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A comparison of Pan and zoom and rubber sheet navigation Nekrasovski, Dmitry 2006

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A Comparison of Pan and Zoom and Rubber Sheet Navigation by  Dmitry  Nekrasovski  B . C . S . , C a r l e t o n U n i v e r s i t y , 2000  A THESIS SUBMITTED  IN P A R T I A L F U L F I L M E N T O F  THE REQUIREMENTS  F O RT H E D E G R E E O F  M a s t e r of Science in The  F a c u l t y of G r a d u a t e Studies (Computer  The  Science)  University O f British C o l u m b i a J a n u a r y 2006 ©  D m i t r y Nekrasovski  2006  ii  Abstract A s i n f o r m a t i o n v i s u a l i z a t i o n t o o l s a r c used l o v i s u a l i z e d a t a s e t s o f i n c r e a s i n g size, t h e r e is a g r o w i n g n e e d for t e c h n i q u e s t h a t f a c i l i t a t e efficient  navigation.  P a n a n d z o o m n a v i g a t i o n e n a b l e s users to d i s p l a y a r e a s o f i n t e r e s t at different resolutions.  Fbcus+contexl  t e c h n i q u e s a i m to o v e r c o m e t h e d r a w b a c k s o f p a n  a n d z o o m b y d y n a m i c a l l y i n t e g r a t i n g areas o f i n t e r e s t a n d c o n t e x t  regions.  To  d a t e , e m p i r i c a l c o m p a r i s o n s o f t h e s e two n a v i g a t i o n p a r a d i g m s h a v e b e e n l i m i t e d in scope a n d inconclusive. In two c o n t r o l l e d s t u d i e s ,  we evaluated  navigation techniques  t i v e o f t h e p a n a n d z o o m a n d focus (-context a p p r o a c h e s , cus-(-context  'the  representa-  p a r t i c u l a r fo-  t e c h n i q u e e x a m i n e d was r u b b e r sheet n a v i g a t i o n , i m p l e m e n t e d i n  a w a y that a f f o r d e d a set  o f n a v i g a t i o n a c t i o n s s i m i l a r to p a n a n d z o o m  navi-  g a t i o n . T h e t w o t e c h n i q u e s w e r e used b y 10 s u b j e c t s i n e a c h s t u d y t o p e r f o r m a navigation-intensive  task  in a large tree d a t a s e t .  effect o f t h e a m o u n t o f s c r e e n r e a l estate d e v o t e d navigation technique. affected  Study  1 investigated  to c o n t e x t  the  r e g i o n s for e a c h  P e r f o r m a n c e w i t h b o t h t e c h n i q u e s was not  by this factor, b u t was influenced b y technique-specific  significantly strategies de-  S t u d y 2 c o m p a r e d the p e r f o r m a n c e o f t h e t w o  techniques.  P a n a n d z o o m n a v i g a t i o n was f o u n d to be f a s t e r t h a n r u b b e r sheet  navigation  veloped by subjects.  a n d was r a t e d by s u b j e c t s  as easier a n d less m e n t a l l y d e m a n d i n g .  We  discuss  t h e i m p l i c a t i o n s o f t h e s e r e s u l t s , i n c l u d i n g the r e l a t i o n s h i p b e t w e e n n a v i g a t i o n t e c h n i q u e , t a s k , a n d user s t r a t e g y , a n d p r o p o s e d i r e c t i o n s for f u l u r e w o r k .  Contents Abstract  ii  Contents  iii  List of Tables  vi  vii  List of Figures  Acknowledgements  1  2  3  ix  Introduction  1  1.1  Motivation  1  1.2  Overview  2  Related Work  7  2.1  Pan and Zoom Navigation (PZN)  7  2.2  R u b b e r Sheet N a v i g a t i o n ( R S N )  9  2.3  Guaranteed Visibility  2.4  Evaluation of Navigation Techniques  2.5  Evaluation of Tree Visualizations  Task and Dataset 3.1  13  :  -.  14 17  \  .  19  Task  19  Determining  the  lowest  3.1.1  T a s k 1:  c o m m o n ancestor  20  3.1.2  T a s k 2: D e t e r m i n i n g t h e t o p o l o g i c a l d i s t a n c e b e t w e e n n o d e s  21  3.1.3  T a s k 3: D e t e r m i n i n g w h e t h e r t w o s u b t r e e s a r e a d j a c e n t  21  .  Contents 3.1.4  iv  T a s k 4: D e t e r m i n i n g w h e t h e r a s u b t r e e c o n t a i n s u n m a r k e d nodes  3.2  4  5  2  2  2  3  2  5  Dataset  Study 1 4.1  Hypotheses  4.2  ^  2  Interfaces  2  6  4.2.1  Navigation  2  9  4.2.2  Overviews and Foci  4.2.3  G u a r a n t e e d V i s i b i l i t y a n d Levels of C o n t e x t  30  4.2.4  R S N - N o O V Interface  34  4.2.5  P Z N - N o O V Interface  34  4.2.6  R S N + O V Interface  35  4.2.7  P Z N + O V Interface  35  •  30  4.3  Task and Dataset  36  4.4  Apparatus  36  4.5  Participants  4.6  Design  37  4.7  Procedure . . :  38  4.8  Measures  39  4.9  Results  4.10  :  •  36  4  0  S u m m a r y of Results  4  2  4.11  Strategies  4  5  4.12  Discussion  4  6  4  9  4  9  5  0  Study 2 5.1  Hypotheses  5.2  Interfaces  5.3  T a s k a n d Dataset  5.4  Apparatus  54  5.5  Participants  5  :  ">  n  4  Contents  6  v  5.6  Design  54  5.7  Procedure  55  5.8  Measures  57  5.9  Results  57  5.10 Summary of Results  61  5.11 Discussion  61  Conclusions and Future W o r k  64  Bibliography  67  A  S t u d y 1 T r a i n i n g P r o t o c o l .'  74  B  Study 2 Training Protocol  81  C  Study 1 Questionnaires  90  D  Study 2 Questionnaires  110  vi  List of Tables 4.1  Interface c o m b i n a t i o n s e x a m i n e d in S t u d i e s 1 a n d 2  4.2  Latin  square u s e d  25  t o c o u n t e r b a l a n c e the o r d e r o f p r e s e n t a t i o n for  level o f c o n t e x t i n S t u d y 1  37  4.3  Levels of c o n t e x t used in S t u d y 1  38  4.4  Results of A N O V A s  41  4.5  Navigation  5.1  M e a n s a n d effects o f n a v i g a t i o n t e c h n i q u e i n S t u d y 2  o f level o f c o n t e x t b y i n t e r f a c e i n S t u d y 1 . .  strategies  developed by subjects in S t u d y 1  46  59  vii  List of Figures 1.1  Pan and zoom navigation ( P Z N )  3  1.2  R u b b e r sheet, n a v i g a t i o n ( R S N )  3  2.1  P a n n i n g m e t a p h o r s e x a m i n e d by J o h n s o n  8  2.2  Rubber  2.3  R u b b e r sheet, n a v i g a t i o n w i t h p o l y g o n a l s t r e t c h i n g  11  2.4  R u b b e r sheet n a v i g a t i o n in T r e e J u x t a p o s e r  12  2.5  G u a r a n t e e d v i s i b i l i t y i n C i t y L i g h t s [51]  15  2.6  G u a r a n t e e d v i s i b i l i t y in p a n a n d z o o m i n t e r f a c e s  15  3.1  T a s k 1: D e t e r m i n i n g t h e lowest c o m m o n a n c e s t o r ( L C A )  20  3.2  T a s k 2: D e t e r m i n i n g t h e t o p o l o g i c a l d i s t a n c e b e t w e e n n o d e s .  3.3  T a s k 3: D e t e r m i n i n g w h e t h e r  3.4  T a s k 4: D e t e r m i n i n g w h e t h e r a s u b t r e e c o n t a i n s u n m a r k e d n o d e s .  22  4.1  S t u d y 1 R S N - N o O V interface  27  4.2  S t u d y 1 P Z N - N o O V interface  27  4.3  Study 1 R S N + O V interface  28  4.4  S t u d y 1 P Z N + O V interface  28  4.5  M o t i v a t i n g s c e n a r i o for u s e o f m u l t i p l e foci i n S t u d y 1  31  4.6  C a l c u l a t i o n o f levels .of context, in S t u d y 1 R S N interfaces  . . . .  33  4.7  C a l c u l a t i o n o f levels o f c o n t e x t in S t u d y 1 P Z N i n t e r f a c e s  . . . .  33  4.8  M e a n p e r - t r i a l c o m p l e t i o n times by interface in S t u d y 1  sheet n a v i g a t i o n with  orthogonal stretching  two s u b t r e e s a r e a d j a c e n t .  11  . .  21  . . . . .  22  41  List  4.9  Mean  per-trial  of Figures  completion  times  and  viii  trend line  for  the R S N -  N o O V interface 4.10  Mean  per-trial  43 completion  times  and  t r e n d l i n e for t h e P Z N -  N o O V interface 4.11  43  M e a n p e r - t r i a l c o m p l e t i o n t i m e s a n d t r e n d l i n e for t h e  RSN+OV  interface 4.12  44  M e a n p e r - t r i a l c o m p l e t i o n t i m e s a n d t r e n d l i n e for t h e  PZN+OV  interface  44  5.1  S t u d y 2 R S N - N o O V interface  5.2  S t u d y 2 P Z N - N o O V interface  51  5.3  S t u d y 2 R S N + O V interface  52  5.4  S t u d y 2 P Z N + O V interface  52  5.5  C a l c u l a t i o n o f levels o f c o n t e x t i n S t u d y 2 R S N i n t e r f a c e s  . . . .  53  5.6  C a l c u l a t i o n o f levels o f c o n t e x t  . . . .  53  5.7  M e a n p e r - t r i a l c o m p l e t i o n times b y interface in S t u d y 2  5.8  M e a n per-trial completion times by navigation technique and by block  . . . !  in S t u d y 2 P Z N interfaces  51  58  60  ix  Acknowledgements R e s e a r c h is a l w a y s a c o l l a b o r a t i v e p r o c e s s ,  a n d t h i s t h e s i s is n o e x c e p t i o n .  I  w o u l d like t o t h a n k a l l t h e p e o p l e w h o h a v e h e l p e d m e i n m a k i n g it h a p p e n . M y supervisors, J o a n n a M c G r e n e r e and T a m a r a M u n z n e r , provided copious a m o u n t s o f a d v i c e , g u i d a n c e , a n d s u p p o r t t h r o u g h o u t t h i s p r o j e c t . It h a s  been  a fantastic l e a r n i n g experience a n d a real pleasure to w o r k w i t h b o t h o f t h e m .  Adam in  litis  B o d n a r collaborated with me on most aspects of the work described  thesis. H i s  hard  work, creative ideas, a n d ready wit have been  to the success o f this p r o j e c t (and the p r e s e r v a t i o n of m y  essential  sanity!)  F r a n g o i s G u i m b r e t i e r e c o m m i t t e d a g r e a t d e a l o f t i m e to h e l p s h a p e a n d d i r e c t t h i s w o r k . H i s e x p e r t a d v i c e a n d a t t e n t i o n to d e t a i l h a v e p r o v e n i n v a l u a b l e . K a r o n M a c l e a n somehow  f o u n d t i m e t o a c t as s e c o n d r e a d e r for t h i s t h e s i s  a m o n g all her o t h e r c o m m i t m e n t s .  H e r h e l p f u l i n p u t is g r e a t l y a p p r e c i a t e d .  M a n y other p e o p l e c o n t r i b u t e d to this work in a variety of ways. M o t i v a t i o n for t h e s t u d i e s c a m e David  from discussions  Hillis, W a y n e M a d d i s o n , and  with phylogenetic  members  biologists,  especially  of their research groups.  Early-  feedback was p r o v i d e d by P a t r i c k B a u d i s c h , B e n B e d e r s o n , J e a n - D a n i e l Fekete. C a t h e r i n e Plaisant. and K a t h e r i n e St. J o h n . Later on. study design and analysis was influenced b y conversations w i t h L e a h F i n d l a t e r , H e i d i L a m . B a r r y P o . a n d M e l a n i e T o r y , w h i l e J a m e s S l a c k a s s i s t e d w i t h i m p l e m e n t a t i o n issues. M e m b e r s of the  Imager,  M U X , a n d H C T labs h e l p e d  out  as p i l o t s t u d y  subjects  and  c r e a t e d a s t i m u l a t i n g a n d f u n e n v i r o n m e n t for c o n d u c t i n g t h i s r e s e a r c h . L a s t b u t m o s t c e r t a i n l y not least. J u l i e L a v o i e a n d m y parents, Sofia N e k r a s o v s k i , h a v e g i v e n m e b o u n d l e s s T h i s is for y o u .  love a n d c o n s t a n t  Alex and  encouragement.  i  Chapter 1  Introduction 1.1  Motivation  I n f o r m a t i o n v i s u a l i z a t i o n uses c o m p u t e r - s u p p o r t e d i n t e r a c t i v e v i s u a l r e p r e s e n t a t i o n s o f a b s t r a c t d a t a t o a i d c o g n i t i o n [13].  Information visualization  n i q u e s a r e n o w b e i n g a p p l i e d t o fields s u c h as p h y l o g e n e t i c  tech-  b i o l o g y , w h i c h is  c o n c e r n e d w i t h d i s c o v e r i n g e v o l u t i o n a r y r e l a t i o n s h i p s b e t w e e n species, a n d req u i r e s i n c r e a s i n g l y s o p h i s t i c a t e d v i s u a l i z a t i o n t o o l s for t h i s p u r p o s e .  A s infor-  m a t i o n v i s u a l i z a t i o n t o o l s a r e u s e d t o v i s u a l i z e d a t a s e t s o f i n c r e a s e d size a n d c o m p l e x i t y , t h e r e is a g r o w i n g n e e d for t e c h n i q u e s t h a t f a c i l i t a t e r a p i d a n d efficient n a v i g a t i o n in such datasets. T w o p r i m a r y a p p r o a c h e s have b e e n p r o p o s e d in the i n f o r m a t i o n v i s u a l i z a t i o n literature to enable such n a v i g a t i o n . P a n  zoom navigation operations ent  ( P Z N ) [24] relies o n a c o m b i n a t i o n o f p a n n i n g a n d z o o m i n g  t o e n a b l e u s e r s t o v i e w d i s c r e t e p o r t i o n s o f t h e d a t a s e t at  resolutions.  and  P a n a n d z o o m navigation techniques  overview windows  to p r o v i d e users w i t h c o n t e x t u a l  eas o u t s i d e t h e r e g i o n o f c u r r e n t interest.  are often  differ-  paired with  i n f o r m a t i o n a b o u t ar-  However, overview windows take u p  s c r e e n r e a l e s t a t e a n d m a y n o t p r o v i d e e n o u g h r e s o l u t i o n to c l e a r l y i d e n t i f y feat u r e s o f interest.  Focus-f context ( F + C )  navigation techniques  [11]  combine  h i g h - r e s o l u t i o n d i s p l a y s o f a r e a s o f i n t e r e s t t o t h e user (focus r e g i o n s ) a n d c o n t e x t u a l i n f o r m a t i o n a b o u t t h e rest o f t h e d a t a s e t ( c o n t e x t r e g i o n s ) i n t o a s i n g l e unified view.  In o r d e r t o a c c o m p l i s h t h i s w i t h o u t s a c r i f i c i n g s c r e e n r e a l e s t a t e ,  m a n y f o c u s + c o n t e x t interfaces rely o n d i s t o r t i o n to d y n a m i c a l l y integrate focus and  c o n t e x t r e g i o n s as users n a v i g a t e t h r o u g h t h e d a t a s e t .  Some  researchers  Chapter  1.  Introduction  2  h a v e s u g g e s t e d t h a t f o c u s + c o n t e x t t e c h n i q u e s m a y a l s o b e n e f i t f r o m t h e use of o v e r v i e w w i n d o w s [5]. T h e r e h a s b e e n n o c o n s e n s u s i n t h e l i t e r a t u r e as t o w h i c h a p p r o a c h is s u p e r i o r , a n d s o m e r e s e a r c h e r s h a v e s u g g e s t e d t h a t t h e i r r e l a t i v e effectiveness is h i g h l y d e p e n d e n t  o n t h e p a r t i c u l a r n a v i g a t i o n t a s k for w h i c h  t h e y a r e u s e d [22, 25]. The  relative performance of p a n a n d z o o m a n d focus+context  techniques c a n b e influenced b y a variety o f factors.  navigation  T h e s e include the type of  d a t a s e t b e i n g n a v i g a t e d a n d its v i s u a l r e p r e s e n t a t i o n , t h e n a t u r e a n d l e v e l o f difficulty of t h e navigation task, the interactions afforded b y t h e n a v i g a t i o n techniques, a n d t h e fraction of screen real estate allotted t o context regions,  whether  integrated w i t h focus regions o r presented i n a separate overview w i n d o w . l a s t f a c t o r is r e f e r r e d t o i n t h i s t h e s i s as l e v e l o f c o n t e x t .  This  T h e dataset types  that most c o m m o n l y motivate research i n the area o f n a v i g a t i o n i n the i n f o r m a t i o n visualization literature d u e t o their use i n a variety o f a p p l i c a t i o n d o m a i n s include textual documents  [5, 25], m a p s  [22, 24], a n d g r a p h s , e s p e c i a l l y  tree  s t r u c t u r e s [30, 43]. A v a r i e t y o f n a v i g a t i o n t a s k s c a n b e p e r f o r m e d w i t h e a c h o f these dataset types. E x a m p l e s i n c l u d e v i s u a l search, b r o w s i n g , c o m p a r i s o n , a n d m o r e c o m p l e x c o m p o u n d tasks c o m p r i s e d o f m u l t i p l e instances o f these tasks. One  c a t e g o r y o f t a s k t h a t m a y b e p a r t i c u l a r l y s u i t a b l e for a s s e s s i n g p e r f o r m a n c e  of n a v i g a t i o n t e c h n i q u e s d u e t o t h e i r p o t e n t i a l for r e q u i r i n g s i g n i f i c a n t of  n a v i g a t i o n is t a s k s t h a t i n v o l v e u n d e r s t a n d i n g t h e t o p o l o g y  amounts  of a g r a p h o r  tree structure. T h e interactions afforded b y variants o n the p a n a n d z o o m a n d f o c u s + c o n t e x t n a v i g a t i o n m e t a p h o r s often include some or a l l of p a n n i n g , z o o m ing  i n , a n d z o o m i n g out, all of which c a n be implemented i n a variety of ways  d e p e n d i n g o n t h e design goals a n d i n t e n d e d dataset of a p a r t i c u l a r n a v i g a t i o n technique.  L e v e l o f c o n t e x t affects t h e a m o u n t o f c o n t e x t u a l i n f o r m a t i o n a v a i l -  a b l e t o users d u r i n g n a v i g a t i o n , a n d m a y r e m a i n s t a t i c o r c h a n g e d y n a m i c a l l y d e p e n d i n g o n user interactions. In  recent y e a r s , e m p i r i c a l e v a l u a t i o n h a s g a i n e d i n c r e a s e d p r o m i n e n c e i n  i n f o r m a t i o n v i s u a l i z a t i o n l i t e r a t u r e [16]. R e c e n t l y p u b l i s h e d u s e r s t u d i e s h a v e e v a l u a t e d c o m m e r c i a l l y a v a i l a b l e v i s u a l i z a t i o n t o o l s [30], c o m p a r e d t h e u s a b i l i t y  Chapter  1.  Introduction  3  of different v i s u a l i z a t i o n t e c h n i q u e s for s p e c i f i c t a s k s [25], a n d e x a m i n e d p a t t e r n s a s s o c i a t e d w i t h t h e use o f v i s u a l i z a t i o n t o o l s i n t h e field [34]. A n u m b e r o f t h e s e s t u d i e s h a v e e i t h e r c o m p a r e d t h e p e r f o r m a n c e o f different n a v i g a t i o n t e c h niques o r e x a m i n e d interfaces w i t h a n d w i t h o u t a n overview b a s e d o n t h e same navigation technique.  However, these investigations have t y p i c a l l y i n v o l v e d a  relatively narrow subset of variations o n t h e p a n a n d z o o m a n d focus+context p a r a d i g m s , as w e l l as differences i n v i s u a l r e p r e s e n t a t i o n a n d i n t e r a c t i o n s afforded b y interfaces u s i n g each of t h e two types o f n a v i g a t i o n , m a k i n g s t u d y r e s u l t s difficult t o i n t e r p r e t . F u r t h e r m o r e , t h e d a t a s e t s a n d t a s k s u s e d i n m o s t of t h e s e s t u d i e s h a v e b e e n d e v i s e d s p e c i f i c a l l y for s t u d y p u r p o s e s , w i t h o u t r e g a r d to t h e needs o f users i n a p a r t i c u l a r d o m a i n , a n d n o s t u d y has e v a l u a t e d n a v i g a t i o n t e c h n i q u e a n d p r e s e n c e o f o v e r v i e w as o r t h o g o n a l f a c t o r s .  Finally,  t o d a t e l e v e l o f c o n t e x t h a s n o t b e e n e x a m i n e d as a f a c t o r i n e m p i r i c a l s t u d i e s of  navigation techniques.  T h e w o r k d e s c r i b e d i n t h i s thesis r e p r e s e n t s a  first  a t t e m p t t o fill t h e s e g a p s i n t h e l i t e r a t u r e .  1.2  Overview  T h i s t h e s i s d e s c r i b e s e x p e r i m e n t s p e r f o r m e d t o q u a n t i t a t i v e l y e v a l u a t e t h e effect o f n a v i g a t i o n t e c h n i q u e ( p a n a n d z o o m v s .  focus+context),  presence o r  a b s e n c e o f a n o v e r v i e w , a n d l e v e l o f c o n t e x t o n user p e r f o r m a n c e a n d s a t i s f a c tion. W e chose t o specifically e x a m i n e presence o r absence of overview a n d level of c o n t e x t d u e t o t h e l a c k o f e m p i r i c a l r e s u l t s c o n c e r n i n g t h e r e l a t i v e i n f l u e n c e o f these factors o n p e r f o r m a n c e w i t h each of t h e two n a v i g a t i o n m e t a p h o r s . T h e specific f o c u s + c o n t e x t  navigation  t e c h n i q u e t h a t w e chose t o e v a l u a t e is r u b b e r  sheet  ( R S N ) [45], w h i c h a l l o w s u s e r s t o s t r e t c h o r s q u i s h f o c u s a r e a s as  t h o u g h t h e d a t a s e t w a s l a i d o u t o n a r u b b e r sheet w i t h i t s b o r d e r s n a i l e d d o w n . The  differences b e t w e e n t h e t w o n a v i g a t i o n t e c h n i q u e s u s e d i n o u r e x p e r i m e n t s  are  i l l u s t r a t e d i n F i g u r e s 1.1 a n d 1.2. W h i l e a z o o m a c t i o n i n P Z N c a u s e s a r e a s  o u t s i d e t h e s e l e c t e d r e g i o n o f i n t e r e s t t o m o v e off-screen, t h e e q u i v a l e n t o p e r a t i o n i n R S N c a u s e s t h e s e a r e a s t o b e c o m p r e s s e d a r o u n d t h e edges o f t h e v i e w  Chapter  F i g u r e 1.1:  1.  Introduction  4  S e l e c t i n g (left) a n d result of z o o m i n g i n t o ( r i g h t ) a r e c t i l i n e a r r e g i o n  with pan and zoom navigation.  A r e a s o u t s i d e t h e z o o m e d r e g i o n are p u s h e d  off-screen.  1  F i g u r e 1.2:  S e l e c t i n g (left) a n d result of z o o m i n g i n t o ( r i g h t ) a r e c t i l i n e a r r e g i o n  w i t h r u b b e r sheet n a v i g a t i o n . A r e a s o u t s i d e t h e z o o m e d r e g i o n are c o m p r e s s e d a r o u n d t h e edges of the v i e w .  but remain visible. W e chose R S N as the m o s t a p p r o p r i a t e r e p r e s e n t a t i v e t e c h n i q u e b e c a u s e of the fact t h a t it is the o n l y d i s t o r t i o n - b a s e d f o c u s + c o n t e x t t e c h n i q u e t o d a t e to b e c o m b i n e d w i t h g u a r a n t e e d v i s i b i l i t y [37], a p r o p e r t y t h a t ensures t h a t regions of interest r e m a i n v i s i b l e i n d e p e n d e n t of user n a v i g a t i o n a c t i o n s . W h i l e g u a r a n t e e d v i s i b i l i t y is a r e l a t i v e l y n e w c o n c e p t i n t h e i n f o r m a t i o n v i s u a l i z a t i o n l i t e r a t u r e , a recent s t u d y [5] suggests t h a t it m a y p r o v i d e b e n e f i t s i n t e r m s of b o t h p e r f o r m a n c e a n d user preference. In a n effort to use t h e b e s t a v a i l a b l e i m p l e m e n t a t i o n s of each n a v i g a t i o n t e c h n i q u e for o u r e x p e r i m e n t , i n o u r s t u d i e s we p r o v i d e d g u a r a n t e e d v i s i b i l i t y i n interfaces u s i n g b o t h P Z N a n d R S N n a v i g a -  Chapter  5  Introduction  1.  t i o n . O u r use o f R S N w a s a l s o m o t i v a t e d b y t h i s t e c h n i q u e ' s s i m i l a r i t y t o P Z N i n t e r m s o f user i n t e r a c t i o n . O u r i m p l e m e n t a t i o n o f r u b b e r s h e e t n a v i g a t i o n was b a s e d o n t h e f r a m e w o r k o f S l a c k et a l . [47], w h i c h , l i k e P Z N i n t e r f a c e s ,  provides  m u l t i p l e levels o f m a g n i f i c a t i o n a n d a n i n t e r a c t i o n m o d e l b a s e d o n r e c t a n g u l a r selection areas.  W e were also i n t e r e s t e d i n c o m p a r i n g R S N t o P Z N b e c a u s e o f  the lack of e m p i r i c a l evaluation of the former i n the literature. A detailed discuss i o n o f r e l a t e d w o r k i n i m p l e m e n t a t i o n a n d e v a l u a t i o n issues for b o t h n a v i g a t i o n t e c h n i q u e s as w e l l as g u a r a n t e e d v i s i b i l i t y c a n b e f o u n d i n C h a p t e r 2. T h e t a s k u s e d i n o u r s t u d y is a t o p o l o g i c a l n a v i g a t i o n t a s k m o t i v a t e d b y t h e requirements of phylogenetic biologists, w h o require sophisticated  visualization  t o o l s t o s u p p o r t t h e i r w o r k . O u r d i s c u s s i o n s w i t h p h y l o g e n e t i c b i o l o g i s t s l e a d us t o d e v e l o p a set o f c o m p o u n d t o p o l o g i c a l t a s k s r e l a t e d t o t h e i r n e e d s , o f w h i c h we t h e n s e l e c t e d a n a v i g a t i o n - i n t e n s i v e t a s k s u i t a b l e for o u r c o m p a r i s o n . d a t a s e t u s e d i n o u r s t u d y is a l a r g e tree d a t a s e t a l s o d e r i v e d f r o m  The  phylogenetic  biology. W e developed abstract versions of the task a n d the dataset in order to a l l o w us t o p e r f o r m a q u a n t i t a t i v e s t u d y w i t h n o n - e x p e r t users. F u r t h e r d e t a i l s a b o u t t h e t a s k a n d d a t a s e t u s e d i n o u r s t u d i e s c a n b e f o u n d i n C h a p t e r 3. W e c o n d u c t e d two e x p e r i m e n t s , task a n d dataset.  e a c h i n v o l v i n g 40 s u b j e c t s a n d t h e  E a c h o f t h e e x p e r i m e n t s a l s o u s e d t h e s a m e f o u r interfaces,  representing all c o m b i n a t i o n s of P Z N a n d R S N w i t h a n d w i t h o u t although the  same  design of the  interfaces  was  overviews,  refined b e t w e e n t h e s t u d i e s .  The  experiments were designed to measure p e r f o r m a n c e b y r e c o r d i n g the c o m p l e t i o n times a n d n u m b e r of n a v i g a t i o n actions r e q u i r e d to p e r f o r m the task w i t h each e x p e r i m e n t a l interface.  W e also g a t h e r e d d a t a o n s e l f - r e p o r t e d m e a s u r e s  such  as p e r c e i v e d m e n t a l a n d p h y s i c a l effort, ease o f n a v i g a t i o n , a n d ease o f use. O u r first s t u d y , d i s c u s s e d i n C h a p t e r 4, r e p r e s e n t s t h e first e v a l u a t i o n o f t h e effect o f l e v e l o f c o n t e x t o n p e r f o r m a n c e w i t h different n a v i g a t i o n  techniques.  T h e r e s u l t s o f t h i s s t u d y s h o w t h a t level o f c o n t e x t d i d n o t h a v e a s i g n i f i c a n t i m p a c t o n p e r f o r m a n c e for a n y o f t h e interfaces. s t r o n g l y affected b y differences  H o w e v e r , t h e s t u d y ' s r e s u l t s were  in navigation strategies developed b y subjects  to d e a l w i t h t h e p e r c e i v e d c o m p l e x i t y o f t h e i n t e r f a c e s .  T h i s effect m o t i v a t e d u s  Chapter  1.  Introduction  6  t o s i m p l i f y t h e i n t e r f a c e s a n d d e v e l o p d e t a i l e d t r a i n i n g s t r a t e g i e s for o u r s e c o n d study. Our  s e c o n d s t u d y , d e s c r i b e d i n C h a p t e r 5, is t h e  first  to evaluate the  ef-  fects o f n a v i g a t i o n t e c h n i q u e a n d t h e p r e s e n c e o f a n o v e r v i e w as o r t h o g o n a l f a c t o r s . W e f o u n d t h a t s u b j e c t s p e r f o r m e d s i g n i f i c a n t l y faster u s i n g P Z N t h a n RSN  regardless of whether a n overview was present.  A d d i t i o n a l l y , s u b j e c t s re-  q u i r e d fewer n a v i g a t i o n i n t e r a c t i o n s a n d r e p o r t e d a lower m e n t a l effort PZN  while completing the task.  with  O u r results also i n d i c a t e t h a t overviews d i d  n o t a p p e a r t o i m p r o v e p e r f o r m a n c e , b u t were s t i l l p e r c e i v e d as b e n e f i c i a l .  We  d i s c u s s the i m p l i c a t i o n s o f t h e s e r e s u l t s , i n c l u d i n g t h e r e l a t i o n s h i p b e t w e e n n a v i g a t i o n t e c h n i q u e a n d t a s k , a n d m a k e r e c o m m e n d a t i o n s for f u t u r e e v a l u a t i o n s of R S N .  C h a p t e r 6 o u t l i n e s t h e l i m i t a t i o n s o f o u r e x p e r i m e n t s , lists s o m e p o s s i -  b i l i t i e s for f u t u r e w o r k s t e m m i n g f r o m o u r s t u d i e s , a n d c o n c l u d e s t h i s thesis. The  r e s e a r c h p r o j e c t t h a t c o m p r i s e d t h e t w o s t u d i e s d i s c u s s e d i n t h i s thesis  was c o n d u c t e d b y t h e a u t h o r j o i n t l y w i t h A d a m B o d n a r .  W i t h i n this project,  t h e a u t h o r w a s r e s p o n s i b l e for i n v e s t i g a t i n g t h e effects o f n a v i g a t i o n t e c h n i q u e , w h i l e B o d n a r i n v e s t i g a t e d t h e effects o f p r e s e n c e o r a b s e n c e o f o v e r v i e w .  This  thesis t h e r e f o r e e m p h a s i z e s t h e a s p e c t s o f t h e s t u d i e s r e l a t e d t o n a v i g a t i o n t e c h niques, while those aspects related to presence of overview are presented g r e a t e r d e t a i l i n B o d n a r ' s m a s t e r ' s thesis [12].  A s a r e s u l t , S e c t i o n s 4.3,  in 4.4,  4.5, a n d 4.8 o f C h a p t e r 4 a n d S e c t i o n s 5.3, 5.4, 5.5, a n d 5.8 o f C h a p t e r 5 a r e j o i n t l y a u t h o r e d w i t h B o d n a r , w h i l e C h a p t e r 3 is b a s e d o n a v e r s i o n j o i n t l y a u t h o r e d w i t h h i m . S u b s t a n t i a l p o r t i o n s o f t h i s thesis a l s o a p p e a r i n a p a p e r p u b l i s h e d i n t h e p r o c e e d i n g s o f t h e 2006 S I G C H I c o n f e r e n c e o n H u m a n tors in c o m p u t i n g systems,  fac-  w h i c h was j o i n t l y a u t h o r e d w i t h B o d n a r , J o a n n a  M c G r e n e r e , F r a n c o i s G u i m b r e t i e r e , a n d T a m a r a M u n z n e r [38]. T o s u m m a r i z e , t h e r e m a i n d e r o f t h i s thesis is o r g a n i z e d as follows. 2 d i s c u s s e s r e l a t e d w o r k a n d p r o v i d e s a b a c k g r o u n d for o u r s t u d i e s .  Chapter  Chapter 3  discusses the task a n d dataset used in b o t h our studies. T h e design a n d results of  e a c h e x p e r i m e n t a r e d e t a i l e d a n d d i s c u s s e d i n C h a p t e r s 4 a n d 5.  C h a p t e r 6 s u g g e s t s d i r e c t i o n s for f u t u r e w o r k a n d c o n c l u d e s t h i s thesis.  Finally,  7  Chapter 2  Related W o r k This  c h a p t e r e x a m i n e s d e s i g n issues i n p a n a n d z o o m a n d r u b b e r s h e e t n a v i g a -  tion interfaces, discusses  tations  the  c o n c e p t o f g u a r a n t e e d v i s i b i l i t y a n d its  implemen-  in g r e a t e r d e t a i l , a n d p r e s e n t s a n o v e r v i e w o f r e l e v a n t w o r k i n e m p i r i c a l  e v a l u a t i o n o f n a v i g a t i o n t e c h n i q u e s a n d tree v i s u a l i z a t i o n s .  2.1  Pan and Zoom Navigation (PZN)  In t h e c o n t e x t o f i n f o r m a t i o n v i s u a l i z a t i o n ,  navigation  c a n b e d e f i n e d as  the  t r a v e r s a l o f a n i n f o r m a t i o n s t r u c t u r e b y s e l e c t i n g p a r t s o f the c u r r e n t v i e w o f t h e s t r u c t u r e [19]. t i o n t o d a y is  T h e d o m i n a n t m e t a p h o r for n a v i g a t i o n in i n f o r m a t i o n v i s u a l i z a -  pan and zoom navigation,  w h i c h has been used in a variety o f  e x p e r i m e n t a l s y s t e m s (see s u r v e y i n H o r n b a e k . B e d e r s o n . a n d P l a i s a n t [24]). as w e l l as a n u m b e r o f c o m m e r c i a l a p p l i c a t i o n s [1  ;  c o m b i n e s two classes o f n a v i g a t i o n techniques:  p a n n i n g , w h i c h a l l o w s u s e r s to  20].  P a n and zoom  navigation  c h a n g e the visible region of the d a t a s e t t h r o u g h h o r i z o n t a l a n d v e r t i c a l t r a n s l a t i o n s , a n d z o o m i n g , w h i c h c h a n g e s t h e s c a l e a t w h i c h t h e 'dataset is v i e w e d to allow users to v i e w  regions  of interest  a t g r e a t e r o r lesser r e s o l u t i o n .  In  t h i s thesis, p a n a n d z o o m n a v i g a t i o n is u s e d t o m e a n t h e c o m b i n a t i o n o f t h e s e t w o classes o f r i g i d t w o - d i m e n s i o n a l t r a n s f o r m a t i o n s , as o p p o s e d t o  navigation  m e t h o d s t h a t a d a p t t h e s e t e c h n i q u e s for use in d i s t o r t i o n - b a s e d i n t e r f a c e s [3. 4]. A l t h o u g h p a n n i n g is o n e o f t h e most  basic techniques  for n a v i g a t i n g d a t a ,  t h e r e h a v e b e e n r e l a t i v e l y few a t t e m p t s to d e s c r i b e a n d c o m p a r e d i f f e r e n t n i n g v a r i a t i o n s . J o h n s o n [27] p r o v i d e s a s u r v e y o f t h i s l i t e r a t u r e a n d t h e f o l l o w i n g p a n n i n g m e t a p h o r s , i l l u s t r a t e d i n F i g u r e 2.1:  pan-  describes  Chapter 2. Related Work  Push Background  Push Camera  F i g u r e 2.1:  8  Touch Edge Camera  P a n n i n g m e t a p h o r s e x a m i n e d b y J o h n s o n [27].  1. P u s h b a c k g r o u n d : T o v i e w a n off-screen r e g i o n , u s e r s p a n i n t h e d i r e c t i o n o p p o s i t e t o w h e r e t h i s r e g i o n lies, a s t h o u g h m o v i n g t h e b a c k g r o u n d of the v i s u a l i z a t i o n .  2.  P u s h c a m e r a : T o v i e w a n off-screen r e g i o n , u s e r s p a n i n t h e d i r e c t i o n t h i s r e g i o n lies, as t h o u g h m a n i p u l a t i n g a c a m e r a t h a t is v i e w i n g t h e d a t a s e t .  3. T o u c h e d g e c a m e r a : T o v i e w a n off-screen r e g i o n , users t o u c h t h e e d g e o f t h e v i e w in t h e d i r e c t i o n t h i s r e g i o n lies.  J o h n s o n c o m p a r e d these three m e t a p h o r s  in, a c o n t r o l l e d s t u d y  performed  on a touch display. Results showed that P u s h B a c k g r o u n d p a n n i n g was superior to t h e o t h e r k i n d s o f p a n n i n g i n t e r m s o f b o t h p e r f o r m a n c e a n d u s e r Consistent  with  t h i s f i n d i n g , w e use t h e P u s h  implementation of pan and zoom  preference.  Background metaphor  in o u r  navigation.  A variety o f z o o m i n g navigation approaches have been described in the information visualization literature.  T h e s e p r i m a r i l y differ i n t e r m s o f h o w t h e  s c a l e o f o b j e c t s i n t h e d a t a s e t is m a n i p u l a t e d z o o m out actions.  H o r n b a e k et a l .  as u s e r s p e r f o r m z o o m  [24] d e s c r i b e  in a n d  the following approaches  to  i m p l e m e n t i n g z o o m i n g in t e r m s o f s c a l e c h a n g e s :  1. G e o m e t r i c z o o m i n g :  T h e most, c o m m o n a p p r o a c h , w h e r e t h e a p p a r e n t  size o f o b j e c t s i n c r e a s e s l i n e a r l y w h e n u s e r s z o o m i n t o a n a r e a o f i n t e r e s t , and  d e c r e a s e s at t h e s a m e r a t e w h e n t h e y z o o m o u t .  Chapter 2. Related Work  9  2. S e m a n t i c z o o m i n g : I n t r o d u c e d i n P e r l i n a n d F o x ' s P a d s y s t e m [40], t h i s a p p r o a c h reveals n e w f e a t u r e s i n a d d i t i o n t o i n c r e a s i n g t h e size o f e x i s t i n g ones as users z o o m i n . T h i s t e c h n i q u e is p a r t i c u l a r l y s u i t a b l e for m a p d a t a s e t s , where users a r e o f t e n i n t e r e s t e d i n different  k i n d s o f features  d e p e n d i n g o n the scale a t w h i c h t h e y a r e v i e w i n g t h e d a t a . 3. C o n s t a n t d e n s i t y z o o m i n g :  T h i s a p p r o a c h , first used b y W o o d r u f f ,  L a n d a y . a n d S t o n e b r e a k e r [50], uses a m o r e c o m p l e x r e l a t i o n s h i p b e t w e e n scale a n d a p p e a r a n c e , w h e r e a c o n s t a n t n u m b e r o f o b j e c t s is v i s i b l e r e gardless of zooming actions.  T o d a t e , n o s t u d y has c o m p a r e d these three a p p r o a c h e s t o d e t e r m i n e w h e t h e r s e m a n t i c o r c o n s t a n t d e n s i t y z o o m i n g offer b e n e f i t s c o m p a r e d t o s i m p l e g e o m e t ric z o o m i n g . T h e implementation of pan and z o o m navigation discussed in this thesis t h e r e f o r e relies o n g e o m e t r i c z o o m i n g for c o n s i s t e n c y w i t h t h e m a j o r i t y of t h e s y s t e m s d o c u m e n t e d i n t h e l i t e r a t u r e . T w o m a i n a p p r o a c h e s for i m p l e m e n t i n g scale c h a n g e s d u r i n g z o o m n a v i g a t i o n a c t i o n s h a v e been d e s c r i b e d .  I n j u m p z o o m i n g [40], c h a n g e s of scale  occur instantaneously, w i t h o u t intermediate steps, while in a n i m a t e d z o o m i n g [8], t h e t r a n s i t i o n f r o m t h e o l d t o t h e n e w s c a l e is s m o o t h l y a n i m a t e d . A s t u d y b y B e d e r s o n a n d B o l t m a n [7] c o m p a r e d these t w o m e t h o d s i n a t o p o l o g y r e c a l l t a s k . A l t h o u g h no difference i n c o m p l e t i o n t i m e w a s f o u n d , results i n d i c a t e d that, t h e users p r o d u c e d topology r e c o n s t r u c t i o n s o f h i g h e r q u a l i t y w i t h a n i m a t e d z o o m i n g . B a s e d o n t h i s r e s u l t , we use s m o o t h a n i m a t e d t r a n s i t i o n s during z o o m navigation actions in o u r implementation of pan a n d z o o m .  2.2  R u b b e r Sheet N a v i g a t i o n ( R S N )  A s p r e v i o u s l y m e n t i o n e d , t h e m a j o r a l t e r n a t i v e to p a n a n d z o o m n a v i g a t i o n is t h e f o c u s - f - c o n t e x t a p p r o a c h , first i n t r o d u c e d b y S p e n c e a n d A p p e r l e y [48]. U n l i k e p a n a n d z o o m i n t e r f a c e s , w h i c h e i t h e r o n l y present, users w i t h regions of c u r r e n t i n t e r e s t o r p r o v i d e c o n t e x t u a l i n f o r m a t i o n  in a s e p a r a t e o v e r v i e w  Chapter 2. Related Work window, focus+context a s i n g l e v i e w [11].  techniques  10  integrate focus regions a n d c o n t e x t  T h r o u g h this integration, the focus+context  within  approach aims  to r e d u c e t h e c o g n i t i v e l o a d r e q u i r e d for u s e r s t o m a i n t a i n a g l o b a l r e p r e s e n t a t i o n o f the dataset  a n d t h e i r n a v i g a t i o n a l h i s t o r y [33].  Most  focus+context  interfaces in the l i t e r a t u r e integrate focus a n d c o n t e x t regions using d y n a m i c a l l y chosen distortions. E x a m p l e s of such  distortion-based  t e c h n i q u e s i n c l u d e fish-  e y e v i e w s [18 44]. h y p e r b o l i c g e o m e t r y [31], n o n l i n e a r m a g n i f i c a t i o n [29] ;  n u m b e r o f o t h e r a p p r o a c h e s [35].  Other focus+context  ;  and a  approaches that do not  r e l y o n d i s t o r t i o n i n c l u d e a g g r e g a t i n g c o n t e x t r e g i o n s i n t o g l y p h s [14. 43] a n d s h o w i n g c o n t e x t u a l i n f o r m a t i o n t h r o u g h l a y e r s o f l e n s e s [10].  T h e evaluation  d i s c u s s e d i n t h i s t h e s i s is i n t e n d e d to b e p r i m a r i l y r e l e v a n t t o t h e l i t e r a t u r e o n distortion-based focus+context the t e r m "focus+context" The is  thesis  is u s e d to refer s p e c i f i c a l l y t o t h e s e i n t e r f a c e s .  particular focus+context  r u b b e r sheet n a v i g a t i o n ,  and  i n t e r f a c e s , a n d in t h e r e m a i n d e r o f t h i s  n a v i g a t i o n technique e x a m i n e d in this thesis  originally developed by Sarkar. Snibbe. Tversky.  R e i s s [45]. T h e n a m e o f t h i s t e c h n i q u e c o m e s f r o m its c e n t r a l m e t a p h o r o f  i n t e r a c t i n g w i t h t h e d a t a s e t as t h o u g h it were l a i d o u t o n a r u b b e r sheet w i t h its b o r d e r s t a c k e d d o w n . U s e r s c a n select a n d s t r e t c h o r c o m p r e s s a r b i t r a r y a r e a s o f t h e r u b b e r sheet, w h i l e t h e rest o f t h e r u b b e r s h e e t r e m a i n s v i s i b l e , t h o u g h it m a y b e c o m p r e s s e d .  T h i s approach h a s t h e a d v a n t a g e o f p r e s e r v i n g u s e r s '  sense o f l o c a t i o n in t h e d a t a s e t . w h i c h c a n e a s i l y b e lost d u r i n g d i s t o r t i o n - b a s e d n a v i g a t i o n [30]. With  S a r k a r et a l . d e s c r i b e two v a r i a n t s o f r u b b e r sheet n a v i g a t i o n .  orthogonal stretching,  i l l u s t r a t e d i n F i g u r e 2.2. u s e r s are r e s t r i c t e d to  s e l e c t i n g v e r t i c a l o r h o r i z o n t a l slices o f t h e dataset. a r e a s , w h i c h a r e s t r e t c h e d out. w i t h o u t a f f e c t i n g t h e rest o f the dataset. T h i s h a s t h e a d v a n t a g e o f preserving o r t h o g o n a l o r d e r i n g o f p o i n t s in t h e d a t a s e t . b u t suffers f r o m d i s c o n t i n u i t y o f s c a l e at the b o u n d a r y b e t w e e n focus a n d c o n t e x t a r e a s .  ing,  s h o w n in F i g u r e 2.3.  enables  Polygonal stretch-  users to select a r b i t r a r y p o l y g o n s as  areas  of interest, and s m o o t h l y integrates stretched out focus areas w i t h c o n t e x t regions in t e r m s of scale. symmetry.  However, p o l y g o n a l s t r e t c h i n g does not preserve d a t a s e t  Chapter 2. Related Work  F i g u r e 2.2:  R u b b e r sheet n a v i g a t i o n w i t h o r t h o g o n a l  S a r k a r et a l . [45].  The  symmetry  stretching as  11  d e s c r i b e d in  o f the d a t a s e t is p r e s e r v e d at t h e e x p e n s e o f  d i s c o n t i n u i t i e s o f scale.  F i g u r e 2.3:  R u b b e r sheet n a v i g a t i o n w i t h p o l y g o n a l s t r e t c h i n g u s i n g a r e c t a n -  g u l a r selection  a r e a as d e s c r i b e d i n S a r k a r et a l . [45].  F o c u s a n d context, a r e a s  a r e s m o o t h l y i n t e g r a t e d , b u t d a t a s e t s y m m e t r y is not p r e s e r v e d .  Chapter 2. Related Work  12  T h e p a r t i c u l a r v e r s i o n o f r u b b e r sheet n a v i g a t i o n d i s c u s s e d  i n this  thesis  is b a s e d o n t h a t i m p l e m e n t e d i n t h e T r e e J u x t a p o s e r v i s u a l i z a t i o n t o o l d e v e l oped by Munzner, 2.4).  Guimbretiere, Taziran, Zhang,  and Zhou  [37]  (see  T h e f o r m o f r u b b e r sheet n a v i g a t i o n u s e d i n T r e e J u x t a p o s e r  Figure  represents  a m i d d l e g r o u n d b e t w e e n o r t h o g o n a l a n d p o l y g o n a l s t r e t c h i n g as d e s c r i b e d b y S a r k a r et a l .  [45], since it p r o v i d e s s m o o t h i n t e g r a t i o n o f focus a n d c o n t e x t  regions w h i l e p r e s e r v i n g s y m m e t r y o f tree s t r u c t u r e s . S i m i l a r l y t o m a n y i m p l e m e n t a t i o n s o f p a n a n d z o o m n a v i g a t i o n , T r e e J u x t a p o s e r uses r e c t i l i n e a r r e g i o n s as s e l e c t i o n a r e a s , a n d p r o v i d e s a n i m a t e d t r a n s i t i o n s t o m a i n t a i n user c o n t e x t during stretching.  T h e s e s i m i l a r i t i e s e n a b l e a n easier c o m p a r i s o n b e t w e e n t h e  two t y p e s o f n a v i g a t i o n File  Find  Tools  SKneliai  techniques. Help  arthlacanihuci'phala  |li«t.rfcv«<t Uiaryx  hulot rntrui  duloi M M U M lift y I itoi.iirs myriprislis  amnion •  _ [ acanthopterygti osteiththyes  acaaipaaa oltirkthys !ar|«(entraa -  utei  uiatlil i i i ret Mat  i rat h i c h i hy o i d e • hppUftethai p aratratki c ht byt cvprinodontrTormes apticaeUafcari  • brod l el • ™ " " ,t  Uybliailllrf  F i g u r e 2.4:  annirllldar  ,e l-M  lialil  f 1|aatarkyathai lat it m i c a aaiiiMaalit , 1 didp*y<hr alii pUiybrlnnr argalas lovii i i.ihuhthodt > afflaij aalaiyx u ' u t i t i i l i f l * j a » i a apercalajls haloiratiui i autfimaolatus •alaccMrai alaacMa balatcartrai i n a a u •alaccBiTis mttki haleceatrai rafai halaccairai ipinaii vstiaus halaceatras lartafM aryripriitis aduita -•aiyiiam*il ausuills Hyripriitis | i . o b u . Myripriftil mai«|.in •ytlarlstls raadalii Myilprixtis vial acta Myriprinis wiiiatas acaaiphan aurolinr atti a i m hi hyi plbvaxti -»iaraaccniraa alkie Ma idisairnliaa iainifciaai aaamalept kaptoatran anMmm nidi iraaialai baplaftclbai eloagaim M i itrai kkhthyl iidilli ihinnileimri miii.lrpiUuliii iiiaiadl at aanirlla p a k i r *  R u b b e r sheet n a v i g a t i o n a n d g u a r a n t e e d v i s i b i l i t y i n T r e e J u x t a -  poser [37]. F o c u s a n d c o n t e x t r e g i o n s a r e s m o o t h l y i n t e g r a t e d w h i l e p r e s e r v i n g t h e s y m m e t r y o f t h e tree's t o p o l o g y .  Chapter 2. Related Work  2.3  13  Guaranteed Visibility  B o t h p a n a n d z o o m a n d focus+context, n a v i g a t i o n techniques have been shown t o b e effective for e x p l o r i n g d a t a s e t s o f u p to s e v e r a l h u n d r e d i t e m s .  However,  w i t h larger datasets. b o t h classes of n a v i g a t i o n t e c h n i q u e s often e n c o u n t e r visi b i l i t y issues, w h e r e m a r k e d a r e a s o f interest t o t h e u s e r , s u c h as l a n d m a r k s o r search results, c a n n o t be seen.  In p a n a n d z o o m i n t e r f a c e s , t h i s m a y o c c u r b e -  c a u s e a r e a s o f i n t e r e s t m o v e off-screen d u e to n a v i g a t i o n a c t i o n s . In its e x t r e m e f o r m , t h e m o v i n g o f areas o f i n t e r e s t off-screen c a n r e s u l t i n g in a p h e n o m e n o n r e f e r r e d to as d e s e r t f o g [28]. w h e r e t h e user is f a c e d w i t h a v i e w o f t h e dataset. d e v o i d o f n a v i g a t i o n a l cues. T h e m a r k e d areas m a y a l s o b e c o m e s i m p l y t o o s m a l l t o b e d i s p l a y e d a t t h e set s c a l e a n d r e s o l u t i o n . In f o c u s + c o n t e x t  interfaces, ar-  eas o f interest, m a y b e r e n d e r e d i n v i s i b l e d u e to t h e effects o f d i s t o r t i o n , w h i c h c a n l e a d t h e m to b e c u l l e d o r a g g r e g a t e d w i t h n o n - m a r k e d a r e a s .  A common  s o l u t i o n to v i s i b i l i t y issues is t o a u g m e n t the v i s u a l i z a t i o n w i t h a n o v e r v i e w w i n d o w , w h i c h c a n e n a b l e u s e r s to see m a r k e d a r e a s o u t s i d e t h e d e t a i l v i e w . However, overview windows have a n u m b e r of d r a w b a c k s . T h e y take up screen real estate, m a y not p r o v i d e e n o u g h resolution to ensure that m a r k e d areas in large datasets are visible to users, a n d d i v i d e users  1  a t t e n t i o n [51].  T o a d d r e s s t h i s issue, M u n z n e r et a l . [37] i n t r o d u c e t h e c o n c e p t o f g u a r a n t e e d v i s i b i l i t y , t h e p r o p e r t y t h a t m a r k e d a r e a s o f t h e dataset. a r e g u a r a n t e e d to be visible regardless of d a t a s e t  size o r n a v i g a t i o n a c t i o n s t a k e n b y  users.  M u n z n e r et a l . d i f f e r e n t i a t e b e t w e e n t h r e e cases t o c o n s i d e r w h e n g u a r a n t e e i n g v i s i b i l i t y o f m a r k e d areas:  1. O f f - s c r e e n :  A m a r k e d a r e a m a y m o v e o f f - s c r e e n d u e to user n a v i g a t i o n  actions or restrictions o n available screen real estate.  2. S u b - p i x e l : T h e d i m e n s i o n s o f a m a r k e d a r e a m a y s h r i n k t o less t h a n a pixel.  T h i s s i t u a t i o n is p a r t i c u l a r l y l i k e l y to o c c u r w h e n t h e n u m b e r  o f i t e m s in a d a t a s e t is l a r g e r t h a n t h e n u m b e r o f p i x e l s a v a i l a b l e t o t h e visualization.  Chapter 2. Related Work 3.  14  O c c l u s i o n : A m a r k e d a r e a c a n be o c c l u d e d b y o t h e r p a r t s of the dataset. such  as  labels in a t w o - d i m e n s i o n a l  layout  or other  items  in a  three-  dimensional visualization.  M u n z n e r et a l .  [37] i m p l e m e n t e d  all three t y p e s of g u a r a n t e e d visibility in  c o n j u n c t i o n w i t h r u b b e r s h e e t n a v i g a t i o n in t h e p r e v i o u s l y d i s c u s s e d T r e e J u x t a p o s e r s y s t e m , w h i c h serves as t h e b a s i s for t h e r u b b e r s h e e t n a v i g a t i o n  interfaces  d i s c u s s e d i n t h i s thesis. G u a r a n t e e d v i s i b i l i t y h a s a l s o b e e n i m p l e m e n t e d i n seve r a l p a n a n d z o o m interfaces, i n c l u d i n g C i t y L i g h t s [51] a n d H a l o [6]. i l l u s t r a t e d in F i g u r e s 2.5  a n d 2.6,  respectively.  B a s e d on the J a z z p a n a n d z o o m  inter-  face toolkit, [9], C i t y L i g h t s i n d i c a t e s t h e d i r e c t i o n o f off-screen m a r k e d areas v i a c o m p a c t i n d i c a t o r s i n t e g r a t e d a l o n g v i e w b o r d e r s . H a l o [6] d e v e l o p s t h e c o n c e p t o f C i t y L i g h t s f u r t h e r to p r o v i d e a n i n d i c a t i o n o f b o t h d i r e c t i o n a n d d i s t a n c e  to  off-screen m a r k e d a r e a s in t h e context, o f s m a l l - s c r e e n d e v i c e s . M a r k e d a r e a s a r e s u r r o u n d e d w i t h rings that are just large e n o u g h to reach into the b o r d e r regions o f t h e v i s u a l i z a t i o n . T h e r i n g s e n a b l e u s e r s to d i s c e r n t h e a p p r o x i m a t e  location  of the m a r k s , while using a r e l a t i v e l y s m a l l p r o p o r t i o n of the available  screen  r e a l e s t a t e . In a, c o n t r o l l e d e x p e r i m e n t , H a l o was f o u n d t o i m p r o v e p e r f o r m a n c e o n a n a v i g a t i o n task c o m p a r e d to a n a r r o w - b a s e d technique  that, similarly to  C i t y L i g h t s , o n l y i n d i c a t e d d i r e c t i o n t o off-screen m a r k e d a r e a s . T h i s result m o t i v a t e d o u r use o f H a l o - l i k e a r c s t o p r o v i d e off-screen  guaranteed  visibility in  the p a n a n d z o o m n a v i g a t i o n interfaces e x a m i n e d in o u r studies.  2.4  Evaluation of Navigation Techniques  T o date,  no empirical evaluation  o f r u b b e r sheet n a v i g a t i o n  the information visualization literature. compared other focus+context faces.  appeared  However, a n u m b e r of evaluations  navigation  O n e o f t h e first s u c h e v a l u a t i o n s  has  techniques  was p r e s e n t e d  to p a n a n d z o o m  in  have inter-  b y S c h a f l e r et a l .  [46].  w h o c o m p a r e d a z o o m i n g i n t e r f a c e t o a fisheyc i n t e r f a c e for p e r f o r m i n g a n a v i g a t i o n a n d r o u t i n g task in a h i e r a r c h i c a l l y c l u s t e r e d n e t w o r k d a t a s e t .  Results  Chapter 2. Related Work  F i g u r e 2.6: screen  G u a r a n t e e d v i s i b i l i t y i n H a l o [6].  m a r k e d areas  are indicated by arcs that  rings d r a w n a r o u n d the m a r k e d areas.  IS  Direction a n d distance represent  to  visible portions  offof  Chapter 2. Related Work  16  s h o w e d t h a t t h e fisheye i n t e r f a c e r e s u l t e d in s i g n i f i c a n t l y l o w e r c o m p l e t i o n t i m e s a n d was preferred b y  subjects.  G u t w i n a n d S k o p i k [22] c o m p a r e d fisheye i n t e r f a c e s u s i n g t h r e e different d i s t o r t i o n m o d e l s t o t w o p a n n i n g i n t e r f a c e s w i t h o v e r v i e w s for p e r f o r m i n g a l a r g e steering task.  R e s u l t s i n d i c a t e d t h a t all t h e fisheye  interfaces e n a b l e d  faster  task c o m p l e t i o n t h a n either o f the p a n n i n g interfaces, a l t h o u g h this finding was p a r t i a l l y e x p l a i n e d b y the i m p l e m e n t a t i o n s h o r t c o m i n g s of one of the p a n n i n g interfaces.  G u t w i n f o l l o w e d u p t h i s s t u d y w i t h a n o t h e r i n v e s t i g a t i o n [21], w h i c h  c o m p a r e d fisheye, p a n n i n g , a n d t w o - l e v e l z o o m i n t e r f a c e s for e d i t i n g , w e b n a v igation, a n d m o n i t o r i n g tasks.  T h a t s t u d y f o u n d t h a t the  fisheye  interface  was  s i g n i f i c a n t l y f a s t e r for t h e w e b n a v i g a t i o n . t a s k , b u t t h e z o o m i n t e r f a c e p e r f o r m e d b e t t e r o n t h e m o n i t o r i n g t a s k a n d was  strongly p r e f e r r e d  by subjects.  H o r n b a e k a n d F r o k j a e r [25] c o m p a r e d p a n n i n g i n t e r f a c e s w i t h a n d w i t h o u t , o v e r v i e w s t o a fisheye  i n t e r f a c e for r e a d i n g e l e c t r o n i c d o c u m e n t s .  That  study  f o u n d t h a t s u b j e c t s r e a d d o c u m e n t s faster w h e n u s i n g the fisheye i n t e r f a c e t h a n when  using either of the  p a n n i n g interfaces.  H o w e v e r , the p a n n i n g  interface  w i t h an overview p r o v i d e d better c o m p r e h e n s i o n a n d was preferred by subjects. Baudisch, Lee, and Hanna  [5] p e r f o r m e d a c o m p a r a t i v e s t u d y o f t h r e e  faces s i m i l a r t o t h o s e e x a m i n e d b y H o r n b a e k a n d F r o k j a e r .  B o t h the  interfisheye  interface a n d the p a n n i n g interface with an overview p r o v i d e d g u a r a n t e e d visibility of m a r k e d areas, while  the p a n n i n g interface w i t h o u t  an overview did  n o t . A l t h o u g h r e s u l t s for b o t h p e r f o r m a n c e a n d s u b j e c t p r e f e r e n c e w e r e h i g h l y d e p e n d e n t o n t h e t a s k , t h e t w o interfaces w i t h g u a r a n t e e d v i s i b i l i t y were faster t h a n t h e c o m p a r i s o n i n t e r f a c e for m o s t t a s k s a n d w e r e p r e f e r r e d b y a l l s u b j e c t s , a  finding  t h a t m o t i v a t e d o u r use o f g u a r a n t e e d v i s i b i l i t y i n t h e i n t e r f a c e s  a m i n e d in o u r e x p e r i m e n t . investigate  B a u d i s c h et a l .  the p o t e n t i a l benefits  ex-  also suggested that future studies  of c o m b i n i n g focus+context. n a v i g a t i o n  with  o v e r v i e w s , w h i c h c o r r e s p o n d s t o o n e o f the i n t e r f a c e s e x a m i n e d in o u r e x p e r i ment. T h e evaluation presented  in t h i s thesis a t t e m p t s  l i m i t a t i o n s o f s c o p e s h a r e d b y these s t u d i e s .  First,  to o v e r c o m e a n u m b e r of the n o n - d i s t o r t i o n inter-  Chapter 2. Related Work faces u s e d i n t h e s e s t u d i e s  17  p r o v i d e d either p a n n i n g or z o o m i n g capabilities,  b u t not b o t h . P a n n i n g a n d z o o m i n g are i n c r e a s i n g l y used together in b o t h research a n d c o m m e r c i a l interfaces, a n d some evaluations of interfaces c o m b i n i n g these t w o t e c h n i q u e s h a v e a p p e a r e d i n t h e l i t e r a t u r e , m o s t n o t a b l y H o r n b a e k et a l . s c o m p a r i s o n o f p a n a n d z o o m i n t e r f a c e s w i t h a n d w i t h o u t o v e r v i e w s [24]. ;  H o w e v e r , c o m b i n e d p a n a n d z o o m i n t e r f a c e s h a v e not to d a t e b e e n e m p i r i c a l l y c o m p a r e d to focus+context  interfaces. S e c o n d , all the a b o v e - m e n t i o n e d studies  u s e d v a r i a t i o n s o n the fisheye i n t e r f a c e p a r a d i g m .  T h e w o r k presented in this  thesis seeks t o e x p a n d t h e l i t e r a t u r e o n e v a l u a t i o n o f f o c u s + c o n t e x t  interfaces  to i n c l u d e r u b b e r sheet n a v i g a t i o n , w h i c h r e p r e s e n t s o n e p o t e n t i a l a l t e r n a t i v e t o fisheye  views.  Third,  a l t h o u g h t h e fisheye  interfaces used  in G u t w i n  and  S k o p i k s s t u d y [22] p r o v i d e d c o n t e x t i n different w a y s d e p e n d i n g o n t h e i r d i s ;  t o r t i o n m o d e l s , neither this s t u d y n o r any of the others discussed in this section e x a m i n e d l e v e l o f c o n t e x t as a f a c t o r . F o u r t h , n o n e o f t h e s t u d i e s  investigated  augmenting focus+context  i n t e r f a c e s w i t h o v e r v i e w s to d e t e r m i n e w h e t h e r t h i s  would compensate  d r a w b a c k s of distortion, a l i m i t a t i o n discussed  for t h e  m o r e d e t a i l i n B o d n a r s t h e s i s [12]. b y S c h a f f e r et a l .  in  F i n a l l y , a p a r t from the s t u d y p e r f o r m e d  [46], t h e e v a l u a t i o n s d i s c u s s e d a b o v e d i d not  rely on  tasks  o r d a t a s e t s d e r i v e d f r o m r e a l - w o r l d a p p l i c a t i o n s , a l i m i t a t i o n a d d r e s s e d in o u r s t u d y t h r o u g h the choice o f a n ecologically valid task a n d dataset inspired b y the needs of phylogenetic biologists.  2.5  Evaluation of Tree Visualizations  T h e w o r k d e s c r i b e d in t h i s t h e s i s is r e l a t e d to a n o t h e r b r a n c h o f t h e l i t e r a t u r e o n e v a l u a t i o n o f i n f o r m a t i o n v i s u a l i z a t i o n s , n a m e l y user s t u d i e s o f tree v i s u a l ization techniques.  In p a r t i c u l a r , t w o r e c e n t s t u d i e s h a v e p e r f o r m e d c o n t r o l l e d  e x p e r i m e n t s i n v o l v i n g i n t e r f a c e s for v i s u a l i z i n g l a r g e tree d a t a s e t s . Kobsa  [30] c o m p a r e d five t r e e v i s u a l i z a t i o n i n t e r f a c e s , as w e l l as W i n d o w s  E x p l o r e r , w h i c h was u s e d as a b a s e l i n e for c o m p a r i s o n . K o b s a s s t u d y u s e d a :  h i e r a r c h i c a l t r e e d a t a s e t o f m o r e t h a n 5,700 n o d e s a m i a v a r i e t y o f t a s k s r e l a t e d  Chapter 2. Related Work  18  to b o t h d a t a s e t t o p o l o g y a n d i t e m a t t r i b u t e s . W i n d o w s E x p l o r e r o u t p e r f o r m e d the c o m p a r i s o n interfaces a n d was also p r e f e r r e d b y most s u b j e c t s , the difficulty o f c o m p a r i n g a n interface  highlighting  w i t l i w h i c h users h a v e e x p e r i e n c e  t h o s e t h e y a r e e n c o u n t e r i n g for t h e first t i m e .  T h e c o m p a r i s o n was  confounded  by t h e f a c t t h a t s o m e i n t e r f a c e s w e r e m i s s i n g f u n c t i o n a l i t y r e q u i r e d t o some of the  to  complete  tasks.  P l a i s a n t . G r o s j e a n . a n d B e d e r s o n [43] c o m p a r e d t h e i r S p a c e T r e e t o o l , w h i c h used a n o n - d i s t o r t i o n - b a s e d f o c u s + c o n t e x t i n t e r f a c e , to W i n d o w s E x p l o r e r a n d a h y p e r b o l i c tree browser based on that developed by L a m p i n g . R a o . a n d P i r o l l i [31].  T h e e x p e r i m e n t u s e d a l a r g e tree d a t a s e t o f m o r e t h a n 7 , 0 0 0 n o d e s a n d a  v a r i e t y o f s e a r c h a n d t o p o l o g i c a l t a s k s . T h e r e s u l t s o f t h e s t u d y w e r e m i x e d , rev e a l i n g t h a t S p a c e T r e e p e r f o r m e d s i g n i f i c a n t l y faster for s o m e t o p o l o g i c a l t a s k s , b u t n o t for o t h e r s , w i t h n o s i g n i f i c a n t d i f f e r e n c e s i n t e r m s o f s u b j e c t A c o m m o n l i m i t a t i o n t o b o t h t h e s e s t u d i e s is t h a t t h e i n t e r f a c e s  preference. examined  used w i d e l y different m e t h o d s of d a t a p r e s e n t a t i o n a n d i n t e r a c t i o n , m a k i n g t h e i r results difficult to interpret.  T h e experiments  described in this thesis a i m  o v e r c o m e t h i s issue b y c o m p a r i n g i n t e r f a c e s t h a t s h a r e v i s u a l p r e s e n t a t i o n i n t e r a c t i o n m e t a p h o r s a n d differ o n l y i n t e r m s o f n a v i g a t i o n  technique.  to  and  19  Chapter 3  Task and Dataset I n o r d e r t o l e n d e c o l o g i c a l v a l i d i t y to o u r e x p e r i m e n t , we d e r i v e d t h e t a s k a n d dataset  u s e d i n it f r o m t h e d o m a i n o f p h y l o g e n e t i c b i o l o g y .  Phylogenetic bi-  ologists  m o d e l e v o l u t i o n a r y r e l a t i o n s h i p s as h i e r a r c h i c a l t r e e s i n a n effort  i m p r o v e their u n d e r s t a n d i n g of how different organisms evolve a n d  to  co-evolve.  T h e recent flood of m o l e c u l a r data o b t a i n e d from D N A a n d protein sequencing h a s e n a b l e d t h e c o n s t r u c t i o n o f p h y l o g e n e t i c t r e e s o f e v e r - i n c r e a s i n g size.  To-  d a y , s o m e g r o u p s o f p h y l o g e n e t i c b i o l o g i s t s h a v e c o n s t r u c t e d trees c o n t a i n i n g thousands of nodes,  a n d m a n y hope soon to be able to r e c o n s t r u c t the  p l e t e T r e e o f L i f e , e s t i m a t e d t o c o n t a i n o v e r t e n m i l l i o n s p e c i e s [37].  com-  However,  a r e c e n t s u r v e y [15] p o i n t s o u t t h a t p r o g r e s s h a s b e e n h a m p e r e d b y a l a c k o f tools s u p p o r t i n g e x p l o r a t i o n , visual inspection, a n d s t r u c t u r a l c o m p a r i s o n in such large datasets.  T h i s c h a p t e r d o c u m e n t s the choice of o u r task a n d dataset  based on the r e q u i r e m e n t s of this d o m a i n .  3.1  Task  T o gain an u n d e r s t a n d i n g of the tasks i n v o l v e d in phylogenetic analysis of large tree d a t a s e t s u s i n g i n f o r m a t i o n v i s u a l i z a t i o n t o o l s , we c o n d u c t e d i n t e r v i e w s w i t h ten p h y l o g e n e t i c biologists from universities in C a n a d a a n d the U n i t e d States. W e l e a r n e d t h a t p h y l o g e n e t i c b i o l o g i s t s use  interactive v i s u a l i z a t i o n s of large  e v o l u t i o n a r y trees to g a i n a d e e p e r u n d e r s t a n d i n g o f the r e l a t i o n s h i p s a n d w i t h i n g r o u p s of o r g a n i s m s .  between  T h r o u g h the process of topological analysis,  these r e s e a r c h e r s a i m t o d e t e r m i n e how- s p e c i e s h a v e e v o l v e d a n d c o - e v o l v e d , a n d h o w c h a r a c t e r i s t i c s a r e p a s s e d f r o m o n e s p e c i e s t o the n e x t i n a n e v o l u t i o n a r y  Chapter 3. Task and Dataset  20  lineage. B a s e d o n o u r d i s c u s s i o n s , we d e v e l o p e d a set o f f o u r t a s k s , d e s c r i b e d a n d i l l u s t r a t e d b e l o w , w h i c h were r e p r e s e n t a t i v e o f t h e t r e e - t o p o l o g i c a l t a s k s p e r formed b y phylogenetic biologists, b u t d i d not require specialized knowledge of e v o l u t i o n a r y trees. W e t h e n v a l i d a t e d these t a s k s w i t h s e v e r a l o f t h e b i o l o g i s t s we h a d p r e v i o u s l y i n t e r v i e w e d t o e n s u r e t h e t a s k s ' e c o l o g i c a l v a l i d i t y . E a c h of the identify, and  tasks  was  c o m p o s e d o f s e v e r a l l o w - l e v e l t a s k s s u c h as  find,  a n d c o m p a r e , as d e s c r i b e d i n t h e v i s u a l t a s k t a x o n o m y o f W e h r e n d  L e w i s [49].  I n the illustrations below, a c o l o r e d n o d e represents a species,  w h e r e a s a c o l o r e d s u b t r e e r e p r e s e n t s a r e l a t e d g r o u p o f species.  3.1.1  T a s k 1: D e t e r m i n i n g t h e l o w e s t c o m m o n a n c e s t o r  In a p h y l o g e n e t i c tree, t h e l o w e s t c o m m o n a n c e s t o r o f t w o n o d e s is a n o r g a n i s m t h a t is a n a n c e s t o r o f b o t h t h e s p e c i e s i n q u e s t i o n , a n d t h a t h a s g r e a t e s t d e p t h i n t h e tree, as i l l u s t r a t e d i n F i g u r e 3.1.  the  D e t e r m i n i n g t h e lowest  c o m m o n a n c e s t o r is a n i m p o r t a n t t a s k i n p h y l o g e n e t i c t a x o n o m y , a b r a n c h of p h y l o g e n e t i c b i o l o g y c o n c e r n e d w i t h c l a s s i f y i n g s p e c i e s b a s e d o n p h y l o g e n e t i c data.  1  F i g u r e 3.1:  Task  1:  r-M  D e t e r m i n i n g t h e lowest c o m m o n a n c e s t o r .  n o d e A is t h e lowest c o m m o n a n c e s t o r of n o d e s B a n d C .  I n t h i s case,  Chapter 3. Task and  3.1.2  21  Dataset  Task 2: Comparing the topological distances between nodes  T o p o l o g i c a l d i s t a n c e i n a tree is t h e n u m b e r o f h o p s b e t w e e n t w o n o d e s , a n d is n o t t h e s a m e as g e o m e t r i c d i s t a n c e , w h i c h m a y c h a n g e w i t h n a v i g a t i o n , as i l l u s t r a t e d i n F i g u r e 3.2.  I n a p h y l o g e n e t i c tree, t h e t o p o l o g i c a l d i s t a n c e b e -  t w e e n two n o d e s is i n d i c a t i v e o f t h e n u m b e r o f e v o l u t i o n a r y s t e p s b e t w e e n species t h e y represent.  the  M e a s u r i n g a n d c o m p a r i n g t o p o l o g i c a l d i s t a n c e s is o n e  o f t h e p r i m a r y t a s k s for w h i c h p h y l o g e n e t i c b i o l o g i s t s r e q u i r e v i s u a l i z a t i o n s o f e v o l u t i o n a r y trees.  F i g u r e 3.2: T a s k 2: C o m p a r i n g t h e t o p o l o g i c a l d i s t a n c e s b e t w e e n n o d e s . I n t h i s case, n o d e A is 2 t o p o l o g i c a l h o p s f r o m n o d e B a n d 3 t o p o l o g i c a l h o p s  from  n o d e C , m a k i n g n o d e B t o p o l o g i c a l l y closer.  3.1.3  Task 3: Determining whether two subtrees are adjacent  I n a t r e e , t w o s u b t r e e s a r e a d j a c e n t if n o o t h e r n o d e is b e t w e e n t h e m , as i l l u s t r a t e d i n F i g u r e 3.3.  In phylogenetic biology, this task represents d e t e r m i n i n g  w h e t h e r t h e g r o u p s of s p e c i e s r e p r e s e n t e d b y t h e s u b t r e e s are s i s t e r  groups,  or g r o u p s o f o r g a n i s m s w h o a r e m o s t c l o s e l y r e l a t e d t o o n e a n o t h e r i n t e r m s o f t h e i r e v o l u t i o n a r y h i s t o r y (for i n s t a n c e , great a p e s a n d m o n k e y s ) .  Chapter  F i g u r e 3.3:  T a s k 3:  3. Task and Dataset  22  D e t e r m i n i n g w h e t h e r two s u b t r e e s a r e a d j a c e n t .  In this  case, t h e s u b t r e e s l a b e l e d A a n d B are not a d j a c e n t .  3.1.4  T a s k 4: D e t e r m i n i n g w h e t h e r a s u b t r e e c o n t a i n s u n m a r k e d nodes  In a p h y l o g e n e t i c tree, m a r k e d n o d e s m a y i n d i c a t e t h e p r e s e n c e o f a u n i q u e feature or  character.  T h e presence of uncolored nodes or subtrees in a m a r k e d  s u b t r e e , s h o w n i n F i g u r e 3.4, m a y t h e r e f o r e i n d i c a t e a  character reversal,  an  event c a u s i n g t h e loss o f a c h a r a c t e r f o r m e r l y p r e s e n t i n a n e v o l u t i o n a r y l i n e (for e x a m p l e , t h e loss o f a t a i l i n g r e a t a p e s a n d h u m a n s ) .  11  A i  i 1•  1t  i — * Z  T  F i g u r e 3.4:  T a s k 4: D e t e r m i n i n g w h e t h e r a s u b t r e e c o n t a i n s u n m a r k e d n o d e s .  In t h i s case, t h e s u b t r e e l a b e l e d A c o n t a i n s a n u n m a r k e d n o d e , B .  Chapter  3.  Task and Dataset  23  A f t e r t h e d e v e l o p m e n t o f t h e set o f t a s k s d e s c r i b e d a b o v e , we d e c i d e d  to  f o c u s o u r s t u d y o n a s i n g l e t a s k in o r d e r t o l i m i t t h e effect o f t a s k as a f a c t o r . T a s k 2 w a s selected for f u r t h e r i n v e s t i g a t i o n d u e to its r e l a t i v e c o m p l e x i t y , h i g h i m p o r t a n c e to p h y l o g e n e t i c a n a l y s i s , a n d t h e fact t h a t it w o u l d r e q u i r e s u b j e c t s to p e r f o r m m u l t i p l e n a v i g a t i o n actions a l o n g well-defined p a t h s , thus r e d u c i n g performance variability. T a s k i n s t a n c e s w e r e a s s e s s e d in p i l o t s t u d i e s  to e n s u r e t h a t t h e y w e r e iso-  m o r p h i c i n difficulty. I n p a r t i c u l a r , t o p o l o g i c a l d i s t a n c e s b e t w e e n n o d e s  always  fell i n a r a n g e o f 7 t o 10, a n d c o u l d n o t b e d e t e r m i n e d w i t h o u t i n t e r a c t i n g w i t h t h e i n t e r f a c e for a n y o f t h e t a s k i n s t a n c e s .  A l s o , colored nodes were not l o c a t e d  in c l o s e p r o x i m i t y t o e a c h o t h e r in o r d e r to e n s u r e t h a t a t l e a s t o n e i n t e r a c t i o n had  to b e p e r f o r m e d to d e t e r m i n e e a c h t o p o l o g i c a l d i s t a n c e .  3.2 The  Dataset dataset  u s e d for i n i t i a l p i l o t i n g for o u r s t u d y was t h e  animaliaA  dataset  f r o m t h e 2 0 0 3 Infovis C o n t e s t [42]. a p h y l o g e n e t i c tree o f a p p r o x i m a t e l y 1 9 0 , 0 0 0 n o d e s r e p r e s e n t i n g a h y p o t h e s i s a b o u t t h e e v o l u t i o n o f o r g a n i s m s in the k i n g d o m Animalia.  I n i t i a l p i l o t r e s u l t s s u g g e s t e d t h a t t h i s dataset. w a s n o t a n o p t i m a l  c h o i c e for o u r e x p e r i m e n t . Its t o p o l o g y w a s n o t s u f f i c i e n t l y d e e p t o r e q u i r e s u b j e c t s t o p e r f o r m a l a r g e a m o u n t , o f n a v i g a t i o n , w h i l e its s i z e n e c e s s i t a t e d t i m e s o f u p to 45 s e c o n d s  for o u r v i s u a l i z a t i o n t o o l s .  F o r this reason,  start subse-  quent, p i l o t i n g a n d t h e f o r m a l e x p e r i m e n t u s e d t h e  phylogenyMatchesTaxonomy  dataset,  w h i c h also represents e v o l u -  a b i n a r y tree c o n s i s t i n g o f 5,918  nodes,  t i o n a r y r e l a t i o n s h i p s b e t w e e n s p e c i e s t h e k i n g d o m Animalia.  T h i s dataset.  was  u s e d c o u r t e s y o f D a v i d H i ] 1 is o f t h e U n i v e r s i t y o f T e x a s , a n d is a v a i l a b l e f r o m t h e O l d u v a i project, w e b s i t e [39].  T h i s dataset  a l l o w e d for c o m p l e x  topologi-  cal c o m p a r i s o n s r e q u i r i n g a s i g n i f i c a n t a m o u n t o f n a v i g a t i o n w h i l e r e d u c i n g t h e start t i m e s for o u r t o o l s t o u n d e r 5 s e c o n d s . Although  we h a d o r i g i n a l l y a s s u m e d  that, n o d e  l a b e l s were i m p o r t a n t  to  t h e w a y b i o l o g i s t s i n t e r a c t w i t h p h y l o g e n e t i c tree v i s u a l i z a t i o n s , o u r d i s c u s s i o n s  Chapter  3. Task and Dataset  24  w i t h b i o l o g i s t s revealed t h a t t h e i r t y p i c a l use o f e v o l u t i o n a r y trees i n v o l v e d v e r y l i t t l e l a b e l r e a d i n g . W e t h e r e f o r e r e m o v e d n o d e l a b e l s f r o m t h e d a t a s e t for t h e purpose of o u r studies.  U s i n g n o l a b e l s e n a b l e d us t o a v o i d u n n e c e s s a r y  node  occlusion a n d potential c o n f o u n d i n g of experimental results b y subjects'  prior  k n o w l e d g e of e v o l u t i o n a r y r e l a t i o n s h i p s between species.  25  Chapter 4  Study 1 T h e goal of S t u d y  1 was  to e x a m i n e  t h e effect o f level o f c o n t e x t o n p e r f o r -  m a n c e in interfaces w i t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n . T h e s t u d y i n v o l v e d four different interfaces, r e p r e s e n t i n g all c o m b i n a t i o n s of the two n a v igation techniques  with and without  an overview,  as i l l u s t r a t e d i n T a b l e  4.1.  S u b j e c t s u s e d t h e s e i n t e r f a c e s w i t h v a r y i n g levels o f c o n t e x t t o s o l v e a t o p o l o g ical task in a large tree dataset.  T h e level of context t h a t resulted in the  p e r f o r m a n c e for e a c h i n t e r f a c e w a s t h e n the four interfaces the study,  used to c o m p a r e the p e r f o r m a n c e of  i n S t u d y 2. d e s c r i b e d i n C h a p t e r 5.  presents the results related  best  T h i s chapter  t o t h e effects o f n a v i g a t i o n  describes technique,  a n d d i s c u s s e s t h e i r i m p l i c a t i o n s a n d t h e w a y t h e y affected S t u d y 2. T h e r e s u l t s r e l a t e d t o t h e effects o f p r e s e n c e o r a b s e n c e o f o v e r v i e w a n d t h e i r i m p l i c a t i o n s a r e d i s c u s s e d i n d e t a i l i n B o d n a r s t h e s i s [12].  ^  N  a  v  i  g  a  t  i  o  n Rubber  Overview Not  present  Present T a b l e 4.1:  Pan  and  Zoom  RSN-NoOV  PZN-NoOV  RSN+OV  PZN+OV  Interfaces r e p r e s e n t i n g all c o m b i n a t i o n s of the n a v i g a t i o n a n d pres-  ence of overview S t u d y 2.  Sheet  —  factors.  A l l four i n t e r f a c e s  were u s e d  in b o t h S t u d y  1 and  Chapter 4. Study 1  4.1  26  Hypotheses  O u r p r i m a r y h y p o t h e s i s for t i n s s t u d y w a s t h a t p e r f o r m a n c e i n e a c h  interface  w o u l d vary w i t h the level of context a c c o r d i n g to a U - s h a p e d curve, w i t h v e r y l o w a n d v e r y h i g h c o n t e x t levels r e s u l t i n g i n p o o r p e r f o r m a n c e c o m p a r e d t o v a l ues b e t w e e n t h e s e t w o e x t r e m e s .  W e e x p e c t e d t h a t l o w levels o f c o n t e x t  would  n o t p r o v i d e sufficient r e s o l u t i o n t o e n a b l e u s e r s to o b t a i n c o n t e x t u a l c u e s , w h i l e h i g h levels o f c o n t e x t w o u l d c o n s t r a i n t h e a m o u n t o f s c r e e n r e a l e s t a t e a v a i l a b l e t o s h o w features o f i n t e r e s t t o u s e r s a n d t h e r e f o r e a d v e r s e l y i m p a c t n a v i g a t i o n . S i m i l a r l y , we e x p e c t e d  t h a t , i n i n t e r f a c e s w i t h o v e r v i e w s , s m a l l o v e r v i e w sizes  w o u l d p r o v i d e i n s u f f i c i e n t r e s o l u t i o n , w h i l e l a r g e o v e r v i e w sizes w o u l d d e t r a c t f r o m the n a v i g a t i o n w i t h i n the d e t a i l views. sented  HI:  T h e resulting hypotheses are pre-  below.  F o r b o t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n , m e d i u m levels of context w i t h i n the detail v i e w will perforin b e t t e r t h a n either h i g h o r low levels o f c o n t e x t .  H2:  In i n t e r f a c e s w i t h o v e r v i e w s , m e d i u m s i z e d o v e r v i e w s w i l l p e r f o r m  better  than either s m a l l or large overviews.  T h e v a l u e s for s m a l l , m e d i u m , a n d l a r g e levels o f c o n t e x t a n d o v e r v i e w sizes for e a c h i n t e r f a c e w e r e c h o s e n b a s e d o n r e s u l t s o f p i l o t s t u d i e s , a n d a r e l i s t e d i n S e c t i o n 4.6.  D u e to t h e v a r i a t i o n o f l e v e l s o f c o n t e x t a n d o v e r v i e w s i z e s w i t h i n  i n t e r f a c e s in t h i s s t u d y , n o specific h y p o t h e s e s w e r e d e v e l o p e d for t h e effects o f n a v i g a t i o n technique o r presence of overview on p e r f o r m a n c e , factors t h a t were i n v e s t i g a t e d in m o r e d e t a i l in S t u d y 2.  4.2  Interfaces  T h e i n t e r f a c e s e x a m i n e d i n t h i s s t u d y a r e i l l u s t r a t e d i n F i g u r e s 4.1 t o 4.4. o r d e r to p r o v i d e c o n s i s t e n t  visual representation,  In  drawing performance, and  Chapter 4. Study 1  27  F i g u r e 4.2: P Z N - N o O V i n t e r f a c e u s e d i n S t u d y 1. A z o o m a c t i o n h a s filled t h e e x t e n t o f t h e t o p v i e w . A r c s i n s p i r e d b y H a l o [6] i n d i c a t e d i r e c t i o n a n d d i s t a n c e t o off-screen m a r k e d n o d e s .  Chapter 4. Study 1  F i g u r e 4.3:  R S N + O V i n t e r f a c e u s e d i n S t u d y 1.  the region shown b y the  field-of-view  28  A z o o m action has stretched  b o x i n t h e o v e r v i e w t o fill t h e t o p  focus  region of the detail view.  F i g u r e 4.4:  P Z N + O V i n t e r f a c e u s e d i n S t u d y 1.  A z o o m a c t i o n h a s filled t h e  e x t e n t o f t h e t o p d e t a i l v i e w w i t h t h e r e g i o n s h o w n b y t h e field-of-view b o x i n the overview.  Chapter 4. Study 1  29  i n t e r a c t i o n m o d e l , all interfaces were b u i l t on the P R I S A D software t u r e [47], [37].  based o n the T r e e J u x t a p o s e r scalable  T h e use o f t h e P R 1 S A D  t i o n t i m e for t h e i n t e r f a c e s . Focus+Context  tree v i s u a l i z a t i o n  i n f r a s t r u c t u r e also h e l p e d  reduce  infrastrucapplication  implementa-  W h i l e T r e e J u x t a p o s e r w a s i n i t i a l l y d e v e l o p e d as a  visualization tool u s i n g r u b b e r sheet n a v i g a t i o n , the  inherent  s i m i l a r i t i e s b e t w e e n r u b b e r s h e e t a n d p a n a n d z o o m n a v i g a t i o n a l l o w e d us  to  e x t e n d its b e h a v i o u r t o s u p p o r t c o n v e n t i o n a l p a n a n d z o o m i n t e r a c t i o n , as w e l l v a r y i n g levels o f c o n t e x t , o v e r v i e w s , the i m p l e m e n t a t i o n  a n d m u l t i p l e foci.  T h i s section discusses  of each of these interface c o m p o n e n t s  and then  examines  the interfaces themselves in d e t a i l .  4.2.1  Navigation  T h e o r i g i n a l T r e e J u x t a p o s e r a p p l i c a t i o n [37] used r u b b e r s h e e t - s t y l e e x p a n s i o n s a n d c o n t r a c t i o n s o f a r b i t r a r y r e c t i l i n e a r r e g i o n s for n a v i g a t i o n , a n d i n c l u d e d a d v a n c e d f e a t u r e s s u c h as l i n k e d n a v i g a t i o n b e t w e e n m u l t i p l e trees. N a v i g a t i o n i n T r e e J u x t a p o s e r e n a b l e d users to select r e c t a n g u l a r regions u s i n g m o u s e drags, a n d resize t h e i r s e l e c t i o n b o x to a r b i t r a r y size. W e r e p l a c e d t h i s s t y l e o f n a v i g a t i o n w i t h a u n i f i e d set o f n a v i g a t i o n a c t i o n s i m p l e m e n t e d  across all  interfaces.  A l l i n t e r a c t i o n o c c u r r e d t h o u g h m o u s e drags, a n d in o u r s u b s e q u e n t a d i s c r e t e n a v i g a t i o n a c t i o n refers t o a s i n g l e m o u s e d r a g . smoothly faces.  analysis,  A l l t r a n s i t i o n s were  a n i m a t e d a c r o s s 20 f r a m e s t o e n s u r e f l u i d i n t e r a c t i o n w i t h t h e i n t e r -  In e a c h i n t e r f a c e ,  with a scroll wheel,  n a v i g a t i o n was controlled u s i n g a two b u t t o n  with zoom  in m a p p e d  to t h e  left m o u s e b u t t o n ,  mouse  panning  m a p p e d t o t h e r i g h t m o u s e b u t t o n , a n d z o o m o u t m a p p e d to t h e s c r o l l w h e e l . Each  interface  also supported  a reset function,  which was  mapped  t o the  R  key. S i m i l a r t o r u b b e r sheet n a v i g a t i o n as i m p l e m e n t e d i n T r e e J u x t a p o s e r , o u r i m p l e m e n t a t i o n o f r u b b e r sheet n a v i g a t i o n a l l o w e d u s e r s t o s e l e c t a r e c t a n g u l a r r r e g i o n u s i n g m o u s e d r a g s . H o w e v e r , i n o u r i m p l e m e n t a t i o n , s e l e c t i o n b o x e s were a l w a y s e x p a n d e d i n t o focus a r e a s o f fixed size a n d a s p e c t r a t i o . T h e  dimensions  o f t h e focus a r e a s w e r e fixed in o r d e r t o e n s u r e t h a t t h e level o f c o n t e x t r e m a i n e d  Chapter 4. Study 1  30  c o n s t a n t r e g a r d l e s s o f user i n t e r a c t i o n s .  4.2.2  Overviews and Foci  O v e r v i e w s w i t h m o v a b l e field o f v i e w b o x e s w e r e p r e s e n t in two o f t h e i n t e r f a c e s . F o r c o n s i s t e n c y b e t w e e n i n t e r f a c e s ; t h e v i e w d i m e n s i o n s in e a c h i n t e r f a c e w e r e c h o s e n to e q u a l i z e t h e t o t a l s c r e e n r e a l e s t a t e a c r o s s t h e m , w i t h e a c h i n t e r f a c e always p r o v i d i n g a total of 600,000 pixels of i n f o r m a t i o n .  B a s e d on the guide-  lines d e v e l o p e d b y A h l b e r g a n d S h n e i d e r m a n [2], we e n s u r e d t h a t a l l n a v i g a t i o n a c t i o n s were t i g h t l y c o u p l e d b e t w e e n t h e o v e r v i e w a n d d e t a i l v i e w . F o r t h i s s t u d y , t w o foci w e r e i m p l e m e n t e d i n b o t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n i n t e r f a c e s to a l l o w users t o s i m u l t a n e o u s l y v i e w a n d i n t e r a c t w i t h m u l t i p l e n o n - a d j a c e n t regions of the dataset.  In t h e r u b b e r s h e e t  navi-  g a t i o n i n t e r f a c e s , users c o u l d select o n e o f t w o f o c u s r e g i o n s as t h e t a r g e t for rectilinear z o o m i n g actions, a l l o w i n g t h e m to e x p l o r e two n o n - a d j a c e n t regions of  the d a t a s e t  a t d i f f e r e n t levels o f c o m p r e s s i o n .  In the p a n a n d z o o m inter-  faces, users c o u l d n a v i g a t e i n t w o s e p a r a t e v i e w s , a l l o w i n g t h e m t o e x p l o r e t w o different r e g i o n s o f t h e d a t a s e t  at different scales.  T h e decision to i m p l e m e n t  m u l t i p l e foci w a s m o t i v a t e d b y the s c e n a r i o w h e r e s u b j e c t s w o u l d b e r e q u i r e d t o n a v i g a t e to f e a t u r e s l o c a t e d b e t w e e n t h e t w o foci i n the p r o c e s s o f c o m p l e t i n g our  task.  F o r t h e s e i n s t a n c e s , we e x p e c t e d  r u b b e r sheet n a v i g a t i o n t o  benefit  from the c o n t e x t region between the two foci, w h i c h w o u l d be either not visible or o n l y v i s i b l e i n t h e o v e r v i e w in i n t e r f a c e s u s i n g p a n a n d z o o m n a v i g a t i o n , a s i l l u s t r a t e d i n F i g u r e 4.5.  4.2.3  Guaranteed Visibility a n d Levels of Context  G u a r a n t e e d v i s i b i l i t y o f m a r k e d a r e a s w a s p r o v i d e d in b o t h d e t a i l v i e w s a n d o v e r v i e w s for b o t h p a n a n d z o o m a n d r u b b e r sheet, n a v i g a t i o n i n t e r f a c e s , a n d a d d r e s s e d t h e t h r e e t y p e s o f g u a r a n t e e d v i s i b i l i t y d i s c u s s e d in Sect i o n 2.3.  In  p a r t i c u l a r , s u b - p i x e l g u a r a n t e e d v i s i b i l i t y in a l l i n t e r f a c e s was p r o v i d e d b y the u n d e r l y i n g P R I S A D v i s u a l i z a t i o n f r a m e w o r k [47]. w h i c h e n s u r e d t h a t i t e m s o f  Chapter 4. Study 1  31  A  if  F i g u r e 4.5:  ~  T  M o t i v a t i n g s c e n a r i o for use o f t w o f o c u s areas i n S t u d y 1.  Marked  n o d e A , l o c a t e d b e t w e e n t h e t w o focus a r e a s i n e a c h i n t e r f a c e , is v i s i b l e i n b o t h views i n the R S N + O V interface (above), b u t o n l y i n the overview the P Z N + O V interface(below).  R u b b e r sheet n a v i g a t i o n was t h e r e f o r e e x p e c t e d t o p e r f o r m  better t h a n p a n a n d z o o m n a v i g a t i o n i n this scenario.  Chapter 4. Study 1  32  interest, i n a l l v i e w s w e r e v i s i b l y m a r k e d e v e n w h e n t h e y w e r e c o m p r e s s e d s u b - p i x e l size.  O c c l u s i o n of m a r k e d areas b y other p a r t s o f the dataset  to was  a v o i d e d by using a 2 D r a t h e r t h a n a 3 D s p a t i a l l a y o u t a n d r e m o v i n g labels f r o m our  dataset. Off-screen  terfaces  guaranteed  v i s i b i l i t y was  implemented  in the  experimental  i n different w a y s d e p e n d i n g o n n a v i g a t i o n t e c h n i q u e .  in-  In r u b b e r s h e e t  i n t e r f a c e s ; n a v i g a t i o n w a s c o n s t r a i n e d so t h a t i t e m s o u t s i d e t h e f o c u s a r e a s w e r e c o m p r e s s e d in context areas a l o n g the p e r i p h e r y of the view.  In p a n a n d z o o m  i n t e r f a c e s , d i r e c t i o n t o a n d d i s t a n c e f r o m off-screen m a r k e d a r e a s were e n c o d e d u s i n g o p a q u e elliptical arcs s i m i l a r to those i m p l e m e n t e d in B a u d i s c h a n d R o s e n h o l t z s H a l o [6]. :  A s i n r u b b e r sheet n a v i g a t i o n i n t e r f a c e s , t h e s e a r c s a p p e a r e d  in p e r i p h e r a l c o n t e x t a r e a s a l o n g t h e e d g e s o f a v i e w .  H o w e v e r , these  context  areas were not explicitly v i s u a l l y delimited, their resolution d i d not change, a n d t h e i r s h a p e w a s oval r a t h e r t h a n r e c t a n g u l a r . A l t h o u g h t h e d e g r e e o f c o n t e x t u a l i n f o r m a t i o n p r o v i d e d by c o n t e x t areas in b o t h n a v i g a t i o n techniques varied w i t h u s e r i n t e r a c t i o n , we u s e d t h e t o t a l e x t e n t o f t h e s e a r e a s as a n a p p r o x i m a t i o n for the a m o u n t of context w i t h i n each interface. In  a d d i t i o n to p e r i p h e r a l c o n t e x t  areas,  contextual  i n f o r m a t i o n was  also  p r o v i d e d b y overviews in those interfaces t h a t c o n t a i n e d t h e m . F o r the p u r p o s e o f v a r y i n g t h e level o f c o n t e x t i n t h i s s t u d y , we t h e r e f o r e d i s t i n g u i s h e d b e t w e e n two p o s s i b l e  levels o f c o n t e x t  i n e a c h i n t e r f a c e , i l l u s t r a t e d i n F i g u r e s 4.6  and  4.7:  1. L e v e l o f n a v i g a t i o n a l c o n t e x t : F r a c t i o n o f size o f n a v i g a t i o n - s p e c i f i c context view  areas C to t h e t o t a l size o f f o c u s a n d c o n t e x t  areas in the d e t a i l  F+C.  2. L e v e l o f o v e r v i e w c o n t e x t : F r a c t i o n o f size o f t h e o v e r v i e w 0 to t o t a l s i z e o f all v i e w s  O+F+C  (0 for i n t e r f a c e s w i t h o u t a n o v e r v i e w ) .  A s p r e v i o u s l y m e n t i o n e d , e a c h i n t e r f a c e a l w a y s p r o v i d e d a t o t a l of 6 0 0 . 0 0 0 p i x e l s o f i n f o r m a t i o n in a l l v i e w s .  In i n t e r f a c e s w i t h o u t o v e r v i e w s , t h i s a m o u n t  Chapter 4. Study 1  33  0  c c  F  c  c  F  c  C F i g u r e 4.6: C a l c u l a t i o n of levels o f c o n t e x t i n S t u d y 1 R S N interfaces.  Level of  n a v i g a t i o n a l c o n t e x t is t h e f r a c t i o n o f t h e s i z e o f t h e p e r i p h e r a l c o n t e x t a r e a s t o t h e t o t a l s i z e o f t h e d e t a i l v i e w F+C. o f t h e size o f t h e o v e r v i e w  O to  C  L e v e l o f o v e r v i e w c o n t e x t is t h e f r a c t i o n  the t o t a l size of all views  O+F+C.  0  f F i g u r e 4.7:  F  C a l c u l a t i o n o f levels of c o n t e x t  in Study  )l  1 P Z N interfaces.  The  d o t t e d l i n e i n d i c a t e s t h e b o u n d a r y b e t w e e n f o c u s a n d c o n t e x t r e g i o n s , w h i c h is not v i s u a l l y d e m a r c a t e d in the interfaces. c o n t e x t a r e as i n F i g u r e 4 . 6 .  Levels of navigational a n d overview  Chapter 4. Study 1 was equal to Thus,  F+C.  as s h o w n  34  w h i l e i n i n t e r f a c e s w i t h o v e r v i e w s , it w a s e q u a l t o  i n F i g u r e s 4.1  t o 4.4,  interfaces  without  overviews  O+F+C. provided  larger d e t a i l views t h a n their c o u n t e r p a r t s w i t h overviews, b u t the level of navi g a t i o n a l c o n t e x t w a s k e p t c o n s t a n t for e a c h n a v i g a t i o n t e c h n i q u e , r e g a r d l e s s o f the presence of a n overview.  4.2.4 As  RSN-NoOV  Interface  i l l u s t r a t e d i n F i g u r e 4.1, t h i s i n t e r f a c e h a d n o o v e r v i e w a n d a l l o w e d  users  to n a v i g a t e the d a t a s e t using the m e t a p h o r of e x p a n d i n g a n d c o m p r e s s i n g a r u b b e r sheet w i t h  its b o r d e r s n a i l e d d o w n .  U n l i k e in c o n v e n t i o n a l p a n a n d  z o o m i n t e r f a c e s , n a v i g a t i o n a c t i o n s d i d not, p u s h c o n t e x t r e g i o n s o f f - s c r e e n , b u t compressed  them  in the p e r i p h e r y o f the view,  where they remained visually  salient.  F o c u s r e g i o n s were d e m a r c a t e d b y c o l o r e d b o x e s ,  located  in t h e  center  o f the  view.  w h i c h were  always  U s e r s c o u l d select, a r e c t a n g u l a r a r e a o f  i n t e r e s t for z o o m i n g i n b y d r a g g i n g out. a b o x w i t h t h e left m o u s e b u t t o n .  The  c o n t e n t s o f t h e s e l e c t e d a r e a t h e n e x p a n d e d to fill o n e o f t h e t w o f o c u s r e g i o n s i n a, s m o o t h t r a n s i t i o n . B y d e f a u l t , t h e s y s t e m filled t h e f o c u s w h o s e c e n t r o i d was c l o s e r t o t h e c e n t r o i d o f the s e l e c t e d a r e a o f i n t e r e s t .  U s e r s c o u l d also  w h i c h focus r e g i o n was to be filled b y p r e s s i n g a m o d i f i e r key.  specify  T h e Shift key  w a s u s e d to s p e c i f y t h e t o p focus a n d t h e C t r l key for t h e b o t t o m f o c u s .  These  k e y s were c h o s e n b e c a u s e o f t h e i r p o s i t i o n o n e a b o v e t h e o t h e r o n t h e k e y b o a r d , w h i c h h e l p e d users a s s o c i a t e t h e m w i t h t h e r e s p e c t i v e f o c i . A n a c t i o n a n a l o g o u s to p a n n i n g w a s a c c o m p l i s h e d v i a h o r i z o n t a l a n d v e r t i c a l d r a g m o t i o n s w i t h right mouse  b u t t o n , allowing users to fine-tune  focus r e g i o n s e l e c t i o n s .  the  Users  c o u l d z o o m out. b y d r a g g i n g o u t a r e c t i l i n e a r r e g i o n l a r g e r t h a n t h e f o c u s r e g i o n , t h e c o n t e n t s of w h i c h were t h e n c o m p r e s s e d to fill t h e f o c u s r e g i o n .  4.2.5  PZN-NoOV  Interface  A s i l l u s t r a t e d in F i g u r e 4.2, t h i s i n t e r f a c e h a d n o o v e r v i e w a n d a l l o w e d to n a v i g a t e  using conventional p a n and z o o m interactions.  users  Just, as w i t h  the  Chapter 4. Study 1 RSN-NoOV  35  i n t e r f a c e , u s e r s s e l e c t e d a r e c t a n g u l a r a r e a o f i n t e r e s t for z o o m i n g  in w i t h a left m o u s e d r a g , r e s u l t i n g in a n a n i m a t e d t r a n s i t i o n t h a t filled  the focus w i t h the selected area.  completely  S i m i l a r l y to the R S N - N o O V  interface,  b y d e f a u l t t h e s y s t e m filled t h e f o c u s w h o s e c e n t r o i d w a s c l o s e r to t h e c e n t r o i d o f t h e s e l e c t e d a r e a o f i n t e r e s t , b u t users c o u l d a l s o s p e c i f y w h i c h f o c u s w a s b e filled b y p r e s s i n g t h e S h i f t o r C t r l m o d i f i e r key. focus selection  Users could  fine-tune  to the  by p a n n i n g w i t h h o r i z o n t a l a n d v e r t i c a l r i g h t - m o u s e d r a g s , a n d  gradually z o o m out with vertical middle-mouse drags.  W h e n marked  regions  m o v e d off-screen d u e to n a v i g a t i o n a c t i o n s , c o l o r e d H a l o - l i k e a r c s , r e p r e s e n t i n g the visible p a r t s of e l l i p t i c a l r i n g s centered o n the m a r k e d regions, a p p e a r e d in c o n t e x t a r e a s at t h e p e r i p h e r y o f t h e i n t e r f a c e . T h e a r c s i n d i c a t e d d i r e c t i o n a n d d i s t a n c e to m a r k e d r e g i o n s , a n d d i s a p p e a r e d o n c e t h e m a r k e d r e g i o n s visible on-screen. areas in this  U n l i k e in the  interface  RSN-NoOV  interface,  were oval rather than  became  the p e r i p h e r a l c o n t e x t  r e c t a n g u l a r in shape,  were  not  v i s u a l l y d e l i m i t e d , a n d d i d n o t c h a n g e in t e r m s o f r e s o l u t i o n .  4.2.6  R S N + O V Interface  F i g u r e 4.3  illustrates that this interface used the s a m e n a v i g a t i o n controls  the R S N - N o O V of view The  interface.  It a l s o h a d a n o v e r v i e w  boxes corresponding to  size a n d l o c a t i o n o f t h e  the extent  field  NoOV  focus  two c o l o r e d  in the  detail  field view.  of view boxes were u p d a t e d d y n a m i c a l l y  n a v i g a t i o n t o o k p l a c e in t h e d e t a i l v i e w . navigation equivalents  of each  showing  as  Users c o u l d p e r f o r m the r u b b e r sheet  o f p a n n i n g a n d z o o m i n g , as i m p l e m e n t e d  interface, directly in the overview  as  b y d r a g g i n g the  field  in the R S N -  of view  boxes,  w h i c h t h e n u p d a t e d t h e a p p r o p r i a t e foci in t h e d e t a i l v i e w .  4.2.7  PZN+OV  F i g u r e 4.4  illustrates  Interface that, t h i s  interface h a d the  t h e P Z N - N o O V i n t e r f a c e , as w e l l as a n o v e r v i e w .  same navigation controls J u s t as w i t h t h e  as  RSN+OV  i n t e r f a c e , t h e field o f v i e w b o x e s i n the o v e r v i e w d y n a m i c a l l y r e f l e c t e d n a v i g a t i o n  Chapter 4. Study 1  36  in t h e d e t a i l v i e w a n d c o u l d b e m a n i p u l a t e d d i r e c t l y to c o n t r o l t h e foci i n t h e detail view.  4.3  Task and Dataset  T h e t a s k u s e d i n the e x p e r i m e n t w a s a tree t o p o l o g i c a l t a s k t h a t r e q u i r e d s u b jects to c o m p a r e t o p o l o g i c a l distances  between colored n o d e s in a large  tree  dataset a n d determine w h i c h of the distances was smaller. T a s k a n d dataset are b o t h d e s c r i b e d in d e t a i l i n C h a p t e r 3.  4.4  Apparatus  T h e s t u d y was c o n d u c t e d o n two systems r u n n i n g W i n d o w s X P w i t h P e n t i u m 4 p r o c e s s o r s . 2.0 G B R A M .  N v i d i a G e F o r c e 2 v i d e o c a r d s , a n d 19 i n c h  moni-  t o r s c o n f i g u r e d at a r e s o l u t i o n o f 1 2 8 0 x 1 0 2 4 p i x e l s . T h e e x p e r i m e n t a l s o f t w a r e , i n c l u d i n g t h e i n t e r f a c e s , w a s f u l l y a u t o m a t e d a n d w a s c o d e d i n J a v a 1.4.2 O p e n G L u s i n g the S w i n g a n d G L 4 J a v a  4.5  and  libraries.  Participants  F o r t y s u b j e c t s (15 f e m a l e ) b e t w e e n 18 a n d 39 y e a r s o f age s u c c e s s f u l l y c o m p l e t e d t h e s t u d y a n d were e a c h c o m p e n s a t e d S10 for t h e i r p a r t i c i p a t i o n . A l l s u b j e c t s were r i g h t - h a n d e d , h a d n o r m a l  o r c o r r e c t e d t o n o r m a l v i s i o n , a n d were  not  c o l o r b l i n d . T h e y were r e c r u i t e d t h r o u g h a d v e r t i s e m e n t s p o s t e d t h r o u g h o u t t h e university c a m p u s and t h r o u g h an online participant scheduling system. O r i g i n a l l y . 45 s u b j e c t s p a r t i c i p a t e d i n t h e e x p e r i m e n t .  O n e of the  subjects  was u n a b l e t o follow the t r a i n i n g i n s t r u c t i o n s s u c c e s s f u l l y , w h i l e a n o t h e r was n o t s u c c e s s f u l i n l e a r n i n g to use t h e m o u s e s c r o l l w h e e l , r e q u i r e d t o p e r f o r m z o o m i n g out i n t h e p a n a n d z o o m i n t e r f a c e s . T h r e e o t h e r s f o l l o w e d t h e i n s t r u c t i o n s b u t c o m m i t t e d t h r e e o r m o r e e r r o r s (an e r r o r r a t e g r e a t e r t h a n 10%).  These  five  Chapter 4. Study 1  37  Order  Block 1  Block 2  Block 3  Block 4  Block 5  1  3  1  5  2  '4  2  4  3  1  5  2  3  2  4  3  1  5  4  5  2  4  3  1  5  1  5  2  4  3  T a b l e 4.2:  L a t i n s q u a r e u s e d to c o u n t e r b a l a n c e t h e o r d e r o f p r e s e n t a t i o n  for  level o f c o n t e x t .  s u b j e c t s w e r e t r e a t e d as o u t l i e r s for t h e p u r p o s e o f d a t a a n a l y s i s , l e a v i n g a t o t a l of 40 d a t a points.  4.6 The  Design e v a l u a t i o n u s e d a. 4 ( i n t e r f a c e ,  within subjects)  between  subjects)  d e s i g n , w h e r e e a c h level o f c o n t e x t  c o n t a i n i n g 5 trials.  b y 5 (level o f  context,  c o r r e s p o n d e d to a b l o c k  N a v i g a t i o n technique a n d presence of overview were  not  e x a m i n e d as s e p a r a t e f a c t o r s i n t h i s s t u d y d u e t o t h e i n t e r f a c e - s p e c i f i c v a r i a t i o n o f l e v e l s o f c o n t e x t a n d o v e r v i e w sizes.  I n t e r f a c e w a s c h o s e n to b e a  between-  s u b j e c t s f a c t o r d u e to t h e p o s s i b i l i t y o f t r a n s f e r effects o f n a v i g a t i o n t e c h n i q u e in a w i t h i n - s u b j e c t s d e s i g n , as well as t h e t i m e r e q u i r e d to t r a i n s u b j e c t s n a v i g a t i o n with each technique. the four interfaces.  on  S u b j e c t s were r a n d o m l y a s s i g n e d t o e a c h o f  L e v e l o f c o n t e x t w a s c h o s e n to b e a w i t h i n - s u b j e c t s f a c t o r  to allow c o m p a r i s o n between  t h e d i f f e r e n t levels o f context, for e a c h i n t e r f a c e .  T o m i n i m i z e o r d e r i n g effects, we c o u n t e r b a l a n c e d t h e o l d e r o f p r e s e n t a t i o n for level o f c o n t e x t  u s i n g a L a t i n s q u a r e , as s h o w n i n T a b l e  4.2.  In o r d e r to d e t e r m i n e t h e r a n g e o f levels o f c o n t e x t t o b e u s e d in t h e s t u d y , we p i l o t e d e a c h e x p e r i m e n t a l i n t e r f a c e w i t h 5 to 9 s u b j e c t s u s i n g t h e e x p e r i m e n t a l task a n d dataset. for  T h e levels o f c o n t e x t u s e d in p i l o t i n g v a r i e d f r o m 10% to 9 5 %  n a v i g a t i o n a l c o n t e x t a n d f r o m 5% t o 50% for o v e r v i e w c o n t e x t .  Based on  Chapter 4. Study 1 Interface  38  Level of  Level of  Navigational Context RSN-NoOV  40  PZN-NoOV  30,  ;  Overview  50,  60,  70, 8 0  0  40,  50, 6 0 , 70  0  Context  RSN+OV  60  5,  10,  15, 20, 25  PZN+OV  50  5,  10,  15, 20, 25  T a b l e 4.3: L e v e l s o f c o n t e x t u s e d for e a c h i n t e r f a c e , i n p e r c e n t . B o l d f a c e d e n o t e s v a l u e s e x p e c t e d to r e s u l t i n o p t i m a l p e r f o r m a n c e for e a c h i n t e r f a c e b a s e d o n p i l o t results.  T h e level o f c o n t e x t  i n the d e t a i l v i e w o f i n t e r f a c e s w i t h a n o v e r v i e w  was set t o t h e m i d d l e level o f c o n t e x t u s e d for t h e i r c o u n t e r p a r t s w i t h o u t  an  overview.  p i l o t r e s u l t s , we s e l e c t e d a r a n g e o f five l e v e l s o f c o n t e x t for e a c h i n t e r f a c e t h a t p e r f o r m e d best in t e r m s of c o m p l e t i o n times.  T h e levels o f c o n t e x t u s e d i n e a c h  i n t e r f a c e a r e l i s t e d i n T a b l e 4.3, w i t h t h e l e v e l s o f c o n t e x t e x p e c t e d t o p e r f o r m b e s t for e a c h i n t e r f a c e b a s e d o n p i l o t r e s u l t s s h o w n i n b o l d .  4.7 Procedure T h e e x p e r i m e n t w a s d e s i g n e d to fit i n t o a s i n g l e 60 m i n u t e s e s s i o n .  T h e experi-  m e n t e r first i n s t r u c t e d s u b j e c t s o n t h e use o f t h e different n a v i g a t i o n t e c h n i q u e s a f f o r d e d b y t h e i n t e r f a c e to w h i c h t h e y h a d b e e n r a n d o m l y a s s i g n e d .  Subjects  were t h e n s h o w n t h e e x p e r i m e n t a l t a s k a n d i n s t r u c t e d t h a t t h e y w e r e t o t a k e as m u c h t i m e as n e c e s s a r y t o s o l v e it c o r r e c t l y w h i l e m a x i m i z i n g t h e i r efficiency. The  e x p e r i m e n t e r t h e n t r a i n e d s u b j e c t s o n t h e use o f l o n g , t h i n h o r i z o n t a l se-  lection areas to c o m p l e t e  the task.  T h i s strategy  h a d been found to i m p r o v e  t a s k c o m p l e t i o n t i m e i n a l l interfaces i n p i l o t i n g . S i n c e m a n y o f t h e p a t h s b e tween  colored nodes  were h o r i z o n t a l , this strategy  them r a p i d l y into focus.  enabled subjects  to  bring  S u b j e c t s were t h e n g i v e n a t r a i n i n g b l o c k o f 5 t r i a l s .  D u r i n g these trials, s u b j e c t s p e r f o r m e d the task on their o w n . a n d the e x p e r i -  Chapter 4. Study 1  39  m e n t e r r e m i n d e d s u b j e c t s o f t h e t r a i n i n g s t r a t e g y as n e e d e d .  F o r the t r a i n i n g  b l o c k , t h e m i d d l e level o f c o n t e x t v a l u e o f t h o s e s h o w n i n T a b l e 4.3 w a s  used  for e a c h i n t e r f a c e . A t t h e e n d o f t h e t r a i n i n g session, s u b j e c t s w e r e g i v e n a o n e minute break.  After the break, the experimenter exited  the r o o m where  e x p e r i m e n t was c o n d u c t e d , a n d s u b j e c t s p r o c e e d e d w i t h the e x p e r i m e n t .  the The  c o m p l e t e t r a i n i n g p r o t o c o l for t h i s s t u d y c a n b e f o u n d i n A p p e n d i x A . In t h e e x p e r i m e n t , s u b j e c t s w e r e p r e s e n t e d w i t h 5 b l o c k s , e a c h c o n t a i n i n g 5 t r i a l s , for a t o t a l o f 25 t r i a l s . A l l s u b j e c t s w e r e p r e s e n t e d w i t h a n i d e n t i c a l set o f questions, w i t h a p r e d e t e r m i n e d g r o u p i n g of questions into blocks. T h e order of b l o c k s w a s d e t e r m i n e d u s i n g t h e L a t i n s q u a r e s h o w n i n T a b l e 4.2. T h e b l o c k s o f questions were verified to be i s o m o r p h i c in difficulty in p i l o t i n g . S u b j e c t s were given a one minute break between each block of questions. A t the e n d of the e x p e r i m e n t , subjects c o m p l e t e d q u e s t i o n n a i r e s , w h i c h c a n b e f o u n d i n A p p e n d i x C . T h e q u e s t i o n n a i r e s were u s e d to c o l l e c t i n f o r m a t i o n a b o u t the subjects' d e m o g r a p h i c b a c k g r o u n d a n d c o m p u t e r usage.  They  also  i n c l u d e d r a t i n g s for ease o f use, ease o f n a v i g a t i o n , a n d i n t e r f a c e - s p e c i f i c f e a t u r e s o n 5 - p o i n t L i k e r t scales.  S p a c e w a s a l s o p r o v i d e d for s u b j e c t s to c o m m e n t o n  t h e i r e x p e r i e n c e s w i t h t h e i n t e r f a c e s a n d p r o v i d e s u g g e s t i o n s for i m p r o v e m e n t . Short informal interviews were c o n d u c t e d with some of the subjects based on their q u e s t i o n n a i r e responses.  4.8  Measures  O u r p e r f o r m a n c e measures were based o n logged d a t a a n d i n c l u d e d task c o m pletion  times  and errors.  Additionally,  through the post-experiment tion.  self-reported measures  were  collected  q u e s t i o n n a i r e , as d e s c r i b e d i n t h e p r e v i o u s sec-  T h e s t u d y was d e s i g n e d to m i n i m i z e e r r o r s , w i t h t a s k c o m p l e t i o n  u s e d as t h e p r i m a r y m e a s u r e o f p e r f o r m a n c e .  times  40  Chapter 4. Study 1 4.9  Results  T h i s section presents the e x p e r i m e n t a l results, r e p o r t i n g in detail o n the r e l a t e d t o effects o f l e a r n i n g a n d n a v i g a t i o n t e c h n i q u e .  results  T h e r e s u l t s for p r e s e n c e  of o v e r v i e w are s u m m a r i z e d here, a n d details o n these c a n b e f o u n d i n B o d n a r ' s m a s t e r ' s t h e s i s [12]. P r i o r to analysis, o u t l i e r d a t a l y i n g m o r e t h a n 3 s t a n d a r d d e v i a t i o n s the  means  of each  experimental  cell w e r e r e m o v e d  from  the  from  analysis.  The  G r e e n h o u s e - G e i s s e r a d j u s t m e n t w a s u s e d for n o n - s p h e r i c a l d a t a , a n d t h e B o n f e r r o n i a d j u s t m e n t for p o s t - h o c c o m p a r i s o n s . A l o n g w i t h s t a t i s t i c a l we r e p o r t p a r t i a l e t a - s q u a r e d (n ), 2  significance,  a m e a s u r e o f effect, size, w h i c h is o f t e n  more  informative t h a n statistical significance in a p p l i e d h u m a n - c o m p u t e r i n t e r a c t i o n r e s e a r c h [32].  T o i n t e r p r e t t h i s v a l u e , .01 is a s m a l l effect size, .06 is m e d i u m ,  a n d .14 is l a r g e  [17].  T h e o v e r a l l r e s u l t s for m e a n c o m p l e t i o n t i m e s p e r t r i a l a r e i l l u s t r a t e d i n F i g u r e 4.8.  A o n e - w a y A N O V A w a s r u n t o u n d e r s t a n d t h e effect o f i n t e r f a c e ,  of c o n t e x t , a n d b l o c k o n c o m p l e t i o n t i m e .  A s expected,  level  performance improved  as s u b j e c t s p r o g r e s s e d t h r o u g h t h e e x p e r i m e n t , w i t h a s i g n i f i c a n t m a i n effect o f b l o c k (_F(4,144) =  12.309, p <  .001, if  m a i n effect o f i n t e r f a c e o n c o m p l e t i o n  = time  -255).  T h e r e was also a  (F(3,36)  =  significant  2.924, p <  .05, rj  2  .196), b u t p o s t - h o c c o m p a r i s o n s r e v e a l e d n o s i g n i f i c a n t p a i r w i s e d i f f e r e n c e s tween interfaces. was  N o significant, i n t e r a c t i o n effect b e t w e e n b l o c k a n d  = be-  interface  present. O n e - w a y A N O V A s w e r e p e r f o r m e d t o i n v e s t i g a t e t h e effect o f level o f c o n t e x t  on completion  t i m e s for e a c h i n t e r f a c e .  A s shown  in T a b l e 4.4,  there was  no  s i g n i f i c a n t effect, o f level o f c o n t e x t for a n y o f t h e i n t e r f a c e s , d e s p i t e h i g h effect, sizes for t h r e e o f t h e f o u r i n t e r f a c e s .  T h e best mean p e r f o r m a n c e w i t h the R S N -  N o O V a n d P Z N - N o O V i n t e r f a c e s o c c u r r e d w i t h c o n t e x t levels o f 50% a n d 40%,, respectively, PZN+OV  while  the  best, m e a n  performance with both  the  i n t e r f a c e s o c c u r r e d w i t h a u o v e r v i e w size o f 15%.  t i m e s for e a c h i n t e r f a c e a r e s h o w n i n F i g u r e s 4.9 t h r o u g h 4.12.  RSN+OV  Mean  and  completion  Separate  figures  Chapter 4. Study 1  41  RSN-NoON PZN-NoOV •Mr RSN+OV PZN+OV  20 10 0 1  F i g u r e 4.8:  2  3 Block  4  5  M e a n p e r - t r i a l c o m p l e t i o n t i m e s b y i n t e r f a c e for b l o c k s 1-5, i n sec-  onds (JV=40).  Interface R S N - N o O V  T a b l e 4.4:  df 1.826,  16.43  Partial  F  Sig.  1.272  .303  .124  P Z N - N o O V  4,36  .456  .767  .048  R S N + O V  4,36  1.380  .260  .133  P Z N + O V  4,36  1.480  .229  .141  rj  2  R e s u l t s of f o u r o n e - w a y A N O V A s i n v e s t i g a t i n g t h e effect o f l e v e l o f  c o n t e x t o n c o m p l e t i o n t i m e , b y interface ( J V = 1 0 ) . i n t e r f a c e a r e a d j u s t e d for s p h e r i c i t y .  R e s u l t s for t h e  RSN-NoOV  Chapter 4. Study 1  42  are u s e d t o r e p o r t t h e s e r e s u l t s d u e t o t h e differences b e t w e e n r a n g e s o f levels o f c o n t e x t e x a m i n e d for e a c h interface. C o u n t e r t o o u r h y p o t h e s i s H I , t h e r e w a s n o s i g n i f i c a n t difference  between  p e r f o r m a n c e w i t h m i d d l e a n d e x t r e m e levels o f c o n t e x t for e i t h e r R S N o r P Z N . F i g u r e s 4.9  t h r o u g h 4.10  t r e n d for t h i s h y p o t h e s i s nique. H2,  illustrate that  the  was n o t p r e s e n t  S i m i l a r l y , F i g u r e s 4.11  a n d 4.12  expected  U-shaped  performance  i n d a t a for e i t h e r n a v i g a t i o n  show that, counter to our  tech-  hypothesis  t h e r e was n o s i g n i f i c a n t difference b e t w e e n p e r f o r m a n c e w i t h m i d d l e a n d  e x t r e m e o v e r v i e w sizes for e i t h e r R S N o r P Z N interfaces w i t h o v e r v i e w s .  The  i m p l i c a t i o n s o f t h i s f i n d i n g a r e d i s c u s s e d i n d e t a i l i n B o d n a r ' s thesis [12]. On  a v e r a g e , s u b j e c t s c o m m i t t e d 0.75 e r r o r s o v e r t h e c o u r s e o f t h e e x p e r i -  m e n t , for a m e a n e r r o r r a t e o f 3.0%.  T h e r e were n o s i g n i f i c a n t m a i n o r i n t e r a c -  t i o n effects o f i n t e r f a c e o r l e v e l o f c o n t e x t o n e r r o r r a t e .  4.10 We  RI:  Summary of Results  s u m m a r i z e o u r r e s u l t s a c c o r d i n g t o t h e h y p o t h e s e s s t a t e d i n S e c t i o n 4.1:  F o r b o t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n , m e d i u m levels o f c o n t e x t d i d n o t p e r f o r m b e t t e r t h a n l o w o r h i g h levels.  R2:  F o r b o t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n , i n i n t e r f a c e s  with  o v e r v i e w s , m e d i u m o v e r v i e w sizes d i d n o t p e r f o r m b e t t e r t h a n l o w o r h i g h ones.  The  best p e r f o r m a n c e in terms of m e a n c o m p l e t i o n times o c c u r r e d w i t h a  c o n t e x t l e v e l o f 50% i n t h e R S N - N o O V i n t e r f a c e , a c o n t e x t l e v e l o f 40% i n t h e PZN-NoOV PZN+OV  interface,  interfaces.  a n d overview  sizes o f 15% i n b o t h t h e  RSN+OV  and  Chapter 4. Study 1  43  30 20 10 -  o\  1  1  30  40  50  1— 60  —. 70  1— 80  1  90  Level of context (%)  F i g u r e 4.9: M e a n p e r - t r i a l c o m p l e t i o n t i m e s ( d a r k l i n e ) a n d q u a d r a t i c t r e n d l i n e (light l i n e ) for t h e R S N - N o O V i n t e r f a c e , i n s e c o n d s  F i g u r e 4.10:  (N=10).  M e a n p e r - t r i a l c o m p l e t i o n times ( d a r k line) a n d q u a d r a t i c t r e n d  l i n e ( l i g h t l i n e ) for t h e P Z N - N o O V interface, i n s e c o n d s ( J V = 1 0 ) .  Chapter 4. Study 1  44  100  30 20 10 0 0  5  10  15  20  25  30  Level of context (%)  F i g u r e 4.11:  M e a n p e r - t r i a l c o m p l e t i o n times ( d a r k line) a n d q u a d r a t i c t r e n d  l i n e ( l i g h t line) for t h e R S N + O V interface, i n s e c o n d s  F i g u r e 4.12:  (N=W).  M e a n p e r - t r i a l c o m p l e t i o n times ( d a r k line) a n d q u a d r a t i c t r e n d  line ( l i g h t l i n e ) for t h e P Z N + O V i n t e r f a c e , i n s e c o n d s  (JV=10).  Chapter 4. Study 1  4.11  45  Strategies  In o r d e r to g a i n a better u n d e r s t a n d i n g of w h y level of context d i d not signific a n t l y affect c o m p l e t i o n t i m e s , we e x a m i n e d l o g g e d n a v i g a t i o n a n d reset a c t i o n data.  Although  the l o g g i n g format used in this s t u d y was not  conducive  to  a s t a t i s t i c a l a n a l y s i s o f t h e s e d a t a , a m a n u a l a n a l y s i s o f n a v i g a t i o n a n d reset, p a t t e r n s for i n d i v i d u a l s u b j e c t s s h o w e d t h a t , for e a c h i n t e r f a c e , m o s t consistently used a s m a l l n u m b e r of well-defined strategies periment.  S o m e of these strategies  subjects  t h r o u g h o u t the  were r e l a t e d to n a v i g a t i o n p a t t e r n s ,  ex-  while  o t h e r s i n v o l v e d d i f f e r e n t w a y s o f u s i n g o v e r v i e w s o r c o m p e n s a t i n g for t h e a b sence of overviews b y m e a n s of u s i n g the reset f u n c t i o n . T h e strategies  related  to n a v i g a t i o n a r e d e t a i l e d in T a b l e 4.5. w h i l e t h o s e r e l a t e d to o v e r v i e w a n d reset u s a g e a r e d i s c u s s e d in B o d n a r s thesis [12]. B a s e d o n t h e m a n u a l a n a l y s i s o f l o g d a t a , we g r o u p e d s u b j e c t s w h o u s e d t h e RSN-NoOV,  PZN-NoOV,  navigation strategy.  and R S N + O V  interfaces a c c o r d i n g to their p r i m a r y  O n e - w a y A N O V A s w e r e t h e n p e r f o r m e d for e a c h i n t e r f a c e  t o u n d e r s t a n d t h e effect o f n a v i g a t i o n s t r a t e g y o n c o m p l e t i o n t i m e . of the R S N interfaces, the  For both  "zoom, then p a n " s t r a t e g y resulted in faster  c o m p l e t i o n t i m e s t h a n t h e " z o o m o n l y " s t r a t e g y (67.9 s e c o n d s v s . 75.7 for R S N - N o O V ;  63.8 s e c o n d s  vs.  75.6 s e c o n d s  for R S N + O V ) .  d i f f e r e n c e w a s not, s t a t i s t i c a l l y s i g n i f i c a n t for R S N - N o O V >  .2, if  =  3.008, p <  =  seconds  Although  (F(2.47)  .033), a n d o n l y b o r d e r l i n e s i g n i f i c a n t for t h e R S N + O V .09. if  mean  =  this  1.616,  (F(2,47)  .059), these results s u g g e s t e d the i m p o r t a n c e of the  p =  use  o f t h e r u b b e r s h e e t e q u i v a l e n t , o f p a n n i n g for effective n a v i g a t i o n , a n d led us t o e m p h a s i z e t h e use o f t h i s o p e r a t i o n i n t h e t r a i n i n g p r o t o c o l o f S t u d y 2. F o r t h e P Z N - N o O V i n t e r f a c e , the t h r e e s t r a t e g i e s were s i g n i f i c a n t l y different in t e r m s o f c o m p l e t i o n t i m e ( F ( 2 . 4 7 )  =  9.226, p <  .001, if  =  .282).  Post-hoc  p a i r w i s e c o m p a r i s o n s s h o w e d t h a t the " z o o m i n , t h e n p a n " s t r a t e g y w a s s i g n i f i c a n t l y s l o w e r (p < the  .01) t h a n b o t h the " z o o m i n . t h e n z o o m o u t " s t r a t e g y a n d  "overview " s t r a t e g y 7  (mean completion times:  104.2 s e c o n d s . 80.0  seconds,  a n d 75.4 s e c o n d s , r e s p e c t i v e l y ) . T h i s f i n d i n g m o t i v a t e d us t o p r o v i d e a d e t a i l e d  Chapter 4. Study 1  Interface R S N - N o O V  Description  Strategy Zoom only  (N=6)  Z o o m , then pan P Z N - N o O V  46  U s e R S N z o o m only. (N=4)  Use R S N z o o m and pan.  Z o o m in. then pan  Z o o m into n e i g h b o u r h o o d  (N=4)  of a m a r k e d n o d e ,  then  follow p a t h b y p a n n i n g . Z o o m in. then  Z o o m into n e i g h b o u r h o o d  zoom out  of a m a r k e d node,  (N—4)  then  z o o m out to reveal p a t h .  R S N + O V  Overview  Z o o m in w i t h o n e focus,  (N=2)  use t h e o t h e r a s o v e r v i e w .  Z o o m only  P Z N + O V  Use R S N z o o m only.  (N=6)  Zoom, then pan  then  (N=4)  Use R S N zoom and pan.  None  T a b l e 4.5: S t r a t e g i e s r e l a t e d t o n a v i g a t i o n d e v e l o p e d b y s u b j e c t s in S t u d y 1.  t r a i n i n g s t r a t e g y for t h e P Z N - N o O V i n t e r f a c e i n S t u d y 2.  4.12  Discussion  R e s u l t s o f t h i s s t u d y s h o w t h a t level o f c o n t e x t d i d n o t s i g n i f i c a n t l y affect p e r f o r m a n c e as m e a s u r e d b y c o m p l e t i o n t i m e s w i t h e i t h e r p a n a n d z o o m o r r u b b e r sheet  navigation.  Also,  the  expected  U-shape  of the  completion  time.data,  i n d i c a t i n g s u p e r i o r p e r f o r m a n c e o n m e d i u m r a t h e r t h a n h i g h o r low levels o f context, was not present.  T h i s f i n d i n g s e e m s s u r p r i s i n g s i n c e , for b o t h n a v i g a -  t i o n t e c h n i q u e s , we e x a m i n e d a r a n g e o f levels o f context, s p a n n i n g a s i g n i f i c a n t p r o p o r t i o n o f the a v a i l a b l e s c r e e n real e s t a t e . It is p o s s i b l e t h a t o u r s t u d y d e s i g n d i d not p r o v i d e sufficient p o w e r to detect, differences w i t h i n t h e r a n g e s for e a c h interface.  T h i s e x p l a n a t i o n w o u l d a c c o u n t for t h e m e d i u m t o h i g h effect sizes  o f level o f c o n t e x t in a l l i n t e r f a c e s , as s h o w n in T a b l e 4.4.  Chapter 4. Study 1  47  A n o t h e r p o s s i b i l i t y is t h a t t h e r a n g e s we e x a m i n e d were s t i l l n o t s u f f i c i e n t l y large to significantly i m p a c t the way subjects  navigated.  T h i s p o s s i b i l i t y is  s u p p o r t e d b y qualitative feedback f r o m questionnaires a n d follow-up interviews w i t h the subjects.  O n l y o n e s u b j e c t c o m m e n t e d o n t h e difference b e t w e e n s m a l l  a n d l a r g e levels o f c o n t e x t , a n d a n u m b e r o f s u b j e c t s s t a t e d t h a t t h e y were n o t even aware of the changes i n level of context d u r i n g the e x p e r i m e n t . W e therefore h y p o t h e s i z e  that,  for b o t h p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n ,  the range of levels of context  c o n d u c i v e t o effective  n a v i g a t i o n is  sufficiently  b r o a d t o e n c o m p a s s t h e r a n g e e x a m i n e d i n o u r e x p e r i m e n t , a n d t h a t differences b e t w e e n levels o f c o n t e x t w i t h i n t h i s r a n g e d o n o t s i g n i f i c a n t l y i m p a c t p e r f o r mance.  T h u s , for e a c h n a v i g a t i o n t e c h n i q u e , t h e r e m a y n o t e x i s t a n o p t i m a l  l e v e l o f c o n t e x t v a l u e for p e r f o r m i n g a g i v e n t a s k , b u t r a t h e r u p p e r a n d l o w e r b o u n d s b e y o n d w h i c h performance deteriorates, similar to the b o u n d s that have b e e n p r o p o s e d for o v e r v i e w sizes [41]. It is also p o s s i b l e t h a t t h e effect o f l e v e l o f context o n n a v i g a t i o n p e r f o r m a n c e can be represented b y a discontinuous value function.  In p a r t i c u l a r , a s m a l l a m o u n t of context m a y i m p r o v e p e r f o r m a n c e  c o m p a r e d t o z e r o c o n t e x t , w i t h f u r t h e r increases p r o v i d i n g n o a d d e d F o r three of the  four i n t e r f a c e s e x a m i n e d  in this experiment,  benefits. navigation  s t r a t e g i e s u s e d b y t h e s u b j e c t s h a d a n o t i c e a b l e effect o n p e r f o r m a n c e . In t h e R S N i n t e r f a c e s , t h e t w o s t r a t e g i e s d i f f e r e d o n l y i n w h e t h e r s u b j e c t s chose t o use t h e r u b b e r sheet e q u i v a l e n t o f p a n n i n g or to r e l y s o l e l y o n r u b b e r sheet z o o m i n g a c t i o n s . T h i s difference l i k e l y r e s u l t e d f r o m t h e fact t h a t t h e n a v i g a t i o n s t r a t e g y u s e d i n t r a i n i n g ( t h e use o f l o n g , t h i n h o r i z o n t a l s e l e c t i o n areas) o n l y i n v o l v e d zooming, a n d , although subjects  were s h o w n h o w t o p a n , t h e use o f p a n n i n g  was left to t h e i r d i s c r e t i o n . P e r h a p s m o r e s u r p r i s i n g was the d e v e l o p m e n t of three distinct n a v i g a t i o n strategies w i t h the P Z N - N o O V interface. T h i s finding c a n b e e x p l a i n e d b y noti n g t h a t t h i s i n t e r f a c e c o n t a i n e d two focus areas o f t h e s a m e size a n d r e s o l u t i o n , providing subjects  w i t h the options of using one view exclusively,  alternating  between the focus areas d e p e n d i n g o n the location of the m a r k e d nodes, or using o n e f o c u s as a d e t a i l v i e w a n d a n o t h e r as a n o v e r v i e w . F u r t h e r m o r e , t h e d i s t i n c -  Chapter 4. Study 1  48  t i o n between the "zoom i n , then p a n " a n d "zoom i n , t h e n z o o m out" strategies c a n b e a t t r i b u t e d t o t h e fact t h a t z o o m o u t , like p a n , w a s n o t s p e c i f i c a l l y c o v e r e d b y t h e t r a i n i n g s t r a t e g y u s e d i n t h e s t u d y . T h e s i g n i f i c a n t l y slower p e r f o r m a n c e o f s u b j e c t s u s i n g t h e " z o o m i n , t h e n p a n " p o i n t s to t h e i n e f f i c i e n c y o f p a n n i n g at a h i g h m a g n i f i c a t i o n l e v e l , c o n s i s t e n t  w i t h results of previous studies  T h e l a c k o f s i g n i f i c a n t difference i n p e r f o r m a n c e b e t w e e n t h e  [46].  "overview"  and  "zoom i n , t h e n z o o m out" strategies suggests t h a t g r a d u a l z o o m i n g out  may  offer a n a d e q u a t e s u b s t i t u t e for t h e l a c k o f a n o v e r v i e w i n n a v i g a t i o n t a s k s s u c h as t h e o n e u s e d i n o u r s t u d y , w h e r e users m u s t follow a specific n a v i g a t i o n p a t h . W e h a d i n i t i a l l y b e l i e v e d t h a t t h e use o f t w o f o c u s areas i n t h i s s t u d y w o u l d e n a b l e users t o e x p l o r e m u l t i p l e a r e a s o f t h e s a m e d a t a s e t s i m u l t a n e o u s l y , a n d h e n c e p r o v i d e p e r f o r m a n c e benefits.  However, observation d a t a indicated that  this feature increased interface complexity, forcing subjects to invest m o r e cogn i t i v e effort  into c o o r d i n a t i n g n a v i g a t i o n between the m u l t i p l e focus  regions  t h a n they d i d into c o m p l e t i n g the task. A d d i t i o n a l l y , the presence of two focus a r e a s w a s p a r t l y r e s p o n s i b l e for t h e d e v e l o p m e n t o f i n t e r f a c e - s p e c i f i c i n p a r t i c u l a r the  strategies,  "overview" s t r a t e g y i n t h e P Z N - N o O V i n t e r f a c e , t h a t r e p r e -  s e n t e d a c o n f o u n d i n g f a c t o r . F i n a l l y , t h e H a l o - l i k e a r c s as i m p l e m e n t e d for t h i s s t u d y caused some subjects difficulties b y o c c l u d i n g regions of interest.  These  issues were a d d r e s s e d b y m e r g i n g t h e f o c u s areas i n e a c h i n t e r f a c e a n d m a k i n g t h e H a l o - l i k e a r c s t r a n s l u c e n t for t h e p u r p o s e s o f S t u d y 2. T h r e e o t h e r issues w i t h this s t u d y were n o t e d a n d a d d r e s s e d i n S t u d y 2. F i r s t , qualitative d a t a showed that m a n y subjects f o u n d it difficult to r e m e m b e r i n t e r m e d i a t e t a s k r e s u l t s , s u c h as t h e n u m b e r o f n o d e s o n t h e first p a t h exp l o r e d for a g i v e n t a s k i n s t a n c e .  S e c o n d , the absence of the experimenter in the  e x p e r i m e n t r o o m after t h e t r a i n i n g p e r i o d h a m p e r e d o u r a n a l y s i s o f i n t e r f a c e specific strategies.  S u b j e c t s i n S t u d y 2 were t h e r e f o r e g i v e n a p e n a n d p a p e r  to r e c o r d i n t e r m e d i a t e task results a n d observed t h r o u g h o u t the  experiment.  F i n a l l y , n a v i g a t i o n a n d reset a c t i o n d a t a f r o m t h i s s t u d y were n o t l o g g e d i n a f o r m a t c o n d u c i v e to s t a t i s t i c a l a n a l y s i s .  T h i s c a p a b i l i t y was  implemented in  S t u d y 2, a l l o w i n g t h e s e d a t a t o b e a n a l y z e d as a d d i t i o n a l d e p e n d e n t v a r i a b l e s .  49  Chapter 5  Study 2 T h e g o a l o f t h i s s t u d y w a s to e v a l u a t e t h e p e r f o r m a n c e o f p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n t e c h n i q u e s w i t h a n d w i t h o u t a n o v e r v i e w . S u b j e c t s u s e d i n t e r f a c e s b a s e d o n t h o s e u s e d i n S t u d y 1. e a c h p r o v i d i n g t h e best, p e r f o r m i n g l e v e l o f c o n t e x t as d i s c u s s e d i n C h a p t e r 4 . T h i s c h a p t e r d e s c r i b e s t h e s t u d y a n d p r e s e n t s t h e a s p e c t s o f its r e s u l t s r e l a t e d to t h e effects o f n a v i g a t i o n t e c h n i q u e .  5.1  Hypotheses  O u r h y p o t h e s e s for t h i s s t u d y w e r e m o t i v a t e d b y f i n d i n g s r e p o r t e d i n t h e l i t e r a t u r e a n d the r e s u l t s o f S t u d y 1. F i r s t , w e e x p e c t e d r u b b e r sheet n a v i g a t i o n t o p e r f o r i n b e t t e r t h a n p a n a n d z o o m n a v i g a t i o n b e c a u s e , as d i s c u s s e d i n C h a p t e r 2. f o c u s + c o n t e x t a p p r o a c h e s h a v e b e e n s h o w n to p e r f o r m b e t t e r t h a n p a n a n d  J z o o m interfaces  for a v a r i e t y o f n a v i g a t i o n t a s k s .  S e c o n d , we d i d n o t  expect  a n overview to significantly i m p r o v e the p e r f o r m a n c e of r u b b e r sheet n a v i g a t i o n , b e c a u s e f o c u s + c o n t e x t a p p r o a c h e s b y d e s i g n a t t e m p t to p r o v i d e t h e  same  c o n t e x t u a l i n f o r m a t i o n as a n o v e r v i e w , b u t in a n i n t e g r a t e d way.' F i n a l l y , expected  we  that an overview would significantly i m p r o v e the performance o f p a n  and z o o m navigation, because most previous studies have shown that  overviews  decrease n a v i g a t i o n t i m e a n d help the user m a i n t a i n o r i e n t a t i o n w i t h i n a p a n a n d z o o m interface. H3:  O u r h y p o t h e s e s were t h e r e f o r e as  follows:  R u b b e r sheet, n a v i g a t i o n will p e r f o r m b e t t e r t h a n p a n a n d z o o m n a v i g a tion, i n d e p e n d e n t l y of the presence or absence of a n overview.  H4:  F o r r u b b e r s h e e t n a v i g a t i o n , t h e p r e s e n c e o f a n o v e r v i e w will n o t r e s u l t i n  Chapter 5. Study 2  50  better performance.  H5:  F o r p a n a n d z o o m n a v i g a t i o n , the presence of a n overview will result in better performance.  5.2  Interfaces  T h e i n t e r f a c e s e x a m i n e d in t h i s s t u d y a r e i l l u s t r a t e d i n F i g u r e s 5.1 t o 5.4.  Each  o f t h e i n t e r f a c e s w a s b a s e d o n a n i n t e r f a c e u s e d i n S t u d y 1. as d e s c r i b e d i n d e t a i l in S e c t i o n 4.2.  B a s e d o n t h e r e s u l t s o f S t u d y 1. m u l t i p l e foci w e r e r e m o v e d f r o m  all interfaces, a n d H a l o - l i k e arcs in the P Z N interfaces were m a d e t r a n s l u c e n t , s u c h t h a t t h e y w e r e s t i l l v i s u a l l y s a l i e n t but, d i d n o t f u l l y o c c l u d e a r e a s o f the dataset.  T h e d e s i g n r a t i o n a l e for t h e s e c h a n g e s is d i s c u s s e d i n S e c t i o n  4.12.  T h e v a l u e s for level o f c o n t e x t a n d o v e r v i e w size i n e a c h i n t e r f a c e w e r e d e r i v e d f r o m t h e v a l u e s t h a t p r o v i d e d t h e b e s t p e r f o r m a n c e i n S t u d y 1, as o u t l i n e d in S e c t i o n 4.9.  In p a r t i c u l a r , in R S N interfaces, the fraction of the view o c c u p i e d  by the peripheral context fraction of the  a r e a w a s set  t o 50%. w h i l e i n P Z N i n t e r f a c e s ,  v i e w where H a l o - l i k e arcs c o u l d a p p e a r was  set  to 40%.  the In  i n t e r f a c e s w i t h o v e r v i e w s , o v e r v i e w s a n d d e t a i l v i e w s c o m p r i s e d 15% a n d 85% o f t h e t o t a l n u m b e r o f p i x e l s a v a i l a b l e , r e s p e c t i v e l y . T h e c a l c u l a t i o n o f levels o f c o n t e x t for t h i s s t u d y was s i m i l a r t o t h a t i n S t u d y 1. b u t r e f l e c t e d t h e use o f a s i n g l e focus i n e a c h i n t e r f a c e , as i l l u s t r a t e d i n F i g u r e s 5.5 a n d 5.6. 1. e a c h i n t e r f a c e a l w a y s p r o v i d e d a t o t a l  of 600.000 p i x e l s  A s in S t u d y  of i n f o r m a t i o n in all  views.  5.3  Task and Dataset  T h i s e x p e r i m e n t u t i l i z e d the s a m e t r e e t o p o l o g i c a l t a s k a n d d a t a s e t as S t u d y 1. B o t h t h e t a s k a n d t h e d a t a s e t a r e d e s c r i b e d in d e t a i l i n C h a p t e r 3.  Chapter 5. Study 2  F i g u r e 5.1:  RSN-NoOV  interface  u s e d i n S t u d y 2.  51  T h i s interface  s i n g l e f o c u s r a t h e r t h a n t w o f o c i as i n S t u d y 1 (see F i g u r e 4.1). w a s set t o  F i g u r e 5.2:  provided a  Level of context  50%.  P Z N - N o O V i n t e r f a c e u s e d i n S t u d y 2. T h i s i n t e r f a c e c o n s i s t e d o f a  s i n g l e f o c u s r a t h e r t h a n t w o f o c i as i n S t u d y  1 (see  F i g u r e 4.2),  t r a n s l u c e n t r a t h e r t h a n o p a q u e a r c s . L e v e l o f c o n t e x t w a s set t o  and provided 40%.  Chapter 5. Study 2  F i g u r e 5.4:  52  P Z N + O V i n t e r f a c e u s e d i n S t u d y 2. T h i s i n t e r f a c e p r o v i d e d a s i n g l e  f o c u s r a t h e r t h a n t w o f o c i as i n S t u d y 1 (see F i g u r e 4.4) a n d t r a n s l u c e n t t h a n o p a q u e a r c s . T h e o v e r v i e w c o m p r i s e d 15% o f t o t a l a v a i l a b l e  pixels.  rather  Chapter 5. Study 2  53  0  c c  c F  c  c c  F i g u r e 5.5: C a l c u l a t i o n o f l e v e l s o f c o n t e x t i n S t u d y 2 R S N i n t e r f a c e s .  Level of  n a v i g a t i o n a l c o n t e x t is t h e f r a c t i o n o f t h e s i z e o f t h e p e r i p h e r a l c o n t e x t C , to the t o t a l size of the d e t a i l view, f r a c t i o n of the size o f the o v e r v i e w ,  F+C.  O, t o  Level of overview context  the t o t a l size o f a l l v i e w s ,  areas, is  the  O+F+C.  0  c  1  ( F i g u r e 5.6:  F  C a l c u l a t i o n o f levels o f c o n t e x t  c  A  in S t u d y 2 P Z N interfaces.  The  d o t t e d l i n e i n d i c a t e s t h e b o u n d a r y b e t w e e n f o c u s a n d c o n t e x t r e g i o n s , w h i c h is not v i s u a l l y d e m a r c a t e d in the interfaces. c o n t e x t a r e as i n F i g u r e 5.5.  Levels of navigational a n d overview  Chapter 5. Study 2  5.4  54  Apparatus  T h e e x p e r i m e n t w a s c o n d u c t e d o n t h e two s y s t e m s u s e d t o c o n d u c t , S t u d y c o n f i g u r e d as d i s c u s s e d i n S e c t i o n  5.5  ].  4.4.  Participants  F o r t y s u b j e c t s (24 female) b e t w e e n 18 a n d 39 y e a r s o f age s u c c e s s f u l l y c o m p l e t e d t h e s t u d y a n d w e r e e a c h c o m p e n s a t e d $15 for t h e i r p a r t i c i p a t i o n . A l l s u b j e c t s were r i g h t - h a n d e d , h a d n o r m a l o r c o r r e c t e d t o n o r m a l v i s i o n , a n d w e r e n o t c o l o r blind.  P a r t i c i p a n t s were r e c r u i t e d t h r o u g h a d v e r t i s e m e n t s  posted  throughout  the u n i v e r s i t y c a m p u s a n d t h r o u g h an online p a r t i c i p a n t s c h e d u l i n g system. O r i g i n a l l y . 44 s u b j e c t s p a r t i c i p a t e d in the e x p e r i m e n t .  T w o of the  subjects  w e r e u n a b l e t o follow the t r a i n i n g i n s t r u c t i o n s s u c c e s s f u l l y , w h i l e t w o o t h e r s foll o w e d t h e i n s t r u c t i o n s b u t c o m m i t t e d four o r m o r e e r r o r s ( a n e r r o r r a t e g r e a t e r than  10%).  T h e s e subjects  were  t r e a t e d as o u t l i e r s for t h e p u r p o s e o f d a t a  a n a l y s i s , l e a v i n g a t o t a l o f 40 d a t a p o i n t s .  5.6  Design  T h e evaluation used a 2 (navigation, between subjects) by 2 (presence of overview between subjects)  by 7 ( b l o c k s , w i t h i n s u b j e c t s ) d e s i g n , w h e r e e a c h b l o c k c o n -  t a i n e d 5 t r i a l s . S u b j e c t s were r a n d o m l y a s s i g n e d t o e a c h of t h e f o u r c o m b i n a tions of n a v i g a t i o n a n d presence of overview. A s in S t u d y ), a between-subjects d e s i g n w a s c h o s e n for t h e n a v i g a t i o n a n d p r e s e n c e o f o v e r v i e w f a c t o r s to a v o i d p o t e n t i a l t r a n s f e r effects, as w e l l d u e to t h e t i m e r e q u i r e d t o t r a i n s u b j e c t s o n n a v i g a t i o n w i t h each t e c h n i q u e . D u e to the s i g n i f i c a n t l e a r n i n g effects f o u n d i n S t u d y 1. t h e n u m b e r o f b l o c k s w a s i n c r e a s e d f r o m 5 t o 7 to e n s u r e t h a t s u b j e c t p e r f o r m a n c e reached a p l a t e a u that w o u l d enable an a c c u r a t e c o m p a r i s o n of the effects o f n a v i g a t i o n a n d p r e s e n c e o f o v e r v i e w . P i l o t i n g s h o w e d t h a t 7 b l o c k s o f 5 t r i a l s e a c h w e r e sufficient for p e r f o r m a n c e to p l a t e a u .  Chapter 5. Study 2  5.7  55  Procedure  T h e e x p e r i m e n t was d e s i g n e d t o fit i n t o a s i n g l e 90 m i n u t e s e s s i o n .  T h e experi-  m e n t e r first i n s t r u c t e d s u b j e c t s o n t h e use o f t h e n a v i g a t i o n f u n c t i o n s a f f o r d e d b y t h e i n t e r f a c e to w h i c h t h e y h a d b e e n r a n d o m l y a s s i g n e d . S u b j e c t s were t h e n s h o w n t h e e x p e r i m e n t a l t a s k a n d i n s t r u c t e d t h a t t h e y were t o t a k e as m u c h t i m e as n e c e s s a r y to s o l v e it c o r r e c t l y w h i l e m a x i m i z i n g t h e i r efficiency.  T h e experi-  m e n t e r t h e n d e m o n s t r a t e d t h e t r a i n i n g s t r a t e g y to b e u s e d b y t h e s u b j e c t .  The  t r a i n i n g strategies varied d e p e n d i n g o n the navigation technique a n d presence o r a b s e n c e o f a n o v e r v i e w i n e a c h i n t e r f a c e , a n d c a n be f o u n d i n A p p e n d i x B . A l l t r a i n i n g strategies s t a r t e d w i t h d r a g g i n g out a l o n g t h i n selection along the h o r i z o n t a l p a t h between S e c t i o n 4.7.  two of the marked nodes,  area  as d e s c r i b e d i n  F o r t h e r u b b e r sheet i n t e r f a c e s , s e l e c t i n g a l o n g t h i n h o r i z o n t a l  area h a d t h e effect o f s t r e t c h i n g t h e d a t a s e t a l o n g the v e r t i c a l a x i s , as i l l u s t r a t e d in F i g u r e s 5.1 a n d 5.3.  F o r the p a n a n d z o o m interfaces, s e l e c t i n g a l o n g t h i n  h o r i z o n t a l area, h a d t h e effect o f z o o m i n g t h e c o n t e n t s o f t h e f o c u s b o x to fill t h e e n t i r e v i e w , as i l l u s t r a t e d i n F i g u r e s 5.2 a n d 5.4. F o r all interfaces, after z o o m i n g into the p a t h between  the marked  subjects were instructed to count nodes that became v i s u a l l y salient. ing  this step,  subjects  nodes, Follow-  were s h o w n how to d r a g out long t h i n horizontal a n d  v e r t i c a l s e l e c t i o n a r e a s to e x p a n d o t h e r c o m p r e s s e d r e g i o n s a l o n g t h e p a t h .  In  a c c o r d a n c e w i t h t h e r e s u l t s o f S t u d y 1, w h i c h s h o w e d t h a t u s i n g t h e p a n n i n g f u n c t i o n i m p r o v e d p e r f o r m a n c e , s u b j e c t s w e r e i n s t r u c t e d t o use p a n n i n g i n p a n and  z o o m i n t e r f a c e s , o r t h e e q u i v a l e n t o f p a n n i n g in r u b b e r sheet  t o m a k e a d j u s t m e n t s to t h e focus a r e a i f n e e d e d .  interfaces,  In i n t e r f a c e s w i t h o v e r v i e w s ,  s u b j e c t s w e r e i n s t r u c t e d h o w to use b o t h t h e o v e r v i e w a n d d e t a i l v i e w s for n a v igation a n d c o u n t i n g nodes,  b u t w e r e n o t e x p l i c i t l y t o l d t o n a v i g a t e in e i t h e r  view. F o r the P Z N - N o O V , a l t h o u g h the "overview" a n d "zoom i n . then z o o m out" strategies  p e r f o r m e d e q u a l l y well i n S t u d y 1. t h e  "overview" s t r a t e g y w a s  too  s i m i l a r to u s a g e p a t t e r n s in t h e P Z N + O V interface', a n d w a s e l i m i n a t e d as a  Chapter 5. Study 2  56  p o s s i b i l i t y t h r o u g h t h e r e m o v a l o f m u l t i p l e f o c i for t h i s s t u d y . t h e r e f o r e i n s t r u c t e d t o use t h e " z o o m i n . t h e n z o o m o u t  : :  Subjects  were  strategy. T h i s strategy  i n v o l v e d s l o w l y z o o m i n g o u t a n d a d d i n g n o d e s as t h e y a p p e a r e d a l o n g t h e p a t h u p t h e t r e e , as s h o w n i n F i g u r e 5.2. F o l l o w i n g the d i s c o v e r y of one of the w e r e i n s t r u c t e d to reset t h e  two  topological distances,  subjects  interface before d i s c o v e r i n g the second  distance.  T h i s s t r a t e g y w a s m o t i v a t e d b y the f i n d i n g s o f S t u d y 1 t h a t s h o w e d t h a t use o f reset b e t w e e n t h e d i s c o v e r y o f t h e  the  two topological distances i m p r o v e d  p e r f o r m a n c e . T h i s r e s u l t a n d its i m p l i c a t i o n s a r e d i s c u s s e d i n d e t a i l i n B o d n a r ' s thesis [12]. A f t e r b e i n g s h o w n the strategies,  subjects were given a t r a i n i n g block o f 5  t r i a l s . F o r e a c h o f t h e first 2 t r i a l s , t h e e x p e r i m e n t e r d e m o n s t r a t e d s o l v i n g t h e q u e s t i o n u s i n g t h e s t r a t e g i e s a n d t h e n a s k e d s u b j e c t s to r e p e a t t h i s s o l u t i o n . F o r t h e last 3 t r i a l s o f t h e s e s s i o n , s u b j e c t s p e r f o r m e d t h e t a s k o n t h e i r o w n , a n d t h e e x p e r i m e n t e r r e m i n d e d t h e m o f t h e t r a i n e d s t r a t e g y as n e e d e d . A t t h e e n d o f t h e t r a i n i n g session, subjects were given a one m i n u t e break before p r o c e e d i n g w i t h the e x p e r i m e n t .  D u r i n g b o t h the t r a i n i n g b l o c k a n d t h e e x p e r i m e n t ,  subjects  were p r o v i d e d w i t h a, p e n a n d p a p e r to r e c o r d i n t e r m e d i a t e t a s k r e s u l t s , a n d t h e experimenter r e m a i n e d in the experiment r o o m to observe their progress. T h e s e c h a n g e s f r o m S t u d y 1 w e r e i m p l e m e n t e d to a d d r e s s p r o c e d u r a l issues d i s c u s s e d in S e c t i o n  4.12.  In t h e e x p e r i m e n t , s u b j e c t s were p r e s e n t e d w i t h 7 b l o c k s , e a c h c o n t a i n i n g 5 t r i a l s , for a t o t a l o f 35 t r i a l s . A l l s u b j e c t s w e r e p r e s e n t e d w i t h a n i d e n t i c a l set o f questions.  T h e g r o u p i n g o f q u e s t i o n s to b l o c k w a s p r e d e t e r m i n e d , b u t t h e o r d e r  o f b l o c k s w a s r a n d o m l y g e n e r a t e d for e a c h s u b j e c t . T h e b l o c k s o f q u e s t i o n s w e r e v e r i f i e d to b e i s o m o r p h i c i n d i f f i c u l t y i n p i l o t i n g . T h e e x p e r i m e n t e r c o n t i n u e d to o b s e r v e t h e s u b j e c t t h r o u g h o u t the s t u d y , b u t n e v e r i n t e r v e n e d .  Subjects  were g i v e n a o n e m i n u t e b r e a k b e t w e e n e a c h b l o c k o f q u e s t i o n s . A t the e n d of the e x p e r i m e n t , subjects c o m p l e t e d questionnaires, w h i c h c a n b e f o u n d i n A p p e n d i x D . A s i n S t u d y 1, t h e q u e s t i o n n a i r e s w e r e u s e d t o c o l l e c t i n f o r m a t i o n a b o u t t h e s u b j e c t s ' d e m o g r a p h i c b a c k g r o u n d a n d c o m p u t e r u s a g e as  Chapter 5. Study 2  57  w e l l as r a t i n g s for ease o f u s e , e a s e o f n a v i g a t i o n , a n d i n t e r f a c e - s p e c i f i c on 5-point  L i k e r t scales.  F o r this study,  the questionnaires  features  also i n c l u d e d  the  N A S A - T L X scales [23], a s t a n d a r d i z e d i n s t r u m e n t for a s s e s s i n g v a r i o u s d i m e n sions o f w o r k l o a d . T h i s i n s t r u m e n t was i n c l u d e d to i m p r o v e o u r u n d e r s t a n d i n g o f h o w d e m a n d i n g each interface was p e r c e i v e d b y subjects.  Short informal in-  terviews were c o n d u c t e d w i t h some of the s u b j e c t s based o n their questionnaire responses.  5.8  Measures  O u r p e r f o r m a n c e measures were based o n logged d a t a a n d i n c l u d e d task c o m p l e tion times, errors, n a v i g a t i o n actions ( p a n , z o o m i n , a n d z o o m out), a n d reset actions. of S t u d y  T h e i n c l u s i o n o f t h e t w o l a t t e r m e a s u r e s w a s m o t i v a t e d b y the  results  1. w h e r e n a v i g a t i o n a n d reset p a t t e r n s w e r e f o u n d to h a v e a s t r o n g  influence on performance.  Self reported measures  were collected  p o s t - e x p e r i m e n t q u e s t i o n n a i r e , as d e s c r i b e d i n t h e p r e v i o u s s e c t i o n .  through  the  Like Study  1, t h i s s t u d y was d e s i g n e d t o m i n i m i z e e r r o r s , w i t h t a s k c o m p l e t i o n t i m e s a n d n u m b e r o f n a v i g a t i o n a n d r e s e t a c t i o n s u s e d as t h e p r i m a r y m e a s u r e s o f p e r f o r mance.  5.9  Results  T h i s section  presents the results  sures o f the experiment.  for b o t h p e r f o r m a n c e a n d s e l f - r e p o r t e d  mea-  T h e r e s u l t s for l e a r n i n g effects a n d n a v i g a t i o n t e c h n i q u e  a r e r e p o r t e d in d e t a i l , w h i l e t h e r e s u l t s for p r e s e n c e o f o v e r v i e w a r e s u m m a r i z e d . D e t a i l e d r e p o r t i n g o f t h e l a t t e r c a n be f o u n d i n B o d n a r s m a s t e r ' s thesis [12]. A  series o f A N O V A s  was  r u n to u n d e r s t a n d t h e effect  o v e r v i e w o n the p e r f o r m a n c e a n d self-reported measures.  of navigation  and  P r i o r to these a n a l y -  ses, o u t l i e r d a t a l y i n g m o r e t h a n 3 s t a n d a r d d e v i a t i o n s f r o m t h e m e a n s o f e a c h cell w e r e r e m o v e d f r o m t h e a n a l y s i s .  T h e Greenhouse-Geisser adjustment  used for n o n - s p h e r i c a l d a t a , a n d t h e B o n f e r r o n i a d j u s t m e n t  for p o s t - h o c  was com-  Chapter 5. Study 2  r>8  90 80  RSN-NoOV PZN-NoOV RSN+OV * - PZN+OV  20 10 0 2  3  4  5  6  7  Block  F i g u r e 5.7:  M e a n p e r - t r i a l c o m p l e t i o n t i m e s b y i n t e r f a c e for b l o c k s 1-7, i n sec-  onds (JV=40).  p a r i s o n s . A s i n t h e d i s c u s s i o n o f t h e r e s u l t s o f S t u d y 1 i n S e c t i o n 4.9, w e r e p o r t p a r t i a l e t a - s q u a r e d ( r / ) , a m e a s u r e o f effect size. T o i n t e r p r e t t h i s v a l u e , .01 is 2  a s m a l l effect size, .06 is m e d i u m , a n d .14 is l a r g e [17]. The  o v e r a l l r e s u l t s for m e a n c o m p l e t i o n t i m e s p e r t r i a l a r e i l l u s t r a t e d i n  F i g u r e 5.7. A s e x p e c t e d , p e r f o r m a n c e i m p r o v e d as s u b j e c t s p r o g r e s s e d t h r o u g h the e x p e r i m e n t , a l t h o u g h the rate of i m p r o v e m e n t d i d v a r y a m o n g the interfaces, w i t h a s i g n i f i c a n t m a i n effect o f b l o c k ( F ( 3 . 1 7 4 , 1 1 4 . 2 6 ) = 44.568, p < .001, r /  2  =  .553) a n d a s i g n i f i c a n t i n t e r a c t i o n b e t w e e n b l o c k a n d n a v i g a t i o n ( F ( 3 . 1 7 6 , 1 1 4 . 3 5 =  3 . 7 2 1 ) , p < 0.02, if  =  .094).  S e p a r a t e o n e - w a y r e p e a t e d m e a s u r e s A N O V A s were r u n for e a c h o f t h e i n t e r faces t o d e t e r m i n e p e r f o r m a n c e p l a t e a u s . P o s t - h o c p a i r w i s e c o m p a r i s o n s s h o w e d n o differences b e t w e e n  b l o c k s 5, 6, a n d 7 for a n y o f t h e i n t e r f a c e s , i n d i c a t i n g  that performance h a d reached a plateau b y the e n d of the experiment in all i n t e r f a c e s , a n d t h e r e f o r e t h a t t h e effect of b l o c k was s u c c e s s f u l l y c o n t r o l l e d for. T h u s , for t h e a n a l y s e s o f c o m p l e t i o n t i m e s , n a v i g a t i o n a c t i o n s , a n d reset a c t i o n s , w e f o c u s e x c l u s i v e l y o n b l o c k s 1 a n d 7, w h i c h r e p r e s e n t p e r f o r m a n c e a t  Chapter 5. Study 2  Dependent  variable  C o m p l e t i o n time (seconds) N u m b e r of navigation  actions  N u m b e r o f resets T a b l e 5.1:  59  Mean  Mean  F  Partial  (RSN)  (PZN)  59.58  47.49  13.744  .001  .276  4.55  4.04  3.087  .090  .079  1.228  0.968  4.912  .014  .156  Sig.  v  2  M e a n s a n d effects o f n a v i g a t i o n t e c h n i q u e for t h e c o m p l e t i o n  n u m b e r o f n a v i g a t i o n a c t i o n s , a n d n u m b e r o f resets d e p e n d e n t v a r i a b l e s D e g r e e s o f f r e e d o m a r e (1,36) for a l l d e p e n d e n t  the b e g i n n i n g a n d e n d o f the e x p e r i m e n t .  time,  (N=40).  variables.  F o r these a n a l y s e s , 2 ( n a v i g a t i o n )  by  2 ( p r e s e n c e o f o v e r v i e w ) b y 2 ( b l o c k ) A N O V A s were p e r f o r m e d . C o u n t e r to o u r h y p o t h e s i s H3,  b o t h o u r logged a n d self-reported  measures  showed t h a t p a n a n d z o o m n a v i g a t i o n o u t p e r f o r m e d r u b b e r sheet n a v i g a t i o n . T h e r e s u l t s for c o m p l e t i o n t i m e s b y n a v i g a t i o n for b l o c k s 1 a n d 7 a r e i l l u s t r a t e d in F i g u r e 5.8. and  B o t h at the b e g i n n i n g a n d at the end of the e x p e r i m e n t ,  pan  z o o m interfaces were significantly faster t h a n interfaces u s i n g r u b b e r sheet  navigation.  Subjects  a l s o p e r f o r m e d b o r d e r l i n e s i g n i f i c a n t l y fewer  navigation  a c t i o n s a n d s i g n i f i c a n t l y fewer resets u s i n g p a n a n d z o o m n a v i g a t i o n , as s h o w n in T a b l e 5.1. T w o - w a y ( n a v i g a t i o n b y o v e r v i e w ) A N O V A s were c o n d u c t e d o n e a c h o f t h e NASA-TLX  measures.. T h e s e analyses s h o w e d that m e n t a l d e m a n d was  i c a n t l y lower in the p a n a n d z o o m interfaces ( F ( ] , 3 6 ) = .105).  4.214, p <  S u b j e c t s also r e p o r t e d that p a n a n d z o o m interfaces were  easier t o n a v i g a t e ( F ( l , 3 6 )  =  10.385, p <  .005, » / = 2  r e p o r t e d measures s u p p o r t the results o b t a i n e d  signif-  .05, rf  =  significantly  . 2 2 4 ) . B o t h o f t h e s e self-  from the  logged  performance  o f o v e r v i e w h a d n o significant, effect, o n a n y o f t h e  performance  measures. Presence measures.  This  finding supports our hypothesis  hypothesis  H5.  T h e self-reported measures  H4,  but, is c o u n t e r  d i d , however,  favor a n  to  our  overview.  S u b j e c t s r e p o r t e d a l o w e r p h y s i c a l d e m a n d for i n t e r f a c e s w i t h a n o v e r v i e w a n d  F i g u r e 5.8: M e a n p e r - t r i a l c o m p l e t i o n t i m e s i n s e c o n d s b y n a v i g a t i o n t e c h n i q u e for b l o c k s 1 a n d 7, a b o v e , a n d b y b l o c k , b e l o w ( N = 4 0 ) .  P Z N was significantly  faster t h a n R S N i n b o t h b l o c k s , regardless o f p r e s e n c e o r a b s e n c e o f o v e r v i e w .  Chapter 5. Study 2 f o u n d t h e m m o r e e n j o y a b l e t o use.  61  B o d n a r s t h e s i s [12] r e p o r t s o n a n d d i s c u s s e d  these r e s u l t s i n m o r e d e t a i l . O n a v e r a g e , s u b j e c t s c o m m i t t e d 1.6 e r r o r s o v e r t h e c o u r s e o f t h e e x p e r i m e n t , for a m e a n e r r o r r a t e o f 4.7%.  T h e r e were no significant m a i n or interaction  effects o f n a v i g a t i o n o r p r e s e n c e o f o v e r v i e w o n e r r o r r a t e .  5.10  Summary of Results  W e s u m m a r i z e o u r r e s u l t s a c c o r d i n g to t h e h y p o t h e s e s s t a t e d i n S e c t i o n 5.1:  R3:  Pan and zoom  na.viga.tion interfaces p e r f o r m e d b e t t e r t h a n r u b b e r sheet  n a v i g a t i o n interfaces in terms of c o m p l e t i o n times, n u m b e r o f n a v i g a t i o n actions,  a n d n u m b e r o f reset, a c t i o n s .  as l o w e r i n p a n a n d z o o m  R4:  M e n t a l d e m a n d was also reported  interfaces.  F o r r u b b e r sheet n a v i g a t i o n , h a v i n g a n o v e r v i e w m a d e n o significant, difference i n t e r m s o f c o m p l e t i o n t i m e s , n a v i g a t i o n a c t i o n s , o r resets.  Having  a n o v e r v i e w was, however, r e p o r t e d to r e d u c e p h y s i c a l d e m a n d .  R5:  S i m i l a r l y , for p a n a n d z o o m n a v i g a t i o n , h a v i n g a n o v e r v i e w m a d e n o significant, d i f f e r e n c e i n t e r m s o f c o m p l e t i o n t i m e s , n a v i g a t i o n a c t i o n s , o r resets. H a v i n g an overview was, however, r e p o r t e d to reduce p h y s i c a l d e m a n d .  5.11  Discussion  In S t u d y 2. p a n a n d z o o m n a v i g a t i o n r e s u l t e d i n lower t a s k c o m p l e t i o n n u m b e r of n a v i g a t i o n actions, navigation.  time,  a n d n u m b e r o f reset a c t i o n s t h a n r u b b e r sheet  T h e s e results present convergent evidence  for p a n a n d z o o m  nav-  i g a t i o n o u t p e r f o r m i n g r u b b e r sheet, n a v i g a t i o n , a f i n d i n g t h a t c a n b e p a r t i a l l y e x p l a i n e d b y t h e n a t u r e o f t h e t a s k used in o u r s t u d y .  Following a topological  p a t h i n a l a r g e tree d a t a s e t u n d e r the d i s t o r t i o n i n h e r e n t i n r u b b e r sheet n a v i g a t i o n m a y h a v e c a u s e d a loss o f o r i e n t a t i o n . T h i s e x p l a n a t i o n is s u p p o r t e d b y the fact t h a t r u b b e r s h e e t i n t e r f a c e s  r e q u i r e d s i g n i f i c a n t l y m o r e reset  actions.  Chapter 5. Study 2 O u r observations  showed  that,  their l o c a t i o n in the d a t a s e t .  when they  62  subjects seemed disoriented in terms  of  frequently used the reset key to revert  to  t h e o r i g i n a l s t a t e o f t h e v i s u a l i z a t i o n , w h i c h i n d i c a t e s t h a t t h e n u m b e r o f reset a c t i o n s m a y b e a g o o d i n d i c a t o r o f loss o f o r i e n t a t i o n . T h e finding that pan a n d z o o m navigation performed better  than rubber  sheet n a v i g a t i o n is n o t c o n s i s t e n t w i t h G u t w i n a n d S k o p i k ' s f i n d i n g t h a t cus+context  interfaces  can  p e r f o r m as w e l l  t a s k s as p a n n i n g i n t e r f a c e s w i t h o v e r v i e w s  as o r b e t t e r  [22].  on  path  fo-  navigation  T o e x p l a i n t h i s d i s c r e p a n c y , it  m u s t b e n o t e d t h a t G u t w i n a n d S k o p i k ' s n o n - d i s t o r t i o n - b a s e d interfaces d i d n o t implement  z o o m i n g and featured an interaction m o d e l users found  F u r t h e r m o r e , t h e task  used  in their study  confusing.  r e q u i r e d users to move the  mouse  pointer a l o n g a p a t h . G u t w i n a n d S k o p i k suggested that a task that s i m p l y requires users to v i s u a l l y n a v i g a t e a p a t h , w h i c h was the case in o u r study, w o u l d be m u c h m o r e a m e n a b l e to interfaces w i t h o u t integrated focus a n d context. A l t h o u g h subjects c o u l d be expected to be m o r e f a m i l i a r w i t h p a n a n d z o o m n a v i g a t i o n f r o m previous experience, the difference in p e r f o r m a n c e between p a n a n d z o o m a n d r u b b e r s h e e t i n t e r f a c e s d i d n o t d e c r e a s e s i g n i f i c a n t l y as s u b j e c t s b e c a m e m o r e a d e p t i n t h e use o f t h e i n t e r f a c e s .  W e therefore speculate that  e x p e r i e n c e subjects g a i n e d w i t h r u b b e r sheet n a v i g a t i o n d u r i n g the m a y not  h a v e been  of n a v i g a t i o n . experience  sufficient  to o v e r c o m e  Further investigation  inherent difficulties  is r e q u i r e d t o d e t e r m i n e  the  experiment  w i t h this  form  whether  more  w i t h r u b b e r s h e e t n a v i g a t i o n c a n e n a b l e s u b j e c t s to i m p r o v e t h e i r  p e r f o r m a n c e b e y o n d the p l a t e a u o b s e r v e d in this study. In t e r m s o f s u b j e c t i v e e x p e r i e n c e , p a n a n d z o o m i n t e r f a c e s w e r e r a t e d b y s u b - , j e c t s as less m e n t a l l y d e m a n d i n g a n d e a s i e r t o n a v i g a t e t h a n t h e i r r u b b e r s h e e t equivalents, regardless of the presence of an overview.  T h i s r e s u l t is c o n s i s t e n t  w i t h r e s u l t s o f p r e v i o u s s t u d i e s [21. 25], w h i c h f o u n d t h a t n o n - d i s t o r t i o n p a n n i n g interfaces w i t h overviews were preferred to their d i s t o r t i o n - b a s e d c o u n t e r p a r t s . W e p o s t u l a t e that, since the p a n a n d z o o m interface w i t h o u t a n overview used in o u r s t u d y p r o v i d e d an a l t e r n a t i v e form of c o n t e x t u a l i n f o r m a t i o n (namely  Halo-  like a r c s ) , s u b j e c t s d i d n o t c o n s i d e r t h e l a c k o f a n o v e r v i e w to b e a l i a b i l i t y w h e n  Chapter 5. Study 2  63  a s s e s s i n g t h e i r p e r c e i v e d m e n t a l d e m a n d a n d ease o f n a v i g a t i o n . Q u a l i t a t i v e feedback  from questionnaires a n d interviews highlighted  three  m a i n areas w h e r e s u b j e c t s e n c o u n t e r e d d i f f i c u l t y w i t h r u b b e r sheet n a v i g a t i o n . F i r s t , s u b j e c t s r e p o r t e d t h a t t h e g l o b a l effect o f d i s t o r t i o n s r e s u l t i n g f r o m r u b b e r sheet n a v i g a t i o n p r e v e n t e d t h e m f r o m f o r m i n g a s t a b l e m e n t a l m o d e l o f t h e d a t a s e t , e v e n w h e n a n o v e r v i e w was p r e s e n t .  Second, subjects reported being  c o n f u s e d b y t h e effects o f the r u b b e r sheet n a v i g a t i o n e q u i v a l e n t o f p a n n i n g , w h i c h was also i m p l e m e n t e d u s i n g d i s t o r t i o n .  Some subjects stated that  they  w o u l d h a v e p r e f e r r e d t h i s o p e r a t i o n t o feel like p a n n i n g i n p a n a n d z o o m i n terfaces t h e y h a v e p r e v i o u s l y e x p e r i e n c e d , s u c h as G o o g l e M a p s [20].  Finally,  a n u m b e r o f s u b j e c t s i d e n t i f i e d t h e use o f a s i n g l e fixed focus r e g i o n i n r u b b e r sheet n a v i g a t i o n i n t e r f a c e s as a h i n d r a n c e , a n d s u g g e s t e d t h a t t h e y w o u l d h a v e benefitted  f r o m m o v a b l e , r e s i z a b l e f o c u s a r e a s , as i m p l e m e n t e d i n t h e o r i g i n a l  T r e e J u x t a p o s e r a p p l i c a t i o n [37].  These  findings  suggest that the  constraints  i m p o s e d o n t h e size a n d l o c a t i o n o f f o c u s areas in o u r s t u d i e s a d v e r s e l y t h e u s a b i l i t y o f t h e r u b b e r sheet n a v i g a t i o n interfaces.  affected  O u r original rationale  for i m p o s i n g t h e s e c o n s t r a i n t s was t o c o n t r o l t h e level o f c o n t e x t , a p a r a m e t e r t h a t w a s s h o w n t o h a v e n o s i g n i f i c a n t effect o n p e r f o r m a n c e i n S t u d y 1.  For  t h i s r e a s o n , we r e c o m m e n d t h a t f u t u r e s t u d i e s o f r u b b e r s h e e t n a v i g a t i o n r e l a x t h e s e c o n s t r a i n t s as n e c e s s a r y navigation A  to p r o v i d e usability o n a p a r w i t h c o m p a r i s o n  techniques.  p o s s i b l e c o n f o u n d i n g f a c t o r i n t h i s s t u d y was t h e l a c k o f a d j u s t m e n t  t h e b e s t - p e r f o r m i n g levels o f c o n t e x t d e r i v e d f r o m S t u d y 1 r e s u l t s t o  to  account  for t h e m e r g i n g o f t h e t w o focus r e g i o n s u s e d i n t h a t s t u d y i n t o a s i n g l e  focus  r e g i o n . H o w e v e r , we p o s t u l a t e t h a t t h e m a g n i t u d e o f s u c h a n a d j u s t m e n t w o u l d h a v e b e e n m i n o r , a n d its i m p a c t n e g l i g i b l e g i v e n t h e l a c k o f s i g n i f i c a n t effect o f l e v e l o f c o n t e x t o n t h e r e s u l t s o f S t u d y 1.  64  Chapter 6  Conclusions and Future Work T h i s t h e s i s p r e s e n t e d t h e first e m p i r i c a l e v a l u a t i o n s i n t h e i n f o r m a t i o n v i s u a l i z a tion l i t e r a t u r e c o m p a r i n g p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n techniques. We  c o n d u c t e d two e x p e r i m e n t s , each o f w h i c h involved interfaces  implement-  i n g J i l l c o m b i n a t i o n s o f t h e s e two n a v i g a t i o n t e c h n i q u e s w i t h a n d w i t h o u t , a n overview.  O u r results indicate that p a n a n d z o o m n a v i g a t i o n was  significantly  faster t h a n r u b b e r s h e e t n a v i g a t i o n , r e q u i r e d fewer n a v i g a t i o n a c t i o n s , a n d dem a n d e d less m e n t a l effort to c o m p l e t e a t o p o l o g i c a l c o m p a r i s o n t a s k i n a l a r g e t r e e d a t a s e t . r e g a r d l e s s o f t h e p r e s e n c e o f a n o v e r v i e w . W e a l s o f o u n d t h a t level of context  did not  significantly influence  performance with either  navigation  technique, while interface-specific strategies developed b y subjects d i d . A s c o n t r o l l e d l a b o r a t o r y e x p e r i m e n t s , the studies d e s c r i b e d in this thesis are n e c e s s a r i l y l i m i t e d i n t e r m s o f r e a l i s m a n d g e n e r a l i z a b i l i t y [36].  T h e derivation  of the task e m p l o y e d in the s t u d y f r o m discussions w i t h experts in the d o m a i n of p h y l o g e n e t i c b i o l o g y , c o m b i n e d w i t h t h e use o f a d a t a s e t f r o m t h e s a m e d o m a i n , render this work m o r e ecologically  valid  than most  of the studies that  have  p r e c e d e d it i n t h e l i t e r a t u r e . H o w e v e r , t h e d e g r e e o f r e a l i s m p r o v i d e d b y t h e s e f a c t o r s is t e m p e r e d b y t h e use o f n o n - e x p e r t s u b j e c t s  a n d a task that  require a knowledge o f phylogenetic biology. T h e g e n e r a l i z a b i l i t y of the  d i d not results  of t h i s s t u d y is l i k e w i s e l i m i t e d b y t h e use o f a s i n g l e , a l b e i t c o m p o u n d , t a s k to r e p r e s e n t t h e v a r i e t y o f p o s s i b l e t o p o l o g i c a l t a s k s o f i n t e r e s t t o  phylogenetic  b i o l o g i s t s , as well as t h e u s a b i l i t y issues w i t h o u r i m p l e m e n t a t i o n o f r u b b e r sheet  Chapter 6. Conclusions and Future Work navigation identified in the previous section.  65  G i v e n these l i m i t a t i o n s , this w o r k  s h o u l d b e r e g a r d e d as a s t a r t i n g p o i n t for f u r t h e r e x p l o r a t i o n i n t o t h e p r o p e r t i e s o f p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n r a t h e r t h a n a d e f i n i t i v e s t a t e m e n t about their relative performance. S e v e r a l p o s s i b i l i t i e s for f u t u r e s t u d i e s a r i s e f r o m t h e r e s u l t s d e s c r i b e d i n t h i s thesis.  C o m p a r i s o n s of p a n a n d z o o m a n d r u b b e r sheet n a v i g a t i o n  methods  u s i n g o t h e r t o p o l o g i c a l t a s k s s u c h as t h o s e d e s c r i b e d i n C h a p t e r 3, as well  as  m o r e g e n e r a l n o n - t o p o l o g i c a l t a s k s a n d different t y p e s o f d a t a s e t s , c o u l d y i e l d a n i m p r o v e d u n d e r s t a n d i n g of the relative strengths  a n d weaknesses of  each  n a v i g a t i o n t e c h n i q u e . F o r i n s t a n c e , a f u t u r e e x p e r i m e n t c o u l d use a s t e e r i n g t a s k s i m i l a r t o t h a t u s e d b y G u t w i n a n d S k o p i k [22] t o d e t e r m i n e w h e t h e r t h e b e n e f i t s o f t h e i n t e g r a t i o n o f f o c u s a n d c o n t e x t r e g i o n s p r o v i d e d b y t h e fisheye v i e w s i n t h a t s t u d y e x t e n d t o r u b b e r sheet n a v i g a t i o n . extended  T h e c o m p a r i s o n c o u l d also b e  to i n c l u d e o t h e r v a r i a n t s o n t h e p a n a n d z o o m a n d  focus+context  n a v i g a t i o n m e t a p h o r s , s u c h as fisheye v i e w s a n d s e m a n t i c z o o m i n g . The  findings  f r o m S t u d y 1 suggest that n a v i g a t i o n strategy c a n have a sig-  n i f i c a n t i m p a c t o n user p e r f o r m a n c e , as w e l l as t h e p o s s i b i l i t y o f a n i n t e r a c t i o n b e t w e e n s t r a t e g i e s d e v e l o p e d b y users a n d a f f o r d a n c e s p r o v i d e d b y n a v i g a t i o n techniques.  T h e r e f o r e , another obvious next step w o u l d be to c o n d u c t a system-  atic e x p l o r a t i o n of the strategies users n a t u r a l l y a d o p t o n their o w n t o  complete  different t a s k s w i t h e a c h t y p e o f n a v i g a t i o n e x a m i n e d i n o u r s t u d y .  It w o u l d  b e e q u a l l y v a l u a b l e t o e x a m i n e p o s s i b i l i t i e s for h o w t h e n a v i g a t i o n  techniques  e x a m i n e d i n t h i s s t u d y m i g h t b e t u n e d t o b e t t e r a c c o m m o d a t e s t r a t e g i e s users w o u l d n a t u r a l l y t e n d to develop w h e n using t h e m . F o r instance, future studies c o u l d e x a m i n e w h e t h e r , as s u g g e s t e d b y o u r  findings,  users c a n d e v e l o p z o o m i n g  s t r a t e g i e s t h a t p r o v i d e p e r f o r m a n c e b e n e f i t s e q u i v a l e n t to t h o s e o f a n o v e r v i e w , a n d d e t e r m i n e w h e t h e r z o o m i n g e n h a n c e m e n t s s u c h as s p e e d - d e p e n d e n t  auto-  m a t i c z o o m i n g [26] c a n f u r t h e r i m p r o v e p e r f o r m a n c e w i t h s u c h s t r a t e g i e s . T h e n e e d for m o r e t h a n o n e f o c u s r e g i o n is a n o t h e r issue t h a t affected  the  r e s u l t s o f t h e s t u d i e s d e s c r i b e d i n t h i s thesis a n d d e s e r v e s f u r t h e r i n v e s t i g a t i o n . O u r S t u d y 1 s h o w e d t h a t t h e p r e s e n c e o f t w o f o c u s areas i n t h e o r i g i n a l v e r s i o n s  Chapter 6. Conclusions and Future Work  66  o f o u r i n t e r f a c e s i n c r e a s e d t h e i r c o m p l e x i t y a n d r e q u i r e d s u b j e c t s t o invest m u c h c o g n i t i v e effort i n t o c o o r d i n a t i n g n a v i g a t i o n b e t w e e n t h e m .  too  However, a  n u m b e r o f s u b j e c t s i n S t u d y 2 s u g g e s t e d t h a t m u l t i p l e f o c u s areas w o u l d h a v e p r o v e d b e n e f i c i a l , e s p e c i a l l y i n c o n j u n c t i o n w i t h r u b b e r sheet n a v i g a t i o n .  An  e m p i r i c a l e x a m i n a t i o n of the c o m b i n a t i o n s of n a v i g a t i o n techniques, tasks, a n d d a t a s e t s for w h i c h m u l t i p l e f o c u s areas m a y p r o v e e i t h e r h e l p f u l o r a h i n d r a n c e could provide a valuable addition to the information visualization literature. F i n a l l y , a l o g i c a l d i r e c t i o n for c o n t i n u i n g t h i s w o r k is to e x p l o r e h o w  the  n a v i g a t i o n m e t h o d s e x a m i n e d i n it c o m p a r e w h e n used b y d o m a i n experts in phylogenetic biology in their work. A s previously mentioned, although subjects in our study became  m o r e p r o f i c i e n t i n t h e i r use o f r u b b e r sheet  navigation  o v e r t h e c o u r s e o f t h e e x p e r i m e n t , a n d t h e i r l e a r n i n g o c c u r r e d a t a faster  rate  t h a n t h a t of subjects u s i n g p a n a n d z o o m n a v i g a t i o n , this i m p r o v e m e n t was not sufficient  to significantly decrease the p e r f o r m a n c e differential between t h e m .  It w o u l d t h e r e f o r e b e v a l u a b l e t o i n v e s t i g a t e w h e t h e r t h e use o f r u b b e r sheet n a v i g a t i o n b y d o m a i n e x p e r t users o v e r a n e x t e n d e d p e r i o d o f t i m e w o u l d r e s u l t i n t h i s g a p d e c r e a s i n g t o t h e p o i n t w h e r e p e r f o r m a n c e w i t h r u b b e r sheet n a v i g a t i o n is n o t s i g n i f i c a n t l y different f r o m t h a t w i t h p a n a n d z o o m n a v i g a t i o n . S u c h a n i n v e s t i g a t i o n c o u l d also b e e x t e n d e d  into other aspects of p o t e n t i a l future  w o r k we h a v e d i s c u s s e d here, s u c h as t a s k - s p e c i f i c s t r a t e g i e s a n d m u l t i p l e f o c u s a r e a s , t o d e t e r m i n e h o w t h e u s a g e p a t t e r n s o f d o m a i n e x p e r t s differ f r o m t h o s e of non-expert  users.  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In  abstracts of the SIGCHI  CHI '03: Extended  conference on Human factors in computing systems.  pages 838-839; N e w Y o r k , N Y , U S A . A C M Press.  Appendix A  Study 1 Training Protocol  Appendix A. Study 1 Training Protocol  75  A l l interfaces T h a n k y o u for y o u r w i l l i n g n e s s t o p a r t i c i p a t e i n o u r e x p e r i m e n t .  Y o u will  h e l p i n g u s e v a l u a t e d i f f e r e n t t e c h n i q u e s for v i s u a l i z i n g l a r g e d a t a s e t s .  be  Y o u will  be a s k e d to c o m p l e t e a series o f t a s k s t h a t i n v o l v e d e t e r m i n i n g r e l a t i v e d i s t a n c e s in l a r g e t r e e s .  F i r s t , let's r e v i e w s o m e c o n c e p t s t h a t w i l l h e l p y o u to c o m p l e t e  the tasks.  Present subjects with paper tests. The  task y o u will p e r f o r m  topological distance between  in this e x p e r i m e n t consists o f d e t e r m i n i n g the a series o f m a r k e d n o d e s  in the d i s p l a y e d tree,  where t o p o l o g i c a l distances are m e a s u r e d b y the n u m b e r o f b l a c k squares between m a r k e d n o d e s .  R e m e m b e r from the tests that y o u just c o m p l e t e d  that  topological distance will not equal geometric distance. We  w i l l n o w e x p l o r e t h e features o f t h e i n t e r f a c e y o u w i l l  use.  RSN-NoOV T h i s i n t e r f a c e e n a b l e s y o u t o e x p l o r e t h e d a t a s e t u s i n g a series o f z o o m i n g a n d p a n n i n g a c t i o n s t h a t use  t h e m e t a p h o r o f s t r e t c h i n g a r u b b e r sheet w i t h  its  borders tacked down. The  left m o u s e b u t t o n w i l l a l l o w y o u t o d r a g o u t a b o x . t h e c o n t e n t s o f w h i c h  w i l l fill o n e o f t h e R E D o r O R A N G E focus b o x e s . T h e rest o f t h e t r e e w i l l t h e n be s q u i s h e d a r o u n d t h e f o c u s b o x b u t w i l l r e m a i n v i s i b l e at a l l t i m e s .  Ask participant  to try dragging out a box  A s y o u are d r a g g i n g o u t a box. y o u m a y h o l d d o w n the S H I F T key to i n d i c a t e t h a t y o u w o u l d like t h i s b o x t o be the n e w R E D focus b o x , o r h o l d d o w n t h e CTRL  k e y to i n d i c a t e t h a t y o u w o u l d like t h i s b o x to b e t h e n e w  focus b o x . N o t e a l s o t h a t t h e S H I F T k e y is a b o v e t h e C T R L RED  f o c u s b o x is a b o v e t h e O R A N G E  Ask participant  O R A N G E  key. just like t h e  focus b o x .  to try dragging out a box using SHIFT  If y o u d o n o t s e l e c t e i t h e r the S H I F T  or C T R L  and.  CTRL  key, t h e t o o l w i l l  choose  w h i c h focus b o x to place the contents of y o u r new box based o n the p r o x i m a t e l y  Appendix A. Study 1 Training Protocol  of y o u r n e w l y d r a g g e d o u t b o x t o t h e e x i s t i n g R E D a n d O R A N G E You  76  focus  boxes.  c a n z o o m o u t b y d r a g g i n g o u t a b o x w h i c h is l a r g e r t h a n e i t h e r o f  colored focus  boxes.  Ask participant The  the  to try zooming out  r i g h t m o u s e b u t t o n w i l l a l l o w y o u to p a n h o r i z o n t a l l y a n d v e r t i c a l l y  within the dataset using either a h o r i z o n t a l or vertical d r a g m o t i o n s , which will let y o u fine t u n e y o u r s e l e c t i o n .  Ask participant  to try panning  PZN-NoOV T h i s interface enables y o u to explore the d a t a s e t using two v i e w s w h i c h y o u c a n n a v i g a t e t h r o u g h a series o f p a n a n d z o o m  Show subject paper illustration The  actions.  of two views  t w o d e t a i l v i e w s a r e i n d e p e n d e n t o f o n e a n o t h e r , so y o u c a n  in o n e w i t h o u t a f f e c t i n g t h e o t h e r .  navigate  It is a l s o p o s s i b l e t o o v e r l a p t h e t w o d e t a i l  v i e w s , a n d e v e n h a v e o n e i n s i d e t h e o t h e r . T h e left m o u s e b u t t o n w i l l a l l o w y o u to d r a g o u t a b o x w h i c h w i l l b e c o m e t h e n e w e x t e n t o f y o u r d e t a i l v i e w .  Ask participant  to try zooming in  O n c e y o u a r e z o o m e d i n , y o u m a y h o l d d o w n the right, m o u s e b u t t o n a n d pan  in a n y d i r e c t i o n . Y o u c a n n o t p a n if y o u are z o o m e d out entirely. .447c  participant  to try panning  H o l d i n g d o w n the m i d d l e mouse b u t t o n a n d dragging the mouse toward y o u will a l l o w y o u to z o o m o u t .  A s y o u z o o m o u t . y o u m a y also d r a g the  mouse  in t h e o p p o s i t e d i r e c t i o n t o z o o m b a c k i n . b u t o n l y to t h e e x t e n t t h a t y o u  first  b e g a n to z o o m o u t .  Ask participant  to try zooming out  If a m a r k e d n o d e is n o t c u r r e n t l y in v i e w , a n a r c w i l l a p p e a r at the b o r d e r of the d e t a i l v i e w , i n d i c a t i n g t h e d i r e c t i o n a n d d i s t a n c e f r o m y o u r c u r r e n t f o c u s b o x to t h e m a r k e d n o d e . T h e a r c is p a r t o f a c i r c u l a r r i n g t h a t s u r r o u n d s o n e o f the n o d e s w h i c h is c u r r e n t l y o f f - s c r e e n .  T h i s r i n g is just, l a r g e e n o u g h t o r e a c h  Appendix A. Study 1 Training Protocol  77  the b o r d e r region o f the display. T h e c o l o u r of the a r c indicates the c o l o u r o f t h e m a r k e d n o d e it r e p r e s e n t s .  O n c e a m a r k e d n o d e is v i s i b l e o n s c r e e n ,  the  a r c w i l l d i s a p p e a r . N o m a r k s w i l l a p p e a r i n the o v e r v i e w w i n d o w s i n c e m a r k e d n o d e s are always visible. A r c s are view  dependent.  RSN+OV T h i s interface enables y o u to explore the dataset u s i n g a series of z o o m i n g a n d p a n n i n g a c t i o n s t h a t use t h e m e t a p h o r o f s t r e t c h i n g a r u b b e r sheet w i t h  its  b o r d e r s tacked clown. A separate w i n d o w will p r o v i d e y o u w i t h an o v e r v i e w of the dataset. a n d will not be d i s t o r t e d . The  left m o u s e b u t t o n w i l l a l l o w y o u t o d r a g o u t a b o x , t h e c o n t e n t s o f w h i c h  w i l l fill o n e o f t h e R E D o r O R A N G E  f o c u s b o x e s . T h e r e s t o f t h e tree w i l l t h e n  be s q u i s h e d a r o u n d the focus box b u t will r e m a i n visible at all times.  Ask participant  to try dragging out a box  A s y o u a r e d r a g g i n g o u t a. b o x . y o u m a y h o l d d o w n t h e S H I F T k e y to i n d i c a t e t h a t y o u w o u l d like t h i s b o x t o b e t h e n e w R E D f o c u s b o x . o r h o l d d o w n CTRL  k e y t o i n d i c a t e t h a t y o u w o u l d like t h i s b o x t o b e t h e n e w  the  ORANGE  f o c u s b o x . N o t e a l s o that, t h e S H I F T k e y is a b o v e t h e C T R L key, j u s t like t h e RED  f o c u s b o x is a b o v e t h e O R A N G E  Ask participant  focus box.  to try dragging out a box using SHIFT  If y o u d o n o t select e i t h e r t h e S H I F T  or C T R L  and  CTRL  key, t h e t o o l w i l l  choose  w h i c h focus box to p l a c e the contents of y o u r new b o x b a s e d o n the p r o x i m a t e l y of y o u r newly d r a g g e d out box to the existing R E D a n d O R A N G E You  focus  boxes.  c a n z o o m o u t b y d r a g g i n g o u t a b o x w h i c h is l a r g e r t h a n e i t h e r o f  c o l o r e d focus  boxes.  Ask participant The  the  to try zooming out  r i g h t m o u s e b u t t o n w i l l a l l o w y o u to p a n h o r i z o n t a l l y a n d v e r t i c a l l y  w i t h i n the dataset u s i n g either a h o r i z o n t a l or vertical d r a g motions, w h i c h will let. y o u fine t u n e y o u r s e l e c t i o n .  Ask participant  to try panning  Appendix A. Study 1 Training Protocol  78  A separate smaller w i n d o w will p r o v i d e y o u with an overview of the  dataset.  a n d i n d i c a t e w h e r e in t h e d a t a s e t y o u r c u r r e n t f o c u s b o x e s a r e . I n t h e o v e r v i e w , t h e left m o u s e b u t t o n w i l l a l l o w y o u t o d r a g o u t a b o x , t h e c o n t e n t s o f w h i c h w i l l fill o n e o f t h e R E D o r O R A N G E  focus boxes.  A s y o u are d r a g g i n g out  a  b o x : y o u m a y h o l d d o w n t h e S H I F T k e y t o i n d i c a t e t h a t y o u w o u l d like t h i s box to be the new R E D focus b o x , or h o l d d o w n the C T R L key to indicate t h a t y o u w o u l d l i k e t h i s b o x to be t h e n e w O R A N G E  Ask participant  to try dragging  focus b o x .  out a box in the overview  using  SHIFT  and  CTRL You  m a y also hold d o w n  the right mouse  b u t t o n while inside one of  the  b o x e s r e p r e s e n t i n g t h e l o c a t i o n o f y o u r f o c u s b o x a n d m o v e it t o w h e r e v e r y o u like w i t h i n t h e b o u n d s o f t h e o v e r v i e w u s i n g a series o f d r a g a c t i o n s .  Ask participant  to try panning  in the  overview  PZN+OV  '  T h i s i n t e r f a c e e n a b l e s y o u to e x p l o r e t h e d a t a s e t u s i n g t w o d e t a i l v i e w s w h i c h y o u c a n n a v i g a t e t h r o u g h a series o f p a n a n d z o o m a c t i o n s .  Show The  subject, paper illustration  of two views  t w o d e t a i l v i e w s a r e i n d e p e n d e n t o f o n e a n o t h e r , so y o u c a n  in o n e w i t h o u t a f f e c t i n g t h e o t h e r .  navigate  It is a l s o p o s s i b l e to o v e r l a p t h e t w o d e t a i l  v i e w s , a n d e v e n h a v e o n e i n s i d e t h e o t h e r . T h e left m o u s e b u t t o n w i l l a l l o w y o u to d r a g o u t a b o x w h i c h will b e c o m e the new extent of y o u r d e t a i l view.  Ask participant  to try zooming  in a detail  view  O n c e y o u are z o o m e d i n . y o u m a y h o l d d o w n the right m o u s e b u t t o n a n d p a n i n a n y d i r e c t i o n . Y o u c a n n o t p a n if y o u a r e z o o m e d o u t e n t i r e l y .  Ask participant  to try panning  in a detail  view  H o l d i n g d o w n the m i d d l e m o u s e b u t t o n a n d d r a g g i n g the m o u s e t o w a r d y o u will allow y o u to z o o m out.  A s y o u z o o m o u t , y o u m a y a l s o d r a g the  mouse  in the o p p o s i t e d i r e c t i o n t o z o o m b a c k i n , b u t o n l y to t h e e x t e n t t h a t y o u first began to z o o m out.  Appendix Ask participant  A. Study 1 Training  Protocol  79  to try zooming out in a detail view  A separate smaller window will p r o v i d e y o u w i t h a n overview of the dataset. and  i n d i c a t e w h e r e i n the d a t a s e t y o u r c u r r e n t d e t a i l v i e w s a r e . I n t h e  overview,  t h e left m o u s e b u t t o n w i l l allow- y o u to d r a g o u t a b o x w h i c h w i l l b e c o m e new extent of y o u r detail view. d o w n the S H I F T RED  A s y o u are d r a g g i n g out a box. y o u m a y h o l d  key to i n d i c a t e t h a t y o u w o u l d  detail view, or hold d o w n the C T R L  this box to be the new O R A N G E d e t a i l  Ask participant  the  like t h i s b o x  to be the  new  k e y t o i n d i c a t e t h a t y o u w o u l d like  view.  to try zooming in, overview using SHIFT  N o t e a l s o t h a t t h e S H I F T k e y is a b o v e t h e C T R L detail view a b o v e the O R A N G E d e t a i l view.  and  key. j u s t  CTRL like the R E D  Y o u m a y also h o l d d o w n the right  m o u s e b u t t o n w h i l e inside o n e o f t h e b o x e s r e p r e s e n t i n g  the l o c a t i o n of y o u r  d e t a i l v i e w a n d m o v e it to w h e r e v e r y o u like w i t h i n the b o u n d s o f t h e  overview  u s i n g a series o f d r a g a c t i o n s .  overview  T h e modifier keys only w o r k in the  window.  Ask participant  to try panning in overview using SHIFT  and  CTRL  If a m a r k e d n o d e is n o t c u r r e n t l y i n v i e w , a n a r c w i l l a p p e a r a t t h e b o r d e r of t h e d e t a i l v i e w , i n d i c a t i n g t h e d i r e c t i o n a n d d i s t a n c e f r o m y o u r c u r r e n t focus b o x to t h e m a r k e d n o d e . T h e a r c is p a r t o f a c i r c u l a r r i n g t h a t s u r r o u n d s o n e o f t h e n o d e s w h i c h is c u r r e n t l y o f f - s c r e e n . the b o r d e r region of the display. the m a r k e d node arc  it r e p r e s e n t s .  T h i s r i n g is j u s t l a r g e e n o u g h t o r e a c h  T h e colour of the arc indicates O n c e a'marked node  the colour of  is v i s i b l e o n s c r e e n ,  the  w i l l d i s a p p e a r . N o m a r k s w i l l a p p e a r in t h e o v e r v i e w w i n d o w s i n c e m a r k e d  nodes are always visible.  A r c s are view  dependent.  A l l interfaces Do  y o u have any questions a b o u t this The  R key c a n be pressed  interface?  to reset y o u r c u r r e n t v i e w t o its i n i t i a l s t a r t u p  state. The  E S C key c a n b e p r e s s e d d u r i n g a b o x d r a g a c t i o n to c a n c e l y o u r c u r r e n t  Appendix A. Study 1 Training Protocol  80  drag. A question p a n e l at the top o f the screen will d i s p l a y a question w h i c h will r e q u i r e y o u to use t h e i n t e r f a c e t o s o l v e . T h e q u e s t i o n w i l l a s k y o u t o c o m p a r e the topological distances between distance between  m a r k e d n o d e s i n t h e tree.  m a r k e d nodes will never be equal.  T h e topological  T h e question will  never  c h a n g e , b u t t h e l o c a t i o n o f t h e m a r k e d n o d e s w i l l , t h u s y o u w i l l b e r e q u i r e d to n a v i g a t e a n d e x p l o r e different a r e a s w i t h i n t h e l a r g e t r e e to a n s w e r t h e q u e s t i o n correctly. W h e n y o u h a v e d i s c o v e r e d t h e a n s w e r , w e a s k t h a t y o u select t h e a p p r o p r i a t e check b o x a n d click o n the s u b m i t b u t t o n . T h i s will allow y o u to m o v e o n t o the next question.  A n i n s t r u c t i o n p a n e l a t t h e left o f t h e i n t e r f a c e w i l l s e r v e as a  r e m i n d e r of interface specific c o n t r o l s W e will now ask y o u to c o m p l e t e a series of t r a i n i n g tasks u s i n g this interface. T h e r e is n o t i m e l i m i t for c o m p l e t i n g t h e s e t a s k s - we w a n t y o u t o t a k e as m u c h t i m e as y o u n e e d t o e n s u r e t h a t y o u r a n s w e r is c o r r e c t . W e w a n t to e m p h a s i z e t h a t we a r e e v a l u a t i n g t h e s y s t e m a n d n o t y o u r a b i l i t y t o use it. F o r t h i s r e a s o n , y o u w i l l r e c e i v e n o f e e d b a c k as t o w h e t h e r y o u r a n s w e r s for t h e t a s k s w e r e c o r r e c t . A boxes.  good strategy  for s o l v i n g t h e  t a s k s is to d r a w o u t l o n g h o r i z o n t a l t h i n  T h i s w i l l h e l p y o u to see t h e l a r g e r tree in m o r e d e t a i l .  Appendix B  Study 2 Training Protocol  Appendix B. Study 2 Tiaining Protocol All  82  interfaces  T h a n k y o u for y o u r w i l l i n g n e s s t o p a r t i c i p a t e i n o u r e x p e r i m e n t .  Y o u will  be  h e l p i n g us e v a l u a t e different t e c h n i q u e s for v i s u a l i z i n g l a r g e d a t a s e t s . Y o u w i l l b e a s k e d t o c o m p l e t e a series o f t a s k s t h a t i n v o l v e d e t e r m i n i n g r e l a t i v e d i s t a n c e s in l a r g e t r e e s . F i r s t , let's r e v i e w s o m e c o n c e p t s t h a t w i l l h e l p y o u to the  complete  tasks.  Present subjects with paper tests. The  task y o u will p e r f o r m in this e x p e r i m e n t consists o f d e t e r m i n i n g the  t o p o l o g i c a l d i s t a n c e between a series of m a r k e d nodes in the where topological distances tween m a r k e d nodes.  tree,  are m e a s u r e d by the n u m b e r o f b l a c k squares be-  R e m e m b e r f r o m the t e s t s t h a t y o u j u s t c o m p l e t e d  t o p o l o g i c a l d i s t a n c e will not e q u a l geometric We  displayed  that  distance.  will now explore the features of the interface y o u will  use.  RSN-NoOV T h i s i n t e r f a c e e n a b l e s y o u t o e x p l o r e the d a t a s e t u s i n g a v i e w w h i c h y o u c a n n a v i g a t e u s i n g p a n a n d z o o m a c t i o n s . T h e v i e w uses t h e m e t a p h o r o f s t r e t c h i n g and  s q u i s h i n g a r u b b e r sheet  with  its b o r d e r s t a c k e d d o w n .  Note  that  the  c o l o r e d n o d e s a r e v i s i b l e a t a l l t i m e s , even if t h e y a r e s q u i s h e d t o t h e edges o f the  view. The  left, m o u s e b u t t o n w i l l a l l o w y o u to d r a g o u t a b o x , t h e c o n t e n t s o f w h i c h  w i l l (ill t h e r e d b o x .  T h e rest o f t h e tree w i l l t h e n b e s q u i s h e d a r o u n d the r e d  box b u t will r e m a i n visible at all times.  Ask participant You  c a n z o o m o u t b y d r a g g i n g out. a b o x w h i c h is l a r g e r t h a n t h e r e d b o x .  Ask participant The  to try dragging out a box. to try zooming out.  r i g h t m o u s e b u t t o n w i l l a l l o w y o u to p a n h o r i z o n t a l l y a n d v e r t i c a l l y  w i t h i n t h e v i e w u s i n g e i t h e r h o r i z o n t a l o r v e r t i c a l d r a g m o t i o n s , w h i c h w i l l let you  fine t u n e y o u r s e l e c t i o n .  Ask participant  to try panning.  Appendix B. Study 2 Training Protocol  83  Y o u c a n use t h e c o l o r e d n o d e s as v i s u a l a n c h o r s t o h e l p m a i n t a i n o r i e n t a t i o n while p e r f o r m i n g navigation actions.  A s y o u z o o m or p a n . y o u c a n m o n i t o r the  l o c a t i o n a n d size of the colored n o d e s , w h i c h will give y o u a n i d e a o f w h a t  path  t o f o l l o w a n d h o w m u c h f a r t h e r y o u h a v e to go.  PZN-NoOV T h i s i n t e r f a c e e n a b l e s y o u to e x p l o r e navigate using pan and zoom  the dataset using a view w h i c h y o u can  actions.  T h e left m o u s e b u t t o n w i l l a l l o w y o u t o d r a g o u t a b o x . t h e c o n t e n t s o f w h i c h w i l l t h e n z o o m t o fill t h e v i e w c o m p l e t e l y  Ask participant  to try zooming in.  O n c e y o u are zoomed pan  .  in. y o u m a y h o l d down the right m o u s e b u t t o n  i n a n y d i r e c t i o n . Y o u cannot, p a n if y o u a r e z o o m e d o u t  Ask participant  and  entirely.  to try panning.  H o l d i n g d o w n the middle mouse b u t t o n a n d d r a g g i n g the mouse t o w a r d y o u will allow y o u to z o o m out.  A s y o u z o o m out. y o u m a y also d r a g the  mouse  in t h e o p p o s i t e d i r e c t i o n to z o o m b a c k i n . b u t o n l y t o t h e e x t e n t t h a t y o u first b e g a n to z o o m  out.  Ask participant  to try zooming out.  If a m a r k e d n o d e is not c u r r e n t l y i n v i e w , a c o l o r e d a r c w i l l a p p e a r a t  the  b o r d e r o f t h e d e t a i l v i e w , i n d i c a t i n g t h e d i r e c t i o n a n d d i s t a n c e f r o m y o u r current, f o c u s b o x t o t h e m a r k e d n o d e . T h e a r c is part, o f a c i r c u l a r r i n g t h a t s u r r o u n d s , a n y m a r k e d n o d e w h i c h is c u r r e n t l y o f f - s c r e e n . t h e c o l o r o f t h e m a r k e d n o d e it r e p r e s e n t s .  T h e color of the arc  indicates  O n c e a m a r k e d n o d e is v i s i b l e  on  screen, the arc will disappear. Y o u c a n use t h e a r c s as v i s u a l a n c h o r s to h e l p m a i n t a i n o r i e n t a t i o n o f m a r k e d nodes while p e r f o r m i n g navigation actions.  A s y o u z o o m out or p a n . y o u can  m o n i t o r t h e s h a p e a n d size o f t h e a r c . w h i c h w i l l g i v e y o u a n i d e a o f w h a t t o follow a n d h o w m u c h f a r t h e r y o u h a v e t o g o .  path  Appendix B. Study 2 Training Protocol  84  RSN+OV T h i s i n t e r f a c e e n a b l e s y o n to e x p l o r e t h e d a t a s e t u s i n g t w o v i e w s w h i c h y o u c a n navigate through using pan a n d z o o m actions. T h e larger view will display detailed i n f o r m a t i o n a b o u t parts of the  dataset.  T h i s v i e w uses t h e m e t a p h o r o f s t r e t c h i n g a n d s q u i s h i n g a r u b b e r s h e e t w i t h its b o r d e r s t a c k e d d o w n . N o t e t h a t t h e c o l o r e d n o d e s a r e v i s i b l e at a l l t i m e s ,  even  if t h e y a r e s q u i s h e d t o t h e edges o f t h i s v i e w . The  smaller view  will p r o v i d e y o u w i t h a n overview  of the  dataset,  i n d i c a t e w h e r e i n t h e d a t a s e t t h e d e t a i l v i e w is at a n y g i v e n t i m e .  This  and view  d o e s not use t h e r u b b e r sheet m e t a p h o r . T h e left m o u s e b u t t o n w i l l allow- y o u t o d r a g o u t a b o x , t h e c o n t e n t s o f w h i c h w i l l fill the r e d b o x .  T h e rest o f t h e t r e e w i l l t h e n b e s q u i s h e d a r o u n d t h e r e d  b o x but will r e m a i n visible at all times.  Ask participant  to try zooming in in the detail view.  Y o u c a n z o o m o u t b y d r a g g i n g o u t a b o x w h i c h is l a r g e r t h a n t h e r e d b o x .  Ask participant The  to try zooming out in the detail view.  right m o u s e  b u t t o n w i l l a l l o w y o u to p a n h o r i z o n t a l l y a n d v e r t i c a l l y  w i t h i n the v i e w u s i n g e i t h e r a h o r i z o n t a l o r v e r t i c a l d r a g m o t i o n s , w h i c h w i l l let y o u fine t u n e y o u r s e l e c t i o n .  Ask participant  to try panning in the detail view.  In t h e s m a l l e r v i e w , the left m o u s e b u t t o n w i l l a l l o w y o u z o o m i n t o a n a r e a by d r a g g i n g out a b o x which will b e c o m e the new contents of the r e d b o x in the larger view.  Ask participant  to try zooming in overview.  Y o u c a n also h o l d d o w n the r i g h t m o u s e b u t t o n while inside the red b o x in t h e s m a l l e r v i e w , a n d m o v e it w i t h i n t h e v i e w u s i n g a series o f d r a g a c t i o n s .  Ask participant  to try panning in overview.  Y o u c a n use t h e c o l o r e d n o d e s as v i s u a l a n c h o r s t o h e l p m a i n t a i n o r i e n t a t i o n while performing navigation actions.  A s y o u z o o m o r p a n . y o u c a n m o n i t o r the  l o c a t i o n a n d s i z e o f t h e c o l o r e d n o d e s , w h i c h w i l l g i v e y o u a n idea o f w h a t p a t h  Appendix B. Study 2 Training Protocol  85  t o follow a n d h o w m u c h f a r t h e r y o u h a v e t o g o .  PZN+OV T h i s interface enables  y o u to e x p l o r e the d a t a s e t u s i n g two v i e w s w h i c h y o u  can navigate t h r o u g h using p a n a n d z o o m actions. detailed i n f o r m a t i o n a b o u t parts of the dataset.  T h e larger v i e w will display  T h e smaller view will provide  y o u w i t h a n o v e r v i e w o f t h e d a t a s e t . a n d i n d i c a t e w h e r e i n the d a t a s e t t h e d e t a i l v i e w is at a n y g i v e n t i m e . T h e left m o u s e b u t t o n w i l l a l l o w y o u to d r a g o u t a b o x . t h e c o n t e n t s o f w h i c h w i l l t h e n z o o m t o fill t h e l a r g e r v i e w  Ask participant  to try zooming  completely.  in the detail  view.  O n c e y o u are z o o m e d in. y o u m a y h o l d d o w n the right mouse b u t t o n a n d pan  in a n y d i r e c t i o n . Y o u c a n n o t p a n if y o u a r e z o o m e d o u t e n t i r e l y .  Ask participant  to try panning  in tl\e detail  view.  H o l d i n g d o w n t h e m i d d l e m o u s e b u t t o n a n d d r a g g i n g the m o u s e t o w a r d y o u w i l l allow y o u to z o o m o u t .  A s y o u z o o m o u t . y o u m a y also d r a g t h e  mouse  in the o p p o s i t e d i r e c t i o n t o z o o m b a c k i n . b u t o n l y t o the e x t e n t t h a t y o u first b e g a n to z o o m o u t .  Ask participant  to try zooming  out in the detail  view.  In the s m a l l e r v i e w , t h e left m o u s e b u t t o n w i l l a l l o w y o u z o o m i n t o a n a r e a by d r a g g i n g o u t a b o x w h i c h will b e c o m e the new extent of y o u r d e t a i l view.  Ask participant  lo try zooming  in  overview.  Y o u c a n a l s o h o l d d o w n t h e r i g h t m o u s e b u t t o n w h i l e i n s i d e t h e r e d b o x in t h e s m a l l e r v i e w , a n d m o v e it w i t h i n t h e v i e w u s i n g a series o f d r a g a c t i o n s .  Ask participant  to try panning  in  overview.  If a m a r k e d n o d e is n o t c u r r e n t l y in v i e w , a c o l o r e d a r c w i l l a p p e a l ' at  the  b o r d e r of t h e d e l a i l v i e w , i n d i c a t i n g t h e d i r e c t i o n a n d d i s t a n c e f r o m y o u r c u r r e n t focus b o x to t h e m a r k e d n o d e . T h e a r c is p a r t o f a c i r c u l a r r i n g t h a t s u r r o u n d s any  m a r k e d n o d e w h i c h is c u r r e n t l y o f f - s c r e e n .  t h e c o l o r o f t h e m a r k e d n o d e it r e p r e s e n t s .  T h e color of the arc indicates  O n c e a m a r k e d n o d e is v i s i b l e o n  Appendix B. Study 2 Training Protocol  86  screen, the arc will d i s a p p e a r . . Y o u c a n use t h e a r c s as v i s u a l a n c h o r s t o h e l p m a i n t a i n o r i e n t a t i o n o f m a r k e d nodes while performing navigation actions.  A s y o u z o o m out or p a n , y o u can  m o n i t o r t h e s h a p e a n d size o f t h e a r c . w h i c h w i l l g i v e y o u a n i d e a o f w h a t p a t h to f o l l o w a n d h o w m u c h f a r t h e r y o u h a v e to g o .  A l l interfaces D o y o u have any questions about this interface? T h e R k e y c a n b e p r e s s e d to reset y o u r c u r r e n t v i e w t o its i n i t i a l s t a r t u p state. T h e E S C k e y c a n b e p r e s s e d d u r i n g a b o x d r a g a c t i o n to c a n c e l y o u r c u r r e n t drag. A l l t h e c o n t r o l s I j u s t s h o w e d y o u a r e a l s o l i s t e d at t h e left o f t h e w i n d o w i n case y o u need a r e m i n d e r . A t t h e t o p o f t h e w i n d o w is t h e t a s k y o u w i l l p e r f o r m i n t h i s e x p e r i m e n t . Y o u w i l l n e e d t o d e t e r m i n e w h e t h e r t h e p u r p l e n o d e is t o p o l o g i c a l ! } ' c l o s e r t o t h e b l u e n o d e o r t h e g r e e n n o d e in t h e t r e e . T h e t a s k w i l l n e v e r c h a n g e , b u t t h e l o c a t i o n o f the m a r k e d n o d e s w i l l w i t h e a c h t a s k .  Y o u c a n n o t s k i p o r go b a c k  to p r e v i o u s l y a n s w e r e d q u e s t i o n s . N o t e that the t o p o l o g i c a l distances to the blue n o d e a n d the green n o d e will n e v e r b e e q u a l , b u t t h e y m a y be close.  If it s e e m s as t h o u g h t h e y a r e e q u a l ,  p e r f o r m m o r e n a v i g a t i o n , a n d y o u w i l l d i s c o v e r t h a t t h e y a r e different f r o m e a c h other. N o t e t h a t t h e r e is o n l y o n e p a t h b e t w e e n a n y t w o n o d e s i n t h e t r e e . You  c a n use t h i s p e n / p e n c i l a n d sheet  cal distances between  of p a p e r to write d o w n  topologi-  n o d e s so t h a t y o u d o n ' t h a v e t o r e m e m b e r t h e m as y o u  p e r f o r m i n g the task. W h e n y o u a r e r e a d y , select t h e a p p r o p r i a t e a n s w e r a n d c l i c k o n t h e s u b m i t b u t t o n . T h i s w i l l a l l o w y o u to m o v e o n t o t h e n e x t q u e s t i o n . W e want, to e m p h a s i z e that we a r e e v a l u a t i n g t h e s y s t e m a n d n o t y o u r a b i l i t y  Appendix B. Study 2 Training Protocol  87  t o use it. F o r t h i s r e a s o n , y o u w i l l r e c e i v e n o i n d i c a t i o n o f w h e t h e r y o u r a n s w e r is c o r r e c t . T h e r e is n o t i m e l i m i t for c o m p l e t i n g t h e s e t a s k s . T a k e as m u c h t i m e as y o u n e e d t o e n s u r e t h a t y o u r a n s w e r is c o r r e c t , b u t d o w o r k as efficiently as y o u c a n .  RSN-NoOV A  g o o d s t r a t e g y for u s i n g t h i s i n t e r f a c e is t o d r a w o u t l o n g t h i n b o x e s .  w i l l h e l p y o u t o see  t h e l a r g e r tree i n m o r e d e t a i l .  This  It's o f t e n h e l p f u l t o d r a w  l o n g h o r i z o n t a l boxes to z o o m into the details o f the dataset, a n d to d r a w l o n g v e r t i c a l b o x e s to e x p a n d a r e a s t h a t a r e s q u i s h e d v e r t i c a l l y .  Demonstrate this, then ask participant  to do it.  A n o t h e r useful s t r a t e g y is to reset t h e i n t e r f a c e w h e n y o u h a v e f o u n d o n e o f the topological distances before y o u m o v e onto a n o t h e r distance.  Demonstrate this, then ask participant  to do it.  PZN-NoOV A  g o o d s t r a t e g y for u s i n g t h i s i n t e r f a c e is t o d r a w o u t l o n g t h i n b o x e s .  This  w i l l h e l p y o u to see t h e l a r g e r tree i n m o r e d e t a i l .  Demonstrate this. then, ask participant  to do it. (  O n c e y o u h a v e z o o m e d in to t h e a r e a a r o u n d e i t h e r t h e b l u e o r t h e  green  n o d e , y o u c a n c o u n t t h e n u m b e r o f n o d e s o n t h e p a t h t h a t a r e c l o s e t o it.  Then  you  c a n s l o w l y z o o m o u t a n d , as y o u see m o r e n o d e s o n t h e p a t h t o t h e p u r p l e  node, a d d t h e m to y o u r count.  Demonstrate this, then ask participant  to do it.  A d d i t i o n a l l y , y o u c a n reset t h e i n t e r f a c e w h e n y o u h a v e f o u n d o n e o f  the  topological distances before y o u move onto another distance.  RSN+OV A  g o o d s t r a t e g y for u s i n g t h i s i n t e r f a c e is t o d r a w o u t l o n g t h i n b o x e s .  w i l l h e l p y o u to see  t h e l a r g e r tree i n m o r e d e t a i l .  This  It's o f t e n h e l p f u l t o d r a w  Appendix B. Study 2 Training Protocol  88  long h o r i z o n t a l boxes to z o o m into the details o f the dataset. a n d to d r a w l o n g v e r t i c a l b o x e s to e x p a n d a r e a s t h a t are s q u i s h e d v e r t i c a l l y .  Demonstrate  this, then ask participant to do it.  A n o t h e r u s e f u l s t r a t e g y is t o first z o o m i n t o t h e a r e a a r o u n d e i t h e r t h e b l u e o r t h e g r e e n n o d e u s i n g t h e s m a l l v i e w . T h e n y o u c a n ' u s e e i t h e r v i e w to e x p l o r e the p a t h to the p u r p l e node. in either view.  N o t e that, y o u c a n c o u n t n o d e s a l o n g t h e p a t h  If y o u n e e d t o m a k e s m a l l a d j u s t m e n t s , y o u c a n p a n : for l a r g e r  movements, y o u can z o o m in either view.  Demonstrate You  this, then ask participant to do it:  c a n also reset t h e i n t e r f a c e w h e n y o u h a v e f o u n d o n e o f t h e t o p o l o g i c a l  distances before y o u m o v e o n t o another distance.  Demonstrate this, then ask participant to do it. We  s t r o n g l y s u g g e s t y o u use these s t r a t e g i e s as y o n are a n s w e r i n g t h e q u e s -  tions.  PZN+OV A  g o o d s t r a t e g y for u s i n g t h i s i n t e r f a c e is to d r a w o u t l o n g t h i n b o x e s .  This  w i l l h e l p y o u to see t h e l a r g e r tree i n m o r e d e t a i l . .  Demonstrate  this, then ask participant to do it.  A n o t h e r useful s t r a t e g y is t o first, z o o m i n t o t h e a r e a a r o u n d e i t h e r t h e b l u e or t h e g r e e n n o d e u s i n g t h e s m a l l v i e w . T h e n y o u c a n use e i t h e r v i e w to e x p l o r e t h e p a t h to t h e p u r p l e n o d e . in e i t h e r v i e w .  N o t e that y o u c a n count nodes a l o n g the p a t h  If y o u n e e d t o make s m a l l a d j u s t m e n t s , y o u c a n p a n : for l a r g e r  movements, y o u can z o o m in either view.  Demonstrate  this, then ask participant to do it.  A d d i t i o n a l l y , y o u c a n reset t h e i n t e r f a c e w h e n y o u h a v e f o u n d o n e o f t h e topological distances before y o u move onto a n o t h e r distance.  Demonstrate this, then ask participant to do it.  Appendix B. Study 2 Training Protocol  89  A l l interfaces W e s t r o n g l y s u g g e s t y o u use t h e s e s t r a t e g i e s as y o u a r e a n s w e r i n g t h e q u e s t i o n s .  Appendix C  Study 1 Questionnaires  Appendix  C. Study 1 Questionnaires  UBC T H E UNIVERSITY OF BRITISH C O L U M B I A Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  Interface # 1  Subject  #  91  Appendix C. Study 1 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  Group  O 20 - 29 O 3 0 - 39 O 4 0 - 49 O50 +  2.  Gender  O  Male  O  Female  3.  Education  I  O  S o m e high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  S o m e g r a d u a t e or p r o f e s s i o n a l s c h o o l  O  C o m p l e t e d postgraduate degree .  4.  Computer  Oo-to O 10 - 20 O 20 - 30 O 30 - 4 0 O 40 - 50 Q50  +  Usage  (hours per  week):  92  Appendix C. Study 1 Questionnaires  93  Part 2  W i t h respect to the visualization y o u worked w i t h ,  a) p l e a s e i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  = Agree  S A == S t r o n g l y  Agree  Appendix C. Study 1 Questionnaires  94  O S D  O D  O N  O A  OSA  O SD  O D  O N  O A  OSA  was  O SD  O D  O  O A  O SA  be  O SD  O D  O N  O A  OSA  O S D  O D  O  O A  OSA  O SD  O D  O N  O A  OSA  O SD  O D  O N  O A  OSA  O SD  O D  O  N  O A  OSA  6  O D  O  N  O A  OSA  I f o u n d t h i s v i s u a l i z a t i o n t o b e efficient for c o m p l e t i n g t h e t a s k s . N a v i g a t i n g t h r o u g h t h e d a t a was easy to do. Locating  coloured  nodes  N  easy. 1 found  t h i s v i s u a l i z a t i o n to  frustrating. C o m p a r i n g topological distances  N  b e t w e e n n o d e s w a s easy. I f o u n d it e a s y to get  lost in t h i s  visualization. Using  two  coloured  focus  boxes  h e l p e d m e to c o m p l e t e t h e t a s k . Being  able  to  see  compressed  c o l o u r e d n o d e s a r o u n d t h e edges o f t h e v i e w m a d e t h e t a s k easier. I enjoyed using this visualization.  SD  b) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u like'!  c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u  dislike?  Appendix C. Study 1 Questionnaires  95  d ) P l e a s e use t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e s t r a t e g i e s ( o t h e r t h a n t h o s e y o u w e r e s h o w n at t h e b e g i n n i n g o f t h e e x p e r i m e n t ) t h a t y o u b e l i e v e w o u l d h a v e w o r k e d b e t t e r for y o u .  e) P l e a s e use t h i s s p a c e t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e e x p e r i m e n t or the v i s u a l i z a t i o n .  T h a n k y o u for y o u r t i m e !  Appendix C. Study 1 Questionnaires  UBC T H E UNIVERSITY OF BRITISH C O L U M B I A  Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  s  Subject  Interface # 2  #  96  Appendix C. Study 1 Questionnaires Part 1  1. A g e G r o u p O  19 a n d u n d e r  O 20 O 30 0  - 29 - 39  40-49  O50 +  2. G e n d e r O  Male  O  Female  3. E d u c a t i o n O  Some high school  O  C o m p l e t e d high school  O  Some post-secondary  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  Some g r a d u a t e or professional  O  Completed postgraduate  education  school  degree  4. C o m p u t e r U s a g e ( h o u r s p e r w e e k ) : O0-1Q  O 10O 20 O 30 O 40 Q50  +  20 30 40 50  97  Appendix C. Study 1 Questionnaires  98  Part 2  W i t h respect to the visualization y o u worked w i t h ,  a) p l e a s e i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  = Agree  S A == S t r o n g l y A g r e e  Appendix C. Study 1 Questionnaires I found this visualization to be ef-  99  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  0 SD  OD  ON  OA  OSA  1 found this visualization to be O S D  OD  ON  OA  OSA  O SD  OD  ON  OA  OSA  O SD  OD  ON  OA  OSA  O SD  OD  ON  OA  OSA  O  OD  0 N  OA  OSA  OD  O N  OA  OSA  ficient for completing the tasks. Navigating through the data was easy to do. Locating  coloured  nodes was  easy.  frustrating. Comparing topological distances between nodes was easy. I found it easy to get lost in this visualization. Using two coloured focus boxes helped me to complete the task. The coloured arcs made naviga-  SD  tion easier. I enjoyed using this visualization.  OSD  b) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u like?  c) W h a t p a r t i c u l a r a s p e c t ( s ) of t h i s v i s u a l i z a t i o n d i d y o u dislike?  Appendix C. Study 1 Questionnaires  100  d) P l e a s e use t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e s t r a t e g i e s ( o t h e r t h a n t h o s e y o u w e r e s h o w n at t h e b e g i n n i n g o f t h e e x p e r i m e n t ) that y o u believe w o u l d have worked b e t t e r for y o u .  e) P l e a s e use t h i s s p a c e t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e experiment or the visualization.  T h a n k y o u for y o u r t i m e !  Appendix C. Study 1 Questionnaires  101  UBC | T H E  U N I V E R S I T Y  O F BRITISH  C O L U M B I A  Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n T e c h n i q u e s  Interface # 3  Subject  #  Appendix C. Study 1 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  O 20 O 30 O 40  Group  - 29 - 39 - 49  O50 +  2.  Gender  O  Male  O  Female  3.  Education  O  S o m e high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  Some graduate or professional school  O  Completed postgraduate  4.  Computer Usage  O 0 - 10  O 10 O 20 O 30 O 40 O 50  - 20 - 30 - 40 - 50 +  degree  (hours per  week):  102  Appendix C. Study 1 Questionnaires  103  Part 2  W i t h r e s p e c t to t h e v i s u a l i z a t i o n y o u w o r k e d w i t h ,  a) p l e a s e i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  = Agree  S A == S t r o n g l y A g r e e  Appendix C. Study 1 Questionnaires  OA  OSA  ON  OA  OSA  OD  O  OA  OSA  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  O SD  OD  O  OA  OSA  0 SD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  O SD  OD  ON  OA  OSA  OSD  OD  O  OA  OSA  0 SD  OD  O  OSD  OD  was  OSD  be  C o m p a r i n g topological distances  I f o u n d t h i s v i s u a l i z a t i o n t o b e ef-  104  N  f i c i e n t for c o m p l e t i n g t h e t a s k s . N a v i g a t i n g t h r o u g h the d a t a was easy to do. Locating  coloured  nodes  N  easy. I  found  t h i s v i s u a l i z a t i o n to  frustrating.  b e t w e e n n o d e s w a s easy. I f o u n d it e a s y t o g e t lost i n t h i s  N  visualization. The  presence of the smaller view  m a d e t h e task e a s i e r . Using  two  coloured  focus  boxes  h e l p e d m e to c o r t i p l e t e t h e t a s k . Being  able  to  see  compressed  c o l o u r e d nodes a r o u n d the edges o f the v i e w m a d e the task easier. I enjoyed using this visualization.  N  b) W h a t p a r t i c u l a r aspect(s) o f this visualization d i d y o u  c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u  like?  dislike?  Appendix C. Study 1 Questionnaires  105  d ) P l e a s e use t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e s t r a t e g i e s ( o t h e r t h a n those y o u w e r e s h o w n at t h e b e g i n n i n g o f t h e e x p e r i m e n t ) t h a t y o u b e l i e v e w o u l d h a v e w o r k e d b e t t e r for y o u .  e) P l e a s e use t h i s space t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e e x p e r i m e n t or t h e v i s u a l i z a t i o n .  T h a n k y o u for y o u r t i m e !  Appendix C. Study 1 Questionnaires  106  UBC I T H E UNIVERSITY OF BRITISH C O L U M B I A  Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  Interface # 4  Subject  #  Appendix C. Study 1 Questionnaires Part  1  1.  Age  Group  O  19 a n d u n d e r  O 20 - 29 O 30 - 39 O 40 - 49 O 50 + 2.  Gender  O  Male  O  Female  3.  Education  O  Some high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  Some g r a d u a t e or professional school  O  C o m p l e t e d p o s t g r a d u a t e degree  4.  Computer Usage  O o - io  O 10 - 20 O 20 - 30 O 30 - 40 O 40 - 50 O50 +  (hours per  week):  107  Appendix C. Study 1 Questionnaires  108  Part 2  W i t h respect to the visualization you worked w i t h ,  a) please i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  = Agree  S A == S t r o n g l y A g r e e  Appendix C. Study 1 Questionnaires  109  OA  O'SA  ON  O A  OSA  OD  O  N  O A  OSA  OSD  OD  O  N  OA  OSA  OSD  OD  O  N  O A - OSA  OSD  OD  O  N  OA  OSA  OSD  OD  O  N  OA  OSA  OSD  OD  O  N  O A  OSA  naviga-  OSD  OD  O  N  O A  OSA  I enjoyed using this visualization.  OSD  OD  O  N  OA  OSA  OSD  OD  O  O SD  OD  was  OSD  be  C o m p a r i n g topological distances  I f o u n d t h i s v i s u a l i z a t i o n t o be ef-  N  f i c i e n t for c o m p l e t i n g t h e t a s k s . N a v i g a t i n g t h r o u g h the d a t a was easy to do. Locating  coloured  nodes  easy. I  found  t h i s v i s u a l i z a t i o n to  frustrating.  b e t w e e n n o d e s w a s easy. I f o u n d it e a s y t o get lost i n t h i s visualization. T h e presence of the smaller view m a d e the task easier. Using  two  coloured  focus  boxes  h e l p e d m e to c o m p l e t e t h e t a s k . The  coloured arcs m a d e  t i o n easier.  Appendix D  Study 2 Questionnaires  \  Appendix D.  Study 2 Questionnaires  111  UBC T H E UNIVERSITY OF BRITISH C O L U M B I A Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  Interface  Subject  #  1  Appendix D. Study 2 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  O 20 O 30 O 40  Group  - 29 - 39 - 49  O50 +  2.  Gender  O  Male  O  Female  3.  Education  O  Some high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  S o m e g r a d u a t e or professional school  O  Completed postgraduate  4.  Computer Usage  Oo - I O O 1 0 - 20 O 20 - 30 O 30 - 40 O 40 - 50 O50 +  degree  (hours per  week):  112  Appendix D. Study 2 Questionnaires  113  Part 2  W i t h respect to t h e visualization y o u worked w i t h ,  a) p l e a s e i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  Agree  S A = Strongly Agree :  OSD  OD  O  N  OA  OSA  O SD  OD  O N  OA  OSA  was  OSD  OD  O  N  OA  O SA  be  OSD  OD  O N  OA  0 SA  C o m p a r i n g topological distances  OSD  OD  ON  OA  OSA  I f o u n d it e a s y to g e t l o s t .  OSD  OD  ON  OA  OSA  Being  O SD  OD  ON  OA  OSA  OSD  OD  O N  OA  OSA  I f o u n d t h i s v i s u a l i z a t i o n t o b e efficient for c o m p l e t i n g t h e t a s k s . N a v i g a t i n g t h r o u g h t h e d a t a was easy to do. Locating  coloured  nodes  easy. I found  t h i s v i s u a l i z a t i o n to  frustrating.  b e t w e e n n o d e s w a s easy.  able  to  see  compressed  c o l o u r e d n o d e s a r o u n d t h e edges o f t h e v i e w m a d e t h e t a s k easier. 1 enjoyed using this v i s u a l i z a t i o n .  Appendix D. Study 2 Questionnaires  114  b) W i t h r e s p e c t t o t h e v i s u a l i z a t i o n y o u w o r k e d w i t h , p l e a s e a n s w e r t h e f o l l o w i n g q u e s t i o n s b y m a r k i n g a n ' X ' a l o n g t h e scale b e s i d e t h e corresponding question.  H o w m u c h mental andperceptual activity was required to complete the task (e.g., looking, searching, thinking, deciding, calculating,  ~ ~ 1  MENTAL DEMAM) 1 > 1 i t i  i 1 j 1 . 11 | ,  i  i  i t  s  i i  i  i  1  ! i  complete the task(e.g., moving the mouse, dragging, clicking, pressing keys, etc.)?  H o w much time pressure did y o u feel due to the rate or pace at w h i c h the tasks or task elements occurred?  jH ow hard d i d y o u have to work (m entally and physically) to accomplish y o u r level o f performance?  H o w successful do y o u think y o u were in accomplishing the goals of the task set b y the experimenter (or yourself)?  PHYSICAL CeMAND  1  I 1i 1I 1 I 1 1 i 1 i 1 i 1 i I i L I 1 ! ! ,l„,l I i 1 ! ! i E ! 1 M 1 I t ] Hie). | Lor TEMPORAL DEMAND  1i 1I 1  l>ow  i  I i ! i  1 111 i  i  I i 1i  1  annoyed versus secure, gratified, content, relaxed and complacent did y o u feel during the task?  i  11111 Hit).  ! |  EFFORT  1 i 1i I  Lew  i 1  PERFORMANCE  1I I1 11 !1 I1 1 11 1  1  1  11  11  1 11  Cood H o w insecure, discouraged, irritated, stressed and  i  Hit* !  remembering, etc.)? H o w m u c h physical activity was required to  1  i 1 i 1111(111 i  i  llich j  11 11 11 1  11 1 1  1  1 I I1 Poor  |  FRUSTRATION l  1  1  Low  t  i  l  1! 111  1  l  1  11 1  i I ! i • 1 1 1 1 1 1 1 1 I : H*>> |  1  Appendix D. Study 2 Questionnaires  115  c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u like?  d) W h a t p a r t i c u l a r aspect(s) o f t h i s v i s u a l i z a t i o n d i d y o u dislike?  e) P l e a s e use t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e s t r a t e g i e s ( o t h e r t h a n those y o u w e r e s h o w n a t t h e b e g i n n i n g o f t h e e x p e r i m e n t ) t h a t y o u b e l i e v e w o u l d h a v e w o r k e d b e t t e r for y o u .  f) P l e a s e use t h i s s p a c e t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e experiment or the visualization.  T h a n k y o u for y o u r t i m e !  Appendix D.  Study 2 Questionnaires  116  UBC T H E UNIVERSITY OF BRITISH C O L U M B I A Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n T e c h n i q u e s  Interface # 2  Subject  #  Appendix D. Study 2 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  O 20 O 30 O 40 -  Group  29 39 49  O50 +  2.  Gender  O  Male  O  Female  3.  Education  O  Some high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  Some g r a d u a t e or professional school  O  C o m p l e t e d p o s t g r a d u a t e degree  4.  Computer  Oo- io O10-20  O 20 O 30 O 40 O50 +  30 40 50  Usage  (hours per  week):  117  Appendix D. Study 2 Questionnaires  118  Part 2  W i t h respect to the visualization y o u worked w i t h ,  a) please i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: S D == S t r o n g l y D i s a g r e e D  = Disagree  N  = Neutral  A  = Agree  S A == S t r o n g l y  Agree  0 SD O D  ON  OA  OSA  was  0 SD O D  0 N OA  OSA  was  O SD  OD  ON  OA  OSA  0 SD O D  ON  OA  OSA  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  naviga-  O SD  OD  ON  OA  OSA  1 enjoyed using this visualization.  OSD  OD  ON  OA  OSA  1 f o u n d t h i s v i s u a l i z a t i o n t o b e efficient for c o m p l e t i n g t h e  tasks.  N a v i g a t i n g t h r o u g h the d a t a easy t o d o . Locating  coloured  nodes  easy. I found  this visualization  to  be  frustrating. C o m p a r i n g topological  distances  b e t w e e n n o d e s w a s easy. I f o u n d it e a s y to get The  coloured  lost.  arcs m a d e  tion easier.  Appendix D. Study 2 Questionnaires  119  b) W i t h respect to t h e v i s u a l i z a t i o n y o u worked w i t h , please answer t h e f o l l o w i n g q u e s t i o n s b y m a r k i n g a n ' X ' a l o n g t h e scale b e s i d e t h e corresponding question.  H o w much mental and perceptual activity was  I ME NT AL DE MAM)  requiredto complete the task (e.g., looking,  j  searching, thinking, deciding, calculating,  \  remembering, etc.)?  |  H o w much physical activity was required to  j  complete the task(e.g., moving the mouse,  I  dragging, clicking, pressing keys, etc.)?  \  i  H o w much time pressure did y o u feel due to the  |  rate or pace at w h i c h the tasks or task elements  j  occurred?  j  1  1 l1 I I 1 1 I 1 I i1 tI 1 1 !1 !1 I F1l )i tI ii i! ii i1 ii i1 t  PHYSICAL DEMAND  111111 1I1 1 ! i 1i 1 1..I I 1 „ I.J 1 i i LJ...I L.I.. 1  1  i ! i  TEMPORAL DEMAND  11 Low  H o w hard d i d y o u have to work (mentally and  [ EFFORT  physically) to accomplish your level o f  j  performance?  ]  1  1  1  t1 1  1  11  1I1  1  1  1 1It  1i 1 i  1 1 Low  1  1  j  1 1 (11 11 !1 iI 1 1 1 111 1 l l1 11  Cood |How insecure, discouraged, irritated, stressed and! jannoyed versus secure, gratified, content^ relaxed j (and complacent did y o u feel during the task? |  1 h1 h  ! i  1  Hi* (  h l i l  S PERFORMANCE  accomplishing the goals of the task set b y the e xp erim enter (or yours elf)?  1  J J Hi*  Low  i  H o w successful do y o u think y o u were i n  1  Low  j i  1 11 1  1  I 1 Poor  1 1 i  FRUSTRATION t i 111 Low  l  1 1 )  l  1  l 1  1 t 1 1 i i F 1 1 1 I1 I 1 1 1 1 1 1 I 1 Hie* i  Appendix D. Study 2 Questionnaires  120  c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u like?  d) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u dislike?  e) P l e a s e use t h i s space t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e strategies (other t h a n those y o u were s h o w n at the b e g i n n i n g of t h e e x p e r i m e n t ) that y o u believe w o u l d have worked b e t t e r for y o u .  f) P l e a s e use t h i s space t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e experiment o r the visualization.  T h a n k y o u for y o u r t i m e !  Appendix D.  Study 2 Questionnaires  121  \VBC\ T H E UNIVERSITY OF BRITISH C O L U M B I A Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  Interface #  Subject  #  3  s  Appendix D. Study 2 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  O 20 O 30 O 40 O&0  Group  - 29 - 39 - 49 +  2.  Gender  O  Male  O  Female  3.  Education  O  Some high school  O  C o m p l e t e d high school  O  Some post-secondary education  O  C o m p l e t e d u n d e r g r a d u a t e degree  O  Some g r a d u a t e or professional school  O  C o m p l e t e d p o s t g r a d u a t e degree  4.  Computer Usage  O o - io  O 10 O 20 O 30 O 40  - 20 - 30 - 40 - 50  O50 +  (hours per  week):  122  Appendix D. Study 2 Questionnaires  123  Part 2  W i t h respect to the visualization you worked with, a) please indicate the extent to which you agree or disagree with the following statements: S D == Strongly Disagree D = Disagree N = Neutral A = Agree S A == Strongly Agree  OD  ON  O A  OSA  OSD  OD  O N  O A  OSA  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  OSD  OD  ON  OA  OSA  The presence of the smaller view O SD  OD  ON  OA  OSA  O SD - O D  0 N  OA  OSA  OSD  ON  OA  OSA  I found this visualization to be ef- O SD ficient for completing the tasks. Navigating through the data was easy to do. Locating coloured nodes was easy. I found this visualization to be frustrating. Comparing topological distances between nodes was easy. I found it easy to get lost. made the task easier. Being able to see compressed coloured nodes around the edges of the view made the task easier. I enjoyed using this visualization.  OD  Appendix D. Study 2 Questionnaires  124  b) W i t h r e s p e c t t o t h e v i s u a l i z a t i o n y o u w o r k e d w i t h , please a n s w e r t h e f o l l o w i n g q u e s t i o n s b y m a r k i n g a n ' X ' a l o n g t h e scale b e s i d e t h e corresponding question.  'How much mental and perceptual activity was jrequired to complete the task(e.g. looking, 7  isearching, thinking, deciding, calculating, remembering, etc.)? How much physical activity was required to complete the task(e.g., moving the mouse, dragging, clicking, pressing keys, etc.)?  M E N T A L DEMAND  11 Vow  1  1  1f 1  I  i  Hist.  PHYSICAL DEMAND  1 . 1. I i 1i 1 i  M i l l !  ! ! 1 Hi<*  Urn  'How much time pressure did you feel due to the Irate or pace at which the tasks or task elements Joccurred?  TEMPORAL DEMAND  IHow hard did you have to work (mentally and physically) to accomplish your level of performance?  EFFORT  How successful do you think you were in accomplishing the goals of the task set by the experimenter (or yourself)?  PERFORMANCE  11 Low  1I 1! 1I I 1 i 1 i 1i 1 ! i1  Hid.  1i 1i 1i I i ! i  i 1 i 1  i 11!1  Hfeh  Lor  1  i 1 i 1 i ! i  i  1  i  i  11 1 Poor  Cood  iHow insecure, discouraged, irritated, stressed and FRUSTRATION ]annoyed versus secure, gratified, contend relaxed 1 1 1111 Sand complacent did you feel during the task?  |  I 1i 1 i I  1  Low  1  1  1  1  i 1i  1i1  1  1  1  Rich  Appendix D. Study 2 Questionnaires  125  c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u like?  d ) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u dislike?  e) P l e a s e use t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e strategies (other t h a n those y o u were s h o w n a t the b e g i n n i n g of the experiment) that y o u believe w o u l d have w o r k e d b e t t e r for y o u .  f) P l e a s e use t h i s s p a c e t o m a k e any o t h e r c o m m e n t s a b o u t t h e experiment or the visualization.  T h a n k y o u for y o u r t i m e !  Appendix D.  Study 2 Questionnaires  126  UBC T H E UNIVERSITY OF BRITISH C O L U M B I A  Experimental Questionnaire  E v a l u a t i o n of I n f o r m a t i o n V i s u a l i z a t i o n Techniques  Interface # 4  Subject  #  Appendix D. Study 2 Questionnaires Part  1  1.  Age  O  19 a n d u n d e r  O 20 O 30 O 40 O 50  Group  - 29 - 39 - 49 +  2.  Gender  O  Male  O  Female  3.  Education  O  Some high school  O  C o m p l e t e d high school  "O  Some post-secondary  education  O  C o m p l e t e d undergraduate degree  O  Some g r a d u a t e or professional  O  Completed postgraduate  4.  Computer Usage  O o - io O 10 - 20 O 20 - 30 O 30 - 40 O 40 - 50 O50 +  school  degree  (hours p e r  week):  127  Appendix D. Study 2 Questionnaires  128  Part 2  W i t h respect to the visualization y o u w o r k e d w i t h , a) p l e a s e i n d i c a t e t h e e x t e n t t o w h i c h y o u agree o r d i s a g r e e w i t h t h e following statements: SD D  z  - Strongly Disagree  = Disagree Neutral  N  A = Agree S A == S t r o n g l y A g r e e  OSD  OD  ON  OA  OSA  was  OSD  OD  O  N  OA  OSA  was  OSD  OD  O  N  OA  OSA  be  OSD  OD  O  N  O  A  OSA  distances  OSD  OD  O  N  OA  OSA  OSD  OD  O  N  OA  O SA  OSD  OD  ON  OA  OSA  naviga-  OSD  OD  0  N  OA  OSA  1 enjoyed using this v i s u a l i z a t i o n .  OSD  OD  0  N  OA  OSA  I f o u n d t h i s v i s u a l i z a t i o n t o b e efficient for c o m p l e t i n g t h e  tasks.  N a v i g a t i n g t h r o u g h the d a t a e a s y to d o . Locating  coloured  nodes  easy. I  found  this visualization  to  frustrating. C o m p a r i n g topological b e t w e e n n o d e s w a s easy. I f o u n d it e a s y to get The  lost.  p r e s e n c e o f t h e s m a l l e r view-  m a d e the t a s k e a s i e r . The  coloured arcs m a d e  tion easier.  Appendix  D.  Study  2  Questionnaires  129  b) W i t h respect t o t h e v i s u a l i z a t i o n y o u w o r k e d w i t h , please answer the following questions b y m a r k i n g a n ' X ' along t h e scale beside t h e corresponding question.  IHow much mental and perceptual activity was •required to complete the task(e.g., looking, [searching, thinking, deciding, calculating, [remembering, etc)?  \ MENTAL DEMAND  I  1t I i 1  1  1  i  1  L  P H l ' a O U . DEMAND  [How much physical activity was required to Icomplete the task(e.g., moving the mouse, dragging, clicking, pressing keys, etc.)?  1  I  I  I  I  I  I I II  TEMPORAL DEMAND  How much time pressure did you feel due to the [rate orpace at which the tasks or task elements occurred?  1I  I  I  I  I  I  I  I  I  i  11 I i  11 1 i I  \  IHow hard did you have to work (mentally and jphysically) to accomplish your level of iperformance? How successfi.il do you think you were in accomplishing the goals of the task set by the experimenter (or yourself)?  M  I  N  I  M  I  I M  I  ! PERFORMANCE  !  i i 1111  M  I  I  I  u jHow insecure, discouraged, irritated, stressed and! FRUSTRATION [annoyed versus secure, gratified, content, relaxed j [and complacent did you feel during the task? j L! '  I  I I  M  l  M _ L Hid>  Appendix D. Study 2 Questionnaires c) W h a t p a r t i c u l a r a s p e c t ( s ) o f t h i s v i s u a l i z a t i o n d i d y o u  d) W h a t p a r t i c u l a r aspect(s) of this v i s u a l i z a t i o n d i d y o u  130  like?  dislike?  e) P l e a s e u s e t h i s s p a c e t o d e s c r i b e / i l l u s t r a t e a n y a l t e r n a t i v e strategies  ( o t h e r t h a n t h o s e y o u w e r e s h o w n at t h e b e g i n n i n g o f t h e  e x p e r i m e n t ) t h a t y o u b e l i e v e w o u l d h a v e w o r k e d b e t t e r for y o u .  f) P l e a s e use t h i s s p a c e t o m a k e a n y o t h e r c o m m e n t s a b o u t t h e e x p e r i m e n t or the visualization.  T h a n k y o u for y o u r t i m e !  

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