Revisiting Read Wear: Analysis, Design, and Evaluation of a Footprints Scrollbar Jason Alexander 1, Andy Cockburn 1, Stephen Fitchett 1, Carl Gutwin 2, Saul Greenberg 3 1 Dept. of Computer Science 2 Dept. of Computer Science 3 Dept. of Computer Science University of Canterbury University of Saskatchewan University of Calgary Christchurch, New Zealand Saskatoon, Canada Alberta, Canada {jason, andy, saf75} [email protected] [email protected] @cosc.canterbury.ac.nz ABSTRACT having attended to the thumb’s location during previous In this paper, we show that people frequently return to visits, remembering it, and reproducing it accurately. One previously-visited regions within their documents, and that or more of these activities can fail. In their comparison of scrollbars can be enhanced to ease this task. We analysed navigation in paper and electronic documents O’Hara and 120 days of activity logs from Microsoft Word and Adobe Sellen [25] observed that people use fingers to mark Reader. Our analysis shows that region revisitation is a document regions in paper documents for easy return, and common activity that can be supported with relatively short that equivalent methods are lacking when scrolling. They recency lists. This establishes an empirical foundation for conclude that scrolling is “irritatingly slow and distracting” the design of an enhanced scrollbar containing scrollbar and that people need “quicker, more effortless navigation” marks that help people return to previously visited [25], p.341. document regions. Two controlled experiments show that scrollbar marks decrease revisitation time, and that a large One way to improve support for revisitation is by number of marks can be used effectively. We then design augmenting the scrollbar region with scrollbar marks. Such an enhanced Footprints scrollbar that supports revisitation marks are not a new idea. Attribute-mapped scrollbars , with several features, including scrollbar marks and mark patented in 1990 [31], used coloured marks in the scrollbar thumbnails. Two further experiments show that the to draw attention to salient properties; scrollbars are well- Footprints scrollbar was frequently used and strongly suited to showing this information, as they provide an preferred over traditional scrollbars. overview of the entire document. Hill et al. [18] used a similar approach to denote the read wear that occurs with Author Keywords. use – the marks portray how often sections of the document Document revisitation, read wear, scrolling. have been read. However, their focus was on showing history of use, not on supporting revisitation. ACM Classification Keywords. Read-wear marks on the scrollbar offer a lightweight H.5. Information interfaces and presentation: User method for improving document revisitation compared to interfaces ( Interaction styles , screen design ). traditional scrolling: a mark shows a person where they have been, and provides a navigation cue to help them INTRODUCTION quickly return to that spot. However, the idea has not Scrollbars are a familiar widget common to graphical user caught on, and we are unaware of any system currently interfaces, and have become a standard idiom for view using it (although scrollbar marks are becoming common in navigation within documents. They are compact and IDEs for marking code errors or comments). conceptually simple, yet powerful, providing useful information about the viewport’s location and extent in a We believe the poor adoption of read-wear scrollbars is due larger information space. In particular, the scroll thumb’s to a lack of knowledge about how revisitation occurs in the spatial cue can help revisitation – returning to previously real world, how best to design a read-wear scrollbar, and visited document regions. For example, a user may know the potential benefits and harms of using it in realistic that “moving the thumb roughly four-fifths of the way systems. Consequently, we conducted several investigations down will bring me to the Results section”. to address these knowledge gaps. However, rapid and effective revisitation depends on people 1. How do people revisit document locations, and are current tools well used? We analysed logs from a 120- Cite as : Alexander, J., Cockburn, A., Fitchett, S., Gutwin, C., and day longitudinal study of document navigation in Greenberg, S. Revisiting Read Wear: Analysis, Design, and Evaluation of Microsoft Word and Adobe Reader, and draw three main a Footprints Scrollbar. Department of Computer Science and Software conclusions: that region revisitation is frequent, that Engineering. Tech Report #02/08. 2008. current revisitation tools other than the normal scrollbar 1 are used very little, and that short recency lists can immediate suboptimal strategies are favoured over more contain most locations that people will revisit. efficient long-term ones) suggests that people will often fail 2. Can scrollbar marks improve revisitation, and how many to place bookmarks, even when they can foresee the long marks should be used? We conducted two experiments to term advantage [1]. This is why our research interest lies test the performance of adding marks into the scrollbar. primarily in automatic revisitation support. One study demonstrates that marks can decrease Automatic revisitation tools have been developed to support revisitation time; the other shows that people can revisitation both between and within documents. Familiar successfully use a large number of marks. interface controls such as history lists, ‘Back/Forward’ 3. How can a realistic interface support revisitation? We buttons, and ‘Recent Document’ menus facilitate navigation designed our Footprints Scrollbar (Figure 5) to maximize between documents. These automatic revisitation tools support for revisitation, based on principles derived from minimally intrude on users’ activities: they silently record the log analysis and the two studies. actions, populate a data structure or visualisation, and 4. Is this support used effectively and is it preferred? We provide support when called on. Their primary evaluated the Footprints Scrollbar in two experiments: a disadvantages are that people may not understand the controlled lab study and a realistic usage study. The algorithm for recording or presenting events, and the event Footprints Scrollbar was frequently and successfully set may overwhelm or fail to match the interests of the user. used, improved users’ revisitation time, and was strongly For example, people often misunderstand the behaviour of preferred to traditional scrollbars. the web ‘Back’ button, causing frustration when items Overall, our investigations show that revisitation is worth cannot be revisited [12], and we have observed similar supporting, and that read wear – long known but little problems with missing items in ‘Recent Documents’ studied – is a valuable and usable technique for improving menus, and with user misunderstanding of the temporal revisitation. To our knowledge these studies are the first to order of Alt-Tab window switching. analyse real world revisitation in documents and to use the There are also several widely-deployed examples of results in the design, implementation, and evaluation of a automatic revisitation tools for navigating within read-wear scrollbar. documents. For example, the web browser’s ‘Back’ button works as normal when navigating through internal page RELATED WORK links, and Adobe Reader’s ‘Previous/Next View’ feature Revisitation and its support steps through a linear history of scroll positions and zoom Zipf’s Law [33], the Pareto Principle [22] and the “80-20 levels. Visual Studio also has a ‘previous/next’ list of lines Rule” all demonstrate that many facets of human behaviour that the I-beam cursor has visited. These history lists leave are highly repetitive: although we have extensive no visible trace in the scrollbar, however, so people cannot vocabularies, wardrobes, or choices at our disposal, most of visually scan potential target regions without displaying the time we reuse a small set of favoured options. additional windows or menus. Researchers have also demonstrated that many aspects of computer use are also highly repetitive, such as command Hill et al ’s [18] original Read Wear system showed a use [15, 16], menu selections [11, 14], and web page visits histogram overview of the reading history of an entire [2, 12, 29]. document within the scrollbar. Each horizontal line of pixels in the scrollbar encoded information such as the These observations have stimulated research into interface number of edits, or length of time reading. Similar scrollbar techniques for supporting reuse and revisitation. Some marks are used by several code editors, but the marks are strategies require manual intervention while others used to highlight semantic information such as compilation automatically observe actions and update the interface. errors rather than to support revisitation. Manual revisitation tools require an explicit user action to The concept of document read wear inspired several mark information as interesting. For example, bookmark researchers to examine a variety of techniques for recording tools in web browsers and Microsoft Word let people and visualizing activity beyond the scrollbar. These include explicitly create iconic labels as shortcuts for returning to Wexelblat and Maes’ [30] ‘Footprints’ system, which particular pages or positions in a document. The Bookmark provided maps, trails, annotations and signposts for Scrollbar [24]