T h i s i s n o t t h e c a s e f o r Rand t a b l e t s y s t e m s where the o p e r a t o r must v i e w a CRT w h i l e w r i t i n g o n a t a b l e t and r e q u i r e s a minimum o f an h o u r o f t r a i n i n g . The a u t h o r ' s scheme r e q u i r e s some f a m i l i a r i z a t i o n . P e r f o r m a n c e s t a b i l i z e s a f t e r a p p r o x i m a t e l y 15 m i n u t e s a l t h o u g h i t i m p r o v e s s l i g h t l y w i t h i n c r e a s e d t r a i n i n g . F o r t u n a t e l y t h e s k i l l seems t o be e a s i l y r e t a i n e d by o p e r a t o r s , i . e . t h e l e a r n i n g p e r i o d s h o u l d n o t have t o be r e p e a t e d . 10) A s w i t h C r a n e ' s s y s t e m , t h e X e b e c p e n - b a s e d scheme i s e n t i r e l y m i c r o c o m p u t e r c o m p a t i b l e [ C R A N 7 7 ] . CPU and memory r e q u i r e m e n t s h a v e b e e n k e p t t o a m in imum. A c o m p l e t e s y s t e m w o u l d c o m p r i s e the f o l l o w i n g : 1 8 - b i t CPU 3 k Rom 512 RAM 1 S e r i a l i n t e r f a c e d e v i c e 1 D i s p l a y ( L E D , L C D , e t c . ) S e v e r a l T T L g a t e s 104 A l l 10 f a v o r a b l e c h a r a c t e r i s t i c s o f o t h e r s y s t e m s have b e e n i n c o r p o r a t e d i n t o t h e p r o p o s e d scheme. The o t h e r 12 c h a r a c t e r i s t i c s w h i c h were t o b e e l i m i n a t e d f r o m t h e d e s i g n a r e d i s c u s s e d n e x t . 5 . 2 . 2 E l i m i n a t i o n o f U n d e s i r a b l e C h a r a c t e r i s t i c s 1) H o s k i n g s e l e c t e d a f a i r l y u n a m b i g u i o u s c h a r a c t e r s e t f o r t h e p u r p o s e o f s y s t e m t e s t i n g . A s i d e f rom d i g i t s z e r o t o n i n e he h a d s u b j e c t s e n t e r l e t t e r s C , S , T , X and Z w h i c h a r e q u i t e d i s s i m i l a r and t h u s e a s i l y r e c o g n i z a b l e . The a u t h o r t r i e d t o a v o i d t h i s r e s t r i c t i o n by i n c l u d i n g c e r t a i n p o t e n t i a l l y ambiguous c h a r a c t e r p a i r s , e . g . I>yv0', ' -W^ ' and " " " ( t h e l a t t e r p a i r i s ambiguous s i n c e the s e c o n d s t r o k e o f = may be n e g l e c t e d i f t i m e - o u t o c c u r s ) . 2) S i n c e he had a c c e s s t o e x t e n s i v e f a c i l i t i e s a h e a v y c o m p u t i n g b u r d e n was n o t c o n s i d e r e d t o be a s y s t e m l i m i t a t i o n . The a u t h o r ' s scheme was d e s i g n e d t o o p e r a t e i n a s m a l l m a c h i n e e n v i r o n m e n t . By e x t r a c t i n g o n l y one t y p e o f f e a t u r e (a 4 - d i r e c t i o n i n d i c a t o r ) and s i m p l i f y i n g a n a l y s i s c a l c u l a t i o n s , t he r e q u i r e d c o m p u t i n g f a c i l i t i e s a r e m i n i m a l . 3) I t i s d e s i r a b l e t o p r o v i d e an e n v i r o n m e n t t h a t does n o t c o n s t r a i n t h e u s e r . T h i s i d e a h e l p e d m o t i v a t e t he a u t h o r ' s d e s i g n o f p e r s o n a l i z e d s y s t e m s . G r o n e r ' s scheme i m p o s e d f a i r l y s e v e r e s t y l i s t i c c o n s t r a i n t s w h i c h c o u l d r e d u c e u s e r a c c e p t a n c e o f t h e s y s t e m . I n t h e X e b e c p e n - b a s e d scheme a s i n g l e c o n s t r a i n t was s t i p u l a t e d : an o e r s t e d w o u l d r e p l a c e z e r o . 4) I n B e r n s t e i n ' s r e c o g n i t i o n s y s t e m , c l a s s i f i c a t i o n was p e r f o r m e d on two l e v e l s [BERN68] . Unknown i n p u t s were f i r s t i d e n t i f i e d as p r i m i t i v e s t r o k e s then r e l a t i o n s be tween the s t r o k e s w e r e c a l c u l a t e d . D i v i d i n g c h a r a c t e r s i n t o s t r o k e s seemed t o be an u n n e c e s s a r y s t e p and i s 105 t h e r e f o r e n o t c o n t a i n e d i n t h e p r o p o s e d s y s t e m . 5) The h i g h memory r e q u i r e m e n t o f B e r n s t e i n and H o w e l l ' s scheme [BERN69] was j u d g e d t o be an u n d e s i r a b l e c h a r a c t e r i s t i c s i n c e t h e p r o p o s e d s y s t e m i s t o o p e r a t e i n a s m a l l m a c h i n e e n v i r o n m e n t . A t u n d e r 1500 w o r d s f o r t o t a l s o f t w a r e ( i n c l u d i n g d i c t i o n a r y ) t h e a u t h o r ' s s y s t e m i s m i c r o -c o m p u t e r c o m p a t i b l e . l " 6) M i l l e r l i m i t e d c h a r a c t e r s i z e t o -j- [ M I L L 6 9 ] . S i n c e h a n d p r i n t e d c h a r a c t e r s i z e i s n o t c o n s t a n t i n a p r a c t i c a l e n v i r o n m e n t , s u c h a c o n s t r a i n t was j u d g e d u n f a v o r a b l e . The a u t h o r ' s s y s t e m i s i n s e n s i t i v e t o c h a r a c t e r s i z e . 7) M i l l e r chose t o p o s t p o n e a n a l y s i s u n t i l d a t a a q u i s i t i o n was c o m p l e t e . I n t h e a u t h o r ' s s y s t e m t h e s e two p r o c e d u r e s a r e p e r f o r m e d c o n c u r r e n t l y , t h u s m a k i n g e f f i c i e n t use o f f r e e CPU t i m e d u r i n g d a t a i n p u t and a t the same t i m e r e d u c i n g t h e r e c o g n i t i o n d e c i s i o n d e l a y ( i . e . i m p r o v i n g s y s t e m r e s p o n s e ) . 8) I n L e d e e n ' s s cheme , u s e r s h a d t o e n t e r s e v e r a l c o p i e s o f e a c h member o f t h e c h a r a c t e r r e p e r t o i r e b e f o r e c l a s s i f i c a t i o n d e c i s i o n s c o u l d be made [LEDE73] . T h i s method o f s y s t e m d i c t i o n a r y d e f i n i t i o n , i s u n d e s i r a b l e e s p e c i a l l y i n a "many u s e r " e n v i r o n m e n t . 9) C h i l i , l i k e many r e s e a r c h e r s i n t h e f i e l d o f c h a r a c t e r r e c o g n i t i o n , s e l e c t e d a pen and t a b l e t as i n p u t d e v i c e f o r h i s s y s t e m [ C H U I 7 6 ] . U n f o r t u n a t e l y , t h i s c o n s t r a i n s t h e w r i t i n g medium t o a s i n g l e s h e e t o f p a p e r p l a c e d on a h a r d s u r f a c e . S i n c e a t a b l e t i s n o t r e q u i r e d i n t h e p r o p o s e d s y s t e m , u s e r s a r e f r e e t o use a v a r i e t y o f s u i t a b l e s u r f a c e s . F u r t h e r m o r e , r e s t r i c t i o n s a r e n o t p l a c e d on c h a r a c t e r s i z e m a k i n g t h e e n v i r o n m e n t a l l t h e more a c c e p t a b l e . 106 10) A l t h o u g h t h e q u a n t i t y o f t e s t s p e r f o r m e d by C h u i i s q u i t e a c c e p t a b l e t h e q u a l i t y o f h i s a n a l y s i s c o u l d have been i m p r o v e d . I n a t t e m p t i n g t o a v o i d t h i s s h o r t c o m i n g , t h e s t a t i s t i c a l s i g n i f i c a n c e o f c o n c l u s i o n s drawn f r o m e x p e r i m e n t a l r e s u l t s was c a l c u l a t e d i n c a s e s where s a m p l e s i z e a l l o w e d t h i s . 11) S i n c e d i c t i o n a r y s e a r c h e s a r e o f t e n f a i r l y c o m p l i c a t e d , t h e number o f n e c e s s a r y r e f e r e n c e s s h o u l d u s u a l l y be m i n i m i z e d . U n l i k e C r a n e and S a v o i e [CRAN77] t h e a u t h o r p e r f o r m s many s i m p l e p r e - p r o c e s s i n g c a l c u l a t i o n s t o r e d u c e t h e amount o f d a t a t h a t i s u l t i m a t e l y p a s s e d t o t h e c l a s s i f i c a t i o n s t a g e . 12) C r a n e and S a v o i e p u b l i s h e d an i n t e r e s t i n g s y s t e m d e s c r i p t i o n b u t n e g l e c t e d t o q u a n t i f y i m p o r t a n t e x p e r i m e n t a l r e s u l t s . I n t h i s t h e s i s , s u b s t a n t i a l e f f o r t was made t o c o n d u c t m e a n i n g f u l e x p e r i m e n t s and t o f u l l y r e p o r t s u b s e q u e n t r e s u l t s . I n summary, a l l 10 f a v o u r a b l e c h a r a c t e r i s t i c s w e r e i n c l u d e d and a l l 12 u n d e s i r a b l e c h a r a c t e r i s t i c s have been e l i m i n a t e d f r o m t h e p r o p o s e d s c h e m e . The X e b e c p e n - b a s e d s y s t e m i s n o t , h o w e v e r , w i t h o u t f a u l t . I n t h e n e x t s e c t i o n s a number o f p r o b l e m s a r e d i s c u s s e d and a b r i e f c o m p a r i s o n i s made w i t h c o m p e t i t i v e s y s t e m s . 5 . 3 S y s t e m L i m i t a t i o n s The i n h e r e n t s i m p l i c i t y o f t he f e a t u r e e x t r a c t i o n s t a g e c a n l e a d t o u n a v o i d a b l e d i f f i c u l t i e s i n d i s c r i m i n a t i n g amongst c e r t a i n c h a r a c t e r g r o u p s . F o r example the r e q u e s t t h a t z e r o be drawn as an o e r s t e d ( o r t e c h n i c a l z e r o ) i s n o t m e r e l y an a e s t h e t i c f a c t o r . W i t h o u t t h e s e c o n d ( d i a g o n a l ) s t r o k e i t w o u l d be i m p o s s i b l e t o d i s t i n g u i s h i t f r o m a s i x . 107 I n F i g . 5 . 1 ( a ) , d i r e c t i o n codes f o r t h e f a m i l i a r z e r o , t h e t e c h n i c a l z e r o and d i g i t s i x a r e i n d i c a t e d . The n e c e s s i t y f o r t h e o e r s t e d i s a p p a r e n t . A s i m i l a r p r o b l e m c o u l d o c c u r f o r t h e d i g i t p a i r s i x and n i n e . I l l u s t r a t i o n s i n F i g u r e 5 . 1 ( b ) i n d i c a t e how t h e d i r e c t i o n code f o r a n i n e w i t h a l o o p ( w h i c h i s n o t a l w a y s v i s i b l e s i n c e p r e s s u r e s and n o t p e n -m o t i o n g e n e r a t e d i r e c t i o n c o d e s ) may be m i s t a k e n f o r a n o n - n o m i n a l s i x . S i n c e the ANSI n i n e does n o t e x h i b i t t he l o o p t h i s was n o t a s e r i o u s p r o b l e m when t e s t i n g w i t h t h e s t a n d a r d s e t . I t i s o b v i o u s , h o w e v e r , t h a t l o c a l v a r i a t i o n s o f some c h a r a c t e r s c a n n o t be t o l e r a t e d s i n c e t h e y e n c r o a c h upon t h e d i r e c t i o n code d e s c r i p t i o n o f o t h e r s . A s e c o n d p o s s i b l e l i m i t a t i o n o f t h e p r o p o s e d s y s t e m c o n c e r n s t h e c h o s e n d i c t i o n a r y c o n f i g u r a t i o n . N o n - t e c h n i c a l u s e r s c a n n e i t h e r m o d i f y t h e r e c o g n i t i o n l o g i c f o r e x i s t i n g s y m b o l s n o r add new s y m b o l s t o t h e s y s t e m ' s r e p e r t o i r e . H a d an e x a c t - m a t c h d i c t i o n a r y a p p r o a c h b e e n s e l e c t e d , a l e a r n i n g - t y p e p r o g r a m c o u l d have been w r i t t e n t o e x t r a c t d e f i n e d f e a t u r e s o f t h e unknown c h a r a c t e r , w h i c h c o u l d have t h e n been, a u t o m a t i c a l l y b u i l t i n t o t h e d i c t i o n a r y and r e f e r e n c e d when n e c e s s a r y . T h i s added c o n v e n i e n c e w o u l d be o f f s e t , h o w e v e r , b y i n c r e a s e d c o m p u t i n g r e q u i r e m e n t s . 5 . 4 P e r f o r m a n c e C o m p a r i s o n w i t h P u b l i s h e d S y s t e m s D e s p i t e p o t e n t i a l d i f f i c u l t i e s t h e X e b e c p e n - b a s e d s y s t e m r e m a i n s c o m p e t i t i v e w i t h e x i s t i n g s c h e m e s . Two m a j o r c r i t e r i a f o r j u d g i n g t h e s u c c e s s o f any s y s t e m a r e r e c o g n i t i o n r a t e and r e s p o n s e t i m e . I n many c a s e s , i n c r e a s i n g one d e c r e a s e s t h e o t h e r . F o r e x a m p l e , L i n r e p o r t s a h i g h r e c o g n i t i o n s c o r e o f 99.4% b u t a t t h e e x p e n s e o f a l e n g t h y 4 s e c o n d r e s p o n s e t i m e [ L I N 7 4 ] . G r o n e r ' s D i f f e r e n t i a t i n g the Zero, Oersted, and Six Familiar Zero LDRULQ (Nominal) Oersted LDRULODQ (Nominal) Six LDRULQ (Nominal) D i f f e r e n t i a t i n g the Six and Nine Figure 5.1 109 scheme, on t h e o t h e r h a n d , r e s p o n d s " q u i c k l y " b u t s u b j e c t s t e s t e d a f t e r a h a l f - h o u r t r a i n i n g s e s s i o n were n o t a b l e t o o b t a i n b e t t e r t h a n an 87% p e r f o r m a n c e [GRON66] . A l s o t he l a t t e r u t i l i z e d a l a r g e I B M S y s t e m / 3 6 0 and h i s a n a l y s i s / c l a s s i f i c a t i o n s y s t e m a l o n e r e q u i r e d more t h a n 2400 3 2 - b i t w o r d s o f c o d e . The a u t h o r ' s s y s t e m r e q u i r e s o n l y 1500 1 6 - b i t w o r d s f o r t h e e n t i r e p r o g r a m ( i n c l u d i n g a q u i s i t i o n , a l l s t a g e s o f a n a l y s i s and t h e d i c t i o n a r y ) . I n a d d i t i o n , i t r e s p o n d s a l m o s t i m m e d i a t e l y w i t h p e r f o r m a n c e l e v e l s , w e l l above 90% f o r i n e x p e r i e n c e d u s e r s h a v i n g p r a c t i c e d f o r h a l f an h o u r o r l e s s . F u r t h e r m o r e , t h e X e b e c p e n - b a s e d s y s t e m i s l e s s s p a c e - c o n s u m i n g , more n a t u r a l and p o t e n t i a l l y l e s s e x p e n s i v e t h a n most o t h e r s y s t e m s . One o f t he b e t t e r s m a l l mach ine e n v i r o n m e n t schemes a p p e a r s t o be t h a t p r o p o s e d by C h u i who r e p o r t s an o v e r a l l c h a r a c t e r r e c o g n i t i o n a c c u r a c y o f 98 .3% [Chui76] . The a u t h o r ' s s y s t e m compares f a v o r a b l y w i t h i t s l o w r e s p o n s e t i m e and a r e c o g n i t i o n a c c u r a c y above 96% t h a t i n c r e a s e s as t h e u s e r becomes p r o g r e s s i v e l y more f a i m i l i a r w i t h p e n o p e r a t i o n . C h u i ' s Computek p e n and t a b l e t c o n s t r a i n s u s e r s t o a w r i t i n g a r e a w h i c h i s e v e n s m a l l e r t h a n t h e t a b l e t a r e a s i n c e t h e s y s t e m s u f f e r s n o n -l i n e a r i t y e f f e c t s a t w r i t i n g medium e x t r e m e s . The w r i t i n g s u r f a c e (pad o f p a p e r , e t c . ) c a n n o t be p o s i t i o n e d more t h a n ^ " f rom t h e t a b l e t s u r f a c e when w r i t i n g . T h i s r e s t r i c t i o n s e v e r e l y l i m i t s t h e t y p e o f h a r d - c o p y medium a l l o w e d . The computek pen i t s e l f i s awkward and h e a v y . A 3 - o u n c e v e r t i c a l p r e s s u r e must be a p p l i e d b e f o r e p o s i t i o n a l d a t a i s commun ica t ed t o the h o s t p r o c e s s o r . I n C h u i ' s t h e s i s , h e n o t e d t h a t p a r t i a l o r e n t i r e s t r o k e s were o f t e n o m i t t e d due t o i n s u f f i c i e n t p r e s s u r e . T h i s i s e s p e c i a l l y t r u e f o r l i g h t w r i t e r s . U n d e r t h e a u t h o r ' s s y s t e m the v e r t i c a l t h r e s h o l d i s s o f t w a r e ' c o n t r o l l a b l e and i s i n c l u d e d as a p a r a m e t e r i n t h e p e r s o n a l i z e d s c h e m e . 3 C h u i s t a t e d t h a t c h a r a c t e r s l e s s t h a n t a l l w e r e d rawn w i t h o 3 d i f f i c u l t y . G r o n e r , i n h i s i m p l e m e n t a t i o n , u s e d c o d i n g f o r m s w i t h — " h i g h f o r m a t t i n g s q u a r e s and c l a i m e d t h a t t h e s e were o f a f a i r l y t y p i c a l s i z e . 1 The X e b e c p e n p e r f o r m s w e l l w i t h l e s s t h a n - j ^ " h i g h c h a r a c t e r s . C h u i c h o s e t o u t i l i z e s e v e r a l c l a s s i f i c a t i o n m e t h o d s . P o w e r s a g r e e d w i t h t h i s c o n c e p t o f m u l t i - l e v e l r e c o g n i t i o n and s u g g e s t e d u s i n g d i r e c t i o n i n f o r m a t i o n i n c o n j u n c t i o n w i t h a n o t h e r p a r a m e t e r such as r e l a t i v e p o s i t i o n [POWE73] . A l t e r n a t i v e l y , P o w e r s a d v i s e d u s i n g one p a r a m e t e r f o r r a p i d " f r o n t e n d " d e c i s i o n s o f unambiguous c h a r a c t e r s and l e a v i n g s u c c e s s i v e , p e r h a p s more c o m p l e x , t e c h n i q u e s f o r c a s e s o f l o w d i s c r i m i n a t i o n . N e i t h e r o f t h e s e s u g g e s t i o n s w e r e i m p l e m e n t e d i n t h e a u t h o r s ' s y s t e m s i n c e a d e q u a t e r e s u l t s w e r e o b t a i n e d w i t h t h e s i n g l e e x t r a c t e d f e a t u r e , p e n d i r e c t i o n . A l t h o u g h a number o f h a n d p r i n t e d c h a r a c t e r r e c o g n i t i o n s y s t e m s a p p e a r t o e x c e l i n c e r t a i n a r e a s , t h e a u t h o r does n o t know o f any t h a t i s g e n e r a l l y s u p e r i o r t o t h e one p r o p o s e d i n t h i s t h e s i s . 5.5 Recommenda t ions f o r F u r t h e r R e s e a r c h B e f o r e d i s c u s s i o n changes i n r e c o g n i t i o n s y s t e m p h i l o s o p h y t h a t m i g h t b e a p p l i e d t o i m p r o v e p e r f o r m a n c e , a number o f h a r d w a r e m o d i f i c a t i o n s t h a t w o u l d a s s i s t t h e u s e r , e s p e c i a l l y d u r i n g t h e e a r l y s t a g e s o f f a m i l i a r i z a t i o n , s h a l l be e x a m i n e d . H a n d - s i z e v a r i e s b u t p e n b a r r e l shape i s f i x e d . U s e r s w i t h p a r t i -c u l a r l y l a r g e hands f o u n d t h a t when h o l d i n g the p e n c o m f o r t a b l y , t h e p e n - t i p s t o o d above ( r a t h e r t h a n i n c o n t a c t w i t h ) the w r i t i n g s u r f a c e . I n t h i s e x t r e m e s i t u a t i o n the u s e r f u n c t i o n s i n an e n v i r o n m e n t t h a t i s n o t c o m p l e t e l y n a t u r a l t o h i m . A s i m p l e s o l u t i o n w o u l d be to p r o v i d e f o r a d j u s t m e n t o f I l l t he b a r r e l / p e n - t i p a n g l e . A n o t h e r method o f c o n s t r a i n i n g u s e r s t o h o l d t h e pen i n a n o m i n a l l y v e r t i c a l p o s i t i o n w o u l d be t o c o n f i g u r e a t r a i n g u l a r c r o s s - s e c t i o n ( o f t h e b a r r e l ) n e a r t h e pen b a s e . I n t h i s way t h e pen w o u l d be more l i k e l y t o a d o p t t h e d e s i r e d p o s t u r e . A l t e r n a t i v e l y , one m i g h t p r e f e r an i n v e r t e d b a s k e t -l i k e d e v i c e t h a t w o u l d a t t a c h j u s t above t h e p e n - t i p a l l o w i n g up and down pen m o t i o n ' w h i l e p r e v e n t i n g t i l t i n g movements . H o w e v e r , t he a u t h o r i s n o t i n agreement w i t h u s i n g s u c h a d e v i c e s i n c e the s y s t e m w o u l d t h e n be l e s s n a t u r a l t h a n a c o n v e n t i o n a l p e n / p a p e r e n v i r o n m e n t . A f i n a l s u g g e s t i o n f o r e n s u r i n g good p e n p o s t u r e c a l l s f o r t h e p l a c e m e n t o f a s m a l l b u b b l e - l e v e l above t h e s t r a i n - g u a g e a r r a y . Damped 5 " c i r c u l a r l e v e l s m e a s u r i n g l e s s t h a n — i n d i a m e t e r a r e commonly a v a i l a b l e . 16 P e n a t t i t u d e w o u l d be c o n s t a n t l y m o n i t o r e d and a l t h o u g h an e x p e r i e n c e d u s e r w o u l d n o t n e e d any a s s i s t a n c e t h e n o v i c e c o u l d b e n e f i t by v e r i f y i n g pen p o s t u r e b e f o r e f o r m i n g e a c h c h a r a c t e r . D u r i n g e x p e r i m e n t s c o n d u c t e d t h e a u t h o r p l a y e d an a c t i v e p a r t i n t h e s u b j e c t s ' l e a r n i n g p r o c e s s by a d v i s i n g when t h e pen had d e v i a t e d f r o m t h e v e r t i c a l p o s i t i o n » The b u b b l e - l e v e l c o u l d p l a y a s i m i l a r r o l e i f a c o m m e r i c a l s y s t e m were t o be d e v e l o p e d . The p r e s e n t s y s t e m f u n c t i o n s a d e q u a t e l y unde r t h e d e f i n e d 1 9 -s y m b o l s p e c i a l c h a r a c t e r s e t . B u t wha t w o u l d be t h e e f f e c t on r e c o g n i t i o n p e r f o r m a n c e and on s y s t e m r e s p o n s e t i m e i f t h e s e t were e x t e n d e d f u r t h e r o r r e d e f i n e d c o m p l e t e l y ? I n any e x t e n s i o n to t h i s w o r k , i t w o u l d be w o r t h w h i l e t o examine t r a d e - o f f s t h a t w o u l d a r i s e as r e p e r t o i r e s i z e i s i n c r e a s e d . 112 C o n s t r u c t i n g p e r s o n a l i z e d d i c t i o n a r i e s / s y s t e m s p r o v i d e d i n s i g h t i n t o t h e e f f e c t o f v a r i o u s f a c t o r s upon r e c o g n i t i o n p e r f o r m a n c e . By a s s u m i n g s y s t e m p a r a m e t e r s t o be i n d e p e n d e n t o f one a n o t h e r . . i t was p o s s i b l e t o c o n c l u d e t h a t a l t h o u g h most p a r a m e t e r s w e r e r o b u s t , s e v e r a l d i d , i n e x t r e m e c a s e s , e x e r c i s e some c o n t r o l upon p e r f o r m a n c e l e v e l s . W h i l e e a c h o f t h e s e f a c t o r s ( e . g . , d r a g p r e s s u r e t h r e s h o l d and sample r a t e ) can be o p t i m i z e d i n d e p e n d e n t l y i n c o n d u c t i n g r e p e t i t i v e t e s t i n g t r i a l s , i t i s n o t c l e a r how t h e y a f f e c t one a n o t h e r when r e - i n t r o d u c e d i n t o t h e s y s t e m . I t w o u l d be u s e f u l t o examine t h e s e i n t e r - d e p e n d e n c e s . The r e a s o n s f o r and e f f e c t s o f h y s t e r e s i s were e x p l a i n e d i n . C h a p t e r I I I ; a p o t e n t i a l d i s a d v a n t a g e i s e x a m i n e d h e r e . C o n s i d e r t h e two d i g i t s i n F i g . 5.2. When t h e h y s t e r e s i s c o n c e p t i s a p p l i e d , an i n f e r r e d minimum l e f t s t r o k e e x c e e d i n g 53° i s r e q u i r e d t o p r o d u c e an " L " i n t h e d i r e c t i o n - c o d e v e c t o r . W i t h o u t h y s t e r e s i s , any d i r e c t i o n e x c e e d i n g 45° w o u l d be s u f f i c i e n t . A l t h o u g h t h i s p o i n t may seem i n s i g n i f i c a n t a f i n i t e number o f s t r o k e s w i l l be m i s r e c o g n i z e d b e c a u s e o f i t . W r i t e r s who c a r e l e s s l y f o r m t h e i r s t r o k e s a r e p a r t i c u l a r l y s u s c e p t i b l e . To what e x t e n t h y s t e r e s i s e f f e c t s a i d o r h i n d e r t h e a v e r a g e u s e r can o n l y be a s c e r t a i n e d t h r o u g h f u r t h e r s u b j e c t t e s t i n g . G = 55 : Acceptable with 0 = 53 : Acceptable without or without but unacceptable hysteresis. with h y s t e r e s i s . Figure 5.2 Negative E f f e c t s of Hysteresis 113 P a r t i c i p a n t s i n r e c o g n i t i o n t r a i l s o f t e n a sked wha t w o u l d happen i f one was t o d raw a c h a r a c t e r 9 0 ° o r 1 8 0 ° r o t a t e d . They w e r e t o l d t h a t t h e s y s t e m c o u l d accomoda te r o t a t i o n s o f up t o a p p r o x i m a t e l y 4 5 ° and t h a t g r e a t e r r o t a t i o n s c o u l d be t o l e r a t e d i f t h e u s e r was w e l l aware o f pen m e c h a n i c s ( r e f e r t o A p p e n d i x B ) . B u t r o t a t i o n s c o u l d a l s o b e t o l e r a t e d b y r o t a t i n g t h e q u a d r a n t p l a n e i t s e l f . I n t h e e v e n t o f an "Unknown" i n p u t t h e d i r e c t i o n -code v e c t o r w i t h e a c h e l e m e n t a l d i r e c t i o n r o t a t e d ( i . e . , m o d u l o - 4 i n c r e m e n t e d o r d e c r e m e n t e d ) c o u l d be r e t e s t e d . I t w o u l d o n l y be w o r t h w h i l e i m p l e m e n t i n g s u c h a scheme i f t h e c u r r e n t p a t t e r n a n a l y s i s t e c h n i q u e s w e r e changed s i n c e as t h e s y s t e m s t a n d s v e r y few "Unknown" i n p u t d e c i s i o n s a r e r e n d e r e d ( c f . T a b l e s V I I I and I X . f o r q u a n t i t i a t i v e r e s u l t s ) . The f r e e d o m t h e d e s i g n e r has i n d e f i n i n g t h e c h a r a c t e r r e p e r t o i r e i s l i k e l y to h a v e a p r o n o u n c e d (and p o s i t i v e ) e f f e c t upon r e c o g n i t i o n p e r f o r m a n c e . I t r e m a i n s unknown , h o w e v e r , t o what e x t e n t t h e s y s t e m w o u l d s u f f e r i f t h i s f r e e d o m was removed ( i . e . , i f s y m b o l s were t o t a l l y d e f i n e d a p r i o r i ) . R e s u l t s o b t a i n e d i n t h i s t h e s i s a r e e n c o u r a g i n g and i t w o u l d be w o r t h w h i l e t o d e t e r m i n e w h e t h e r e v e n l a r g e r c h a r a c t e r s e t s c o u l d be accommodated u s i n g o n l y i n f e r r e d d i r e c t i o n s f o r t h e i r d e s c r i p t i o n . T h i s l a s t r emark i s e s p e c i a l l y t r u e i n t h e c a s e o f p e r s o n a l i z e d s y s t e m s . P o w e r s s u g g e s t e d t h a t h a v i n g b o t h p o s i t i o n a l and d i r e c t i o n a l i n f o r m a t i o n a t o n e ' s d i s p o s a l w o u l d i m p r o v e p e r f o r m a n c e c o n s i d e r a b l y [POWE73] . T h i s may r e q u i r e a t a b l e t d e v i c e and a m a j o r a d v a n t a g e s o f t h e X e b e c pen w o u l d be l o s t . A p r e f e r a b l e a p p r o a c h m i g h t be t o f u r t h e r e x a m i n e the p r o p e r t i e s o f t h e f o r c e i n f o r m a t i o n g e n e r a t e d a t t h e p e n - t i p . I t was n o t e d e a r l i e r t h a t t o t h e a u t h o r ' s k n o w l e d g e w r i t i n g v e l o c i t y w a s f a i r l y 114 u n p r e d i c t a b l e d i f f e r i n g f rom day t o d a y , u s e r t o u s e r , s y m b o l t o s y m b o l and e v e n w i t h i n a g i v e n s y m b o l . R e s e a r c h i n t h i s a r e a m i g h t u l t i m a t e l y p r o v i d e a s o l u t i o n t o the p r o b l e m o f s p u r i o u s d i r e c t i o n i n f o r m a t i o n . I n t h e c a s e o f t h e ambiguous p a i r , d i g i t s s i x and n i n e o f F i g . . 5 . 1 ( b ) , i t i s p r o b a b l y r e a s o n a b l e t o assume t h a t t h e " L " i n t h e l o o p o f t h e n i n e i s s h o r t e r - l i v e d t h a n t h e f i n a l " l " s t r o k e o f t h e s i x and t h a t t h e two d i g i t s c o u l d be d i f f e r e n t i a t e d by d i c a r d i n g a l l s h o r t - l i v e d d i r e c t i o n s . The u n d e r l y i n g a s s u m p t i o n i s t h a t pen v e l o c i t y i s c o n s t a n t , i . e . s h o r t - l i v e d i m p l i e s s m a l l d i s p l a c e m e n t . T h i s a s s u m p t i o n , i f p rove 'd g e n e r a l l y t r u e , c o u l d l e a d t h e way t o a s e c o n d a r y l e v e l o f c h a r a c t e r c l a s s i f i c a t i o n . R a t h e r t h a n d e f i n e an a b s o l u t e d i r e c t i o n d u r a t i o n t h r e s h o l d , one c o u l d compare l e n g t h s o f s u c c e s s i v e ( o r s u s p e c t ) d i r e c t i o n s h y p o t h e s i z i n g t h a t n o n - s i g n i f i c a n t l o o p s and l o c a l v a r i a t i o n s a r e o f s h o r t e r d u r a t i o n t h a n n o m i n a l s t r o k e s . A g a i n , t h i s i d e a w o u l d have t o be s u b s t a n t i a t e d by f u r t h e r e x p e r i m e n t a t i o n . I n t e r - c h a r a c t e r s e g m e n t a t i o n o r d e l i m i t a t i o n was n o t c o n s i d e r e d i n t h e p r o p o s e d i m p l e m e n t a t i o n b u t w o u l d be i m p o r t a n t i n a n o n -l a b o r a t o r y a p p l i c a t i o n s i n c e h a v i n g t o w a i t f o r " p r o m p t s " w o u l d d e t r a c t t h e u s e r f r o m h i s p r i m a r y i n t e r e s t . A number o f schemes have b e e n a p p l i e d i n t h e p a s t . One o f t h e s i m p l e s t t o imp lemen t i n v o l v e s d e t e r m i n i n g t h e g e o m e t r i c a l e x t e n t o f a s t r o k e . By d e f i n i n g a s t r o k e ' s p h y s i c a l s p a c e and v e r i f y i n g t h a t s u c c e s s i v e s t r o k e s l i e i n t h i s s p a c e , i t i s p o s s i b l e t o e s t i m a t e w h e t h e r o r n o t s t r o k e s a r e f r o m a common c h a r a c t e r . T h i s scheme i s n o t p r e s e n t l y a p p l i c a b l e t o t h e a u t h o r ' s s y s t e m s i n c e p o s i t i o n a l i n f o r m a t i o n i s n o t a v a i l a b l e . 115 A s e c o n d p o s s i b i l i t y c o n c e r n s the t i m e e l a p s e d b e t w e e n s u c c e s s i v e s t r o k e s ; i . e . , a l e n g t h y i n t e r v a l s u g g e s t s a c o m p l e t e d s y m b o l . G r o n e r found t h a t 0 . 3 s e c o n d s was o p t i m a l f o r e x p e r i e n c e d u s e r s [GRON66] . U s i n g t h i s t e c h n i q u e , u s e r s a r e f o r c e d t o r e d u c e t h e i r n o r m a l h a n d w r i t i n g s p e e d by a p p r o x i m a t e l y 50%. A more e l e g a n t a p p r o a c h w o u l d be t o d e t e r m i n e w h e t h e r t h e s u b s e q u e n t s t r o k e c o u l d r e a s o n a b l y be an e l e m e n t o f t h e p r e v i o u s f o r m a t i o n . I f n o t , t h e s t r o k e must be t h e f i r s t o f t h e s u b s e q u e n t s y m b o l and a d e c i s i o n r e g a r d i n g t h e p r e v i o u s s y m b o l c o u l d be communica t ed t o t h e u s e r . C r a n e and S a v o i e h a v e i m p l e m e n t e d s u c h a scheme b u t do n o t r e m a r k a s t o i t s e f f e c t i v e n e s s [ C R A N 7 6 ] . i n u s i n g t h i s t e c h n i q u e t h e u s e r i s n e i t h e r c o n s t r a i n e d t o f i x e d c h a r a c t e r s i z e s ( a s i n g e o m e t r i c d e l i m i t a t i o n ) n o r t o r e d u c i n g h i s w r i t i n g s p e e d ( d a t a may be e n t e r e d i n s h o r t b u r s t s and commands c a n be c o n c a t e n a t e d ) . A d d i t i o n a l t i m e and c o r e a r e r e q u i r e d a t t he d i c t i o n a r y c r e a t i o n s t a g e . R e s e a r c h t o d e t e r m i n e w h e t h e r t h e a d d i t i o n a l e f f o r t i s j u s t i f i e d w o u l d be w o r t h w h i l e . A s a f i n a l r e c o m m e n d a t i o n one c o u l d c o n s i d e r t h e p o s s i b i l i t y o f t i m e - s h a r i n g p e r s o n a l i z e d s y s t e m s f o r s e v e r a l u s e r s . Such an i m p l e m e n t a t i o n m i g h t be u s e f u l i n an e d u c a t i o n a l e n v i r o n m e n t where s t u d e n t s use t h e pens t o answer q u e s t i o n s i n w o r k b o o k s a t t h e i r d e s k s and t e a c h e r s m o n i t o r t h e i r p r o g r e s s a t a m a i n c o n s o l e . S i m i l a r l y t he p e n m i g h t f i n d a p p l i c a t i o n i n a c o m m e r i c a l e n v i r o n m e n t where u s e r s e n t e r d a t a ( n u m e r i c a l or o t h e r ) a s t h e n e e d a r i s e s . A g a i n , a p e n c o u l d be i n s t a l l e d at e a c h d e s k and t h e s u b s y s t e m p e r s o n a l i z e d f o r e a c h o f t he o p e r a t o r s . A s t u d y o f t h e c o m p u t i n g power r e q u i r e d s h o u l d be u n d e r t a k e n . 116 5 .5 C o n c l u s i o n s A s i m p l e , e f f e c t i v e , c o r e - e f f i c e n t and n a t u r a l r e a l - t i m e scheme o p e r a t i n g i n a l i m i t e d e n v i r o n m e n t was d e s i g n e d and i m p l e m e n t e d t o a c c u r a t e l y r e c o g n i z e h a n d p r i n t e d s y m b o l s o f a l m o s t any s i z e and any r e a s o n a b l e d e g r e e o f s l a n t and d i s t o r t i o n . R e s u l t s i n d i c a t e t h a t d r a g - f o r c e i n f o r m a t i o n a l o n e i s s u f f i c i e n t t o c h a r a c t e r i z e s y m b o l s o f t h e d e f i n e d n u m e r i c s p l u s g e s t u r e r e p e r t o i r e u s e d i n t h i s t h e s i s . S i n c e the number o f c a l c u l a t i o n s r e q u i r e d i s f a i r l y m i n i m a l , t h e n e e d f o r e x t e n s i v e c o m p u t i n g f a c i l i t i e s i s o b v i a t e d . F u r t h e r m o r e , c o r e r e q u i r e m e n t s a r e m i c r o c o m p u t e r c o m p a t i b l e a t a p p r o x i m a t e l y .1500 16 b i t - w o r d s f o r t h e e n t i r e c o m p i l e d r e c o g n i t i o n scheme i n c l u d i n g d i c t i o n a r y . The p r o p o s e d s y s t e m i s s m a l l , i n e x p e n s i v e and i t s p e r f o r m a n c e i s v e r y c o m p e t i t i v e w i t h e x i s t i n g s c h e m e s . R e c o g n i t i o n a c c u r a c i e s e x c e e d i n g t h e g e n e r a l l y a c c e p t e d l e v e l o f 95% a r e e a s i l y a c h i e v e d and s y s t e m r e s p o n s e t i m e i s l o w due t o t h e c o n c u r r e n c y o f t h e a c q u i s i t i o n and a n a l y s i s s t a g e s and t o e f f i c i e n t a n a l y s i s t e c h n i q u e s . The p e n - p a p e r e n v i r o n m e n t i s n a t u r a l and e l i m i n a t e s t h e need f o r r e t r a n s c r i p t i o n . P e r s o n a l i z i n g ( i . e . , u s e r - d e d i c a t i n g ) t h e s y s t e m i m p r o v e s o p e r a t o r a c c e p t a n c e by r e d u c i n g i m p o s e d s t y l i s t i c c o n s t r a i n t s . I t i s w o r t h n o t i n g , h o w e v e r , t h a t c o m p a r a b l e p e r f o r m a n c e may be a t t a i n e d u n d e r a l e s s n a t u r a l , r e s t r i c t e d s y s t e m b e c a u s e o f t h e r o b u s t n e s s o f o p t i m a l p a r a m e t e r v a l u e s and b e c a u s e o f t h e s c h e m e ' s i n h e r e n t t o l e r a n c e t o u n d e f i n e d c h a r a c t e r v a r i a t i o n s . A t e c h n i q u e f o r a u t o m a t i n g t h e g e n e r a t i o n o f p e r s o n a l i z e d s y s t e m s was i m p l e m e n t e d s u c c e s s f u l l y . The ANSI h a n d p r i n t e d n u m e r i c s s e t and n i n e s p e c i a l g e s t u r e s y m b o l s w e r e t e s t e d i n a s i m u l a t e d a p p l i c a t i o n s e n v i r o n m e n t . R e s u l t s d e m o n s t r a t e d t h e i m p o r t a n c e o f s e l e c t i n g f a m i l i a r s y m b o l s w h i c h a r e s o f t w a r e d e f i n e d i n 117 t h e p r o p o s e d s y s t e m and t h e r e f o r e e a s i l y m o d i f i e d . The r e c o g n i t i o n scheme i s w e l l r e c e i v e d by n o n - t e c h n i c a l u s e r s who p e r f o r m a t l e a s t a s w e l l as t e c h n i c a l u s e r s . Such a s y s t e m r e q u i r i n g n e i t h e r s p e c i a l w r i t i n g s u r f a c e s n o r e x t e n s i v e f a c i l i t i e s and o f f e r i n g good c l a s s i f i -c a t i o n p e r f o r m a n c e w i t h l o w s y s t e m r e s p o n s e t i m e c o u l d p r o v e a u s e f u l component i n f u t u r e s y s t e m ' s d e s i g n . 118 REFERENCES [ANSI74] American National Standard Character Set for Handprinting (ANSI 43.45), ANSI, Inc., New York, 1974. [BATC74] B. Batchelor, Practical Approach to Pattern Classification, Plenum Press, London, New York, 1974 [BERN68] M. J. Bernstein, "A Method for Recognizing Handprinted Characters i n Real-Time", in Pattern Recognition, L.N. Kanal, Ed., Thompson Book Co., Washington, 1968. [BERN69] M.J. Bernstein and H. Howell, "Handprinted Input for On-Line Systems", Rep. NASA-CR-12B4, Systems Development Corp., Santa Monica, California, 1969. [CASE64] R. Casey and G. Nagy, "Recognition of Printed Chinese Characters", IEEE Trans, on Elect. Computers, Vol. C-15, No.l, pp. 750-752, December 1964. [CCI 78] "Experimental Signature Verification System Detects Forgeries", Canadian Controls & Instruments, p. 5, November 1978. [CHUI76] T.K. Chui, "Real-Time Computer Recognition of Handprinted Characters", M.A.Sc. Thesis, The University of British Columbia, 1976. [CLAR73] R. Clare, Designing Logic Systems Using State Machines, McGraw-Hill, New York, 1973. [CRAN77] H.D. Crane and R.E. Savoie, "An On-Line Data Entry System for Handprinted Characters", Computer Magazine, pp. 43-50, March 1977. 1 1 9 [DEV067] D . B . D e v o e , " A l t e r n a t i v e s to H a n d p r i n t i n g i n t h e M a n u a l E n t r y o f D a t a " , I E E E T r a n s , o f Human F a c t o r s i n E l e c t r o n i c s , V o l . 8 , N o . 1 , p p . 2 1 - 3 2 , M a r c h 1 9 6 7 . [DIM057] T . L . D i m o n d , " D e v i c e s f o r R e a d i n g H a n d - W r i t t e n C h a r a c t e r s " , P r o c . E a s t e r n J o i n t Computer C o n f e r e n c e , p p . 2 3 2 - 2 3 7 , December 1 9 5 7 . [DUDA68] R . O . D u d a , P . E . H a r t , " E x p e r i m e n t s i n t he R e c o g n i t i o n o f H a n d p r i n t e d T e x t : P a r t I I - C o n t e x t A n a l y s i s " , P r o c . F J C C , p p . 1 1 3 9 - 1 1 4 9 , 1 9 6 8 . [FRAN78] H . W . F r a n k e , Augewandte I n f o r m a t i k - A p p l i e d I n f o r m a t i c s , V o l . 1 1 , p p . 5 0 6 - 5 1 0 , 1 9 7 8 . [FREE61] H . F r e e m a n , "On t h e E n c o d i n g o f A r b i t r a r y G e o m e t r i c C o n f i g u r a t i o n s " , I E E E T r a n s , on E l e c t r o n i c C o m p u t e r s , V o l . E C - 1 0 , p p . 2 6 0 - 2 6 8 , J u n e 1 9 6 1 . [GENC68] H . G e n c h i e t a l . , " R e c o g n i t i o n o f H a n d - w r i t t e n N u m e r i c a l C h a r a c t e r s f o r A u t o m a t i c L e t t e r S o r t i n g " , P r o c . I E E E , V o l . 5 6 , p p . 1 2 9 2 - 1 3 0 1 , A u g u s t 1 9 6 8 . [GREA63] E . C . G r e a n i a s e t a l . , "The R e c o g n i t i o n o f H a n d - W r i t t e n N u m e r a l s b y C o n t o u r A n a l y s i s " , I B M J . o f R e s . and D e v . , V o l . 7 , N o . 1 , p p . 1 4 - 2 1 , J a n u a r y 1 9 6 3 . [GRON66] G . F . G r o n e r , " R e a l - T i m e R e c o g n i t i o n o f H a n d p r i n t e d T e x t " , A F I P S P r o c . F J C C , V o l . 2 9 , p p . 5 9 1 - 6 0 1 , 1 9 6 6 . [GRON68] G.F. Groner, "Real-Time Recognition of Handprinted Symbols" in Pattern Recognition, L.N. Kanal, Ed., Thompson Book Co., Washington, 1968. [HOEL62] P. Hoel, Introduction to Mathematical S t a t i s t i c s , 3rd E d i t i o n , pp. 143-145, John Wiley & Sons, New York, 1962. [HOSK72] K.H. Hosking, "A Contour Method for the Recognition of Handp r i n t e d Characters", i n Machine Perception of Patterns and P i c t u r e s , The W h i t e f r i a r s Press, Ltd,, London, 1972 . [ICHI741 T. Ichikawa and J . Yoshida, "On-Line Recognition of Handprinted Characters with Associative Read-Out of Patterns i n a Memory", Proc. of Second International J o i n t Conference on Pattern Recognition, pp. 206-207, August 1974. [ITO 78] M.R. Ito and T.K. Chui, "On-Line Computer Recognition of Proposed Standard ANSI (USASI) Handprinted Characters", Pattern Recognition, V o l . 10, pp. 341-349, 1978. [LANS70] J . Lansdown, "Computer Art f o r T h e a t r i c a l Performance", i n P r o c , ACM I n t e r n a t i o n a l Computer Symposium, Bonn, 1979. [LANS78] J . Lansdown, "The Computer i n Choreography", Computer Magazine, V o l . 11, No. 8, pp. 19-31, August 1978. [LEDE73] K.S. Ledeen, see,"The Ledeen Character Recognizer", i n P r i n c i p l e s  of I n t e r a c t i v e Graphics, W.M. Newman and R.F. S p r o u l l , McGraw-Hill, Inc., New York, 1973. 121 [ L E V I 6 9 ] M . D . L e v i n e , " F e a t u r e C l a s s i f i c a t i o n : A S u r v e y " , P r o c . o f I E E E , V o l . 5 7 , p p . 1 3 9 1 - 1 4 0 5 , A u g u s t 1 9 6 9 . [ L I N 74] W . C . L i n and T . L . S c u l l y , "Computer I d e n t i f i c a t i o n o f C o n s t r a i n e d H a n d p r i n t e d C h a r a c t e r s w i t h a H i g h R e c o g n i t i o n R a t e " , I E E E T r a n s , on S y s t e m s , M a n , and C y b e r n e t i c s , V o l . S M C - 4 , N o . 6 , p p . 497-504, November 1 9 7 4 . [ M I L L 6 9 ] G . M i l l e r , " O n - L i n e R e c o g n i t i o n o f H a n d - G e n e r a t e d S y m b o l s " , A F I P S P r o c . F J C C , V o l . 3 5 , p p . 3 9 9 - 4 1 2 , 1 9 6 9 . [NAGY68] G . N a g y , " S t a t e o f t h e A r t i n P a t t e r n R e c o g n i t i o n " , P r o c . I E E E , V o l . 5 6 , N o . 5 , p p . 8 3 6 - 8 6 2 , May 1 9 6 8 . [P0WE70] V . M . P o w e r s , " O n - L i n e R e c o g n i t i o n o f Hand-Drawn C h a r a c t e r s f r o m D i r e c t i o n a l I n f o r m a t i o n " , P h . D . d i s s e r t a t i o n , U n i v e r s i t y o f M i c h i g a n , 1 9 7 0 , [POWE73] V . M . P o w e r s , " P e n - D i r e c t i o n Sequences i n C h a r a c t e r R e c o g n i t i o n , P a t t e r n R e c o g n i t i o n , V o l . 5 , p p . 2 9 1 - 3 0 2 , December 1 9 7 3 . [ S P I E 7 5 ] M . R . S p i e g e l , " P r o b a b i l i t y and S t a t i s t i c s , McGraw H i l l Book C o . , San F r a n c i s c o , 1 9 7 5 . [STAL75] W. S t a l l i n g s , "Compu te r D e s c r i p t i o n and R e c o g n i t i o n o f P r i n t e d C h i n e s e C h a r a c t e r s " , A F I P S P r o c . F J C C , V o l . 4 4 , p p . 1 0 1 5 - 1 0 2 5 , 1 9 7 5 . [SUEN79] C Y . S u e n , " H a n d w r i t i n g M o d e l s i n C a n a d i a n E d u c a t i o n " , I n t e r i m R e p o r t f r o m C o n c o r d i a U n i v e r s i t y , M o n t r e a l , M a r c h 1 9 7 9 . [ T E I T 6 4 ] W. T e i t , " R e a l - T i m e R e c o g n i t i o n o f H a n d - D r a w n C h a r a c t e r s " , A F I P S . P r o c . F J C C , V o l . 2 6 , p a r t I , p p . 5 5 9 - 5 7 5 , 1 9 6 4 . 122 [TOU 72] J . T . Tou and R . C . G o n z a l e s , " R e c o g n i t i o n o f H a n d - W r i t t e n C h a r a c t e r s by T o p o l o g i c a l F e a t u r e E x t r a c t i o n and M u l t i l e v e l C a t e g o r i z a t i o n " , I E E E T r a n s , on C o m p u t e r s , V o l . C - 2 1 , p p . 7 7 6 - 7 8 5 , J u l y 1 9 7 2 . [TRUA78] B . T r u a x , "Compute r M u s i c C o m p o s i t i o n : The P o l y p h o n i c POD S y s t e m " , Computer M a g a z i n e , V o l . 1 1 , N o . 8 , p p . 1 9 - 3 1 , A u g u s t 1 9 7 8 . [WONN72] T . H . and R . J . W o n n a c o t t , I n t r o d u c t o r y S t a t i s t i c s , p . 2 2 1 , 2nd E d i t i o n , J o h n W i l e y & S o n s , T o r o n t o , 1 9 7 2 . [WOOD76] J . Wood, 6 t h C o n g r e s s o f t h e I n t e r n a t i o n a l E r g o n o m i c s A s s o c i a t i o n , U n i v e r s i t y o f M d . , C o l l e g e P a r k , J u l y 1 1 - 1 6 , 1 9 7 6 . APPENDIX A Example of Recognition System Performance (Digits c i r c l e d were i n c o r r e c t l y c l a s s i f i e d , o v e r a l l performance exceeds 98%) t ~ 3 7 1 r 5" C V ? U7 4 ^ °J ^ ^ A x / ~ ^ ^ 9 - C5 - VO 1 ^ ^ s> H 1 124 APPENDIX B Example of Distorted Character Forms APPENDIX C 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0094674/manifest

Comment

Related Items