APRIL 13-18, 1996 CHI 96
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`The WebBook and the Web Forager:
`An Information Workspace for the World .. Wide Web
`
`Stuart K. Card, George G. Robertson, and William York
`Xerox Palo Alto Research Center
`3333 Coyote Hill Road
`Palo Alto, California 94304
`E-mail: {card I robertson I york} @parc.xerox.com
`
`ABSTRACT
`The World-Wide Web has achieved global connectivity
`stimulating the transition of computers from knowledge
`processors to knowledge sources. But the Web and its
`client software are seriously deficient for supporting users'
`interactive use of this information. This paper presents two
`related designs with which to evolve the Web and its
`clients. The first is the WebBook. a 3D interactive book of
`HTML pages. The WebBook allows rapid interaction with
`objects at a higher level of aggregation than pages. The
`second is the Web Forager. an application that embeds the
`WebBook and other objects in a hierarchical 3D
`workspace. Both designs are intended as exercises to play
`off against analytical studies of information workspaces.
`
`Keywords
`3D graphics. user interfaces. information access. World(cid:173)
`Wide Web. information workspace, workspace.
`
`INTRODUCTION
`Whereas personal computers used to be viewed as
`knowledge processors-word processors or spreadsheet
`calculators. for instance. they are now becoming viewed as
`knowledge sources-portals to vast stores of information
`on-line or on CD-ROMs [I]. This is true because much
`work has become knowledge work and because the
`infrastructure for distributed knowledge access has been
`developing. The most dramatic development of this
`infrastructure has been the growth of the World Wide Web
`in the last couple of years. Uniform access protocols have
`enabled a person with a personal computer and a
`communications link access by button-click to millions of
`pages around the world.
`
`Despite the exhilaration felt by many users at this
`achievement of wide-scale connectivity. there are problems
`that call for evolution of the medium: Pages are often hard
`to find. users get lost and have difficulty relocating
`previously-found pages. they have difficulty organizing
`thincrs once found. difficulty doing knowledge processing
`0
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`on the found thing. and interacting with the Web IS
`
`Permission to make digital/hard copies of all or part of this material for
`personal or classroom use is granted without fee provided that the copies
`are not made or distributed for profit or commercial advantage, the copy(cid:173)
`ri.ght notice, the title of the publication and its date appear, and notice is.
`g1ven that copyright is by permission of the ACM, Inc. To copy otherwise,
`to republish, to post on servers or to redistribute to lists, requires specific
`permission and/or fee.
`CHI96 Vancouver, BC Canada
`e 1996 ACM 0-89791-777-4/96/04 .. $3.50
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`notoriously too slow to incorporate it gracefully into human
`activity. In this paper. we suggest a way of viewing the
`Web and its problems. then propose two related
`innovations. the WebBook and the Web Forager. to
`mitigate these problems.
`
`INFORMATION FORAGING ON THE WEB
`In an information-rich world. the limiting quantity for users
`isn't so much the information in the world as the user's
`own limited time. Just as animals forage for food and try to
`optimize their food rate of gain. users often seek strategies
`to optimize their information gain per unit time and in fact.
`we can make the analogy literal by thinking of the Web in
`terms of Information Foraging Theory [1], an analogue of
`foraging models from ecological biology [2].
`
`In terms of this theory. the user stalks certain types of
`information.
`In a particular environment. this sort of
`information is encountered at a certain rate of A relevant
`pages/hour. say. The Web is an evolving information
`ecology in which on the one hand users are trying to evolve
`methods to increase the encounter rates of relevant
`information and on the other hand information sources are
`trying to evolve their attractiveness to users. These result
`in a clumpy structure of patches of high A. Three
`mechanisms in particular have evolved on the server side:
`First. indexes. such as Lycos [3] attempt to visit and form
`an inverted index of every page by following all the links.
`The user can formulate a keyword query and obtain a patch
`of possible links to forage. Creation of such a patch is a
`form of information enrichment.
`
`A second sort of information enrichment is a table of
`contents lists such as Yahoo [ 4]. These systems provide
`typically a tree of categories with links of Web pages at
`their leaves. Again. this technique provides enriched
`patches for foraging. A third sort of enrichment are the
`home pages provided by many users. which collect together
`lists of related links. Again. these often provide patches
`with higher encounter rates. All three responses represent
`evolutionary adaptation (Lycos and Yahoo are successful
`enough that they have now been converted to businesses)
`and emergent self-organizing structure on the Web. Yet
`these innovations do not address the basic cost-structure
`problem of users using Web information as part of some
`activity.
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`THE COST STRUCTURE OF INFORMATION
`WORKSPACES
`The Web maintains a uniform cost structure. The time per
`interaction is fast. compared to the time to. say. go to the
`library. but it is slow compared to interaction rates. say the
`time
`to
`interact with pieces of paper on a desk.
`Empirically . users tend to interact repeatedly with small
`clusters of infonnation. a property known as locality of
`reference [5. 6]. As a result. information workspaces. that
`is. environments that are cost-tuned for doing information(cid:173)
`based work. tend to exhibit a certain cost-structure of
`infonnation: a small amount of infom1ation is organized to
`be available at very low cost. larger amounts are available
`at moderate costs. large amounts at high cost. By so doing.
`they capitalize on locality of reference and the activity is
`speeded considerably. A routine example would be a
`typical (ideal) office where a small amount of infom1ation
`is kept available on the desk; moderate amounts of
`information. moderately available in nearby files: and large
`amounts. slowly available are kept in a library down the
`hall. Users constantly rearrange their environments to tune
`the relative costs of the information. so as to make them
`efficient. And if they don't. they suffer accordingly. An
`important activity they do in such environments is to use
`them for sensemaking [7]. that is. the restructuring.
`recoding. and analysis of information for purposes of
`insight.
`
`But the Web does not exhibit the characteristics of a good
`information workspace. Users do not have the ability to
`create adequately tuned environments nor is sensemaking
`supported. The major effort to allow users to organize their
`workspaces has been the development of variants of the
`"hotlist" notion. Fig. 1 show a typical example from
`Netscape l.lN. User actions are provided for adding or
`deleting an element to a hot list. arranging an element under
`a heading. changing it's position in the list. or searching for
`it. Because of the interface. these mechanisms are very
`slow to use and do not work well with more than a couple
`dozen entries. Even when the entry is found. the user must
`still wait for the slow access times before the page appears.
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`CHI 9 6 AP RI L 13-18. 1 9 9 6
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`Hence the space is not tunable to a reasonably cost(cid:173)
`structured workspace. Multiple windows can be spawned
`for access to multiple pages. but these then slow the user
`down because they overlap. F inally. sen semaking is
`impeded.
`In the conventional Web browsers. users are
`always uta particular page. But the way a user works with
`information is to have multiple pages simultaneously
`available that can be juxtaposed. rapidly accessed. and
`structured. such as by grouping or other layout.
`
`In order to make the use of the Web bette r able to support
`information work (or for that matter. entertainment). we
`propose in this paper two basic moves:
`
`(I) A move from the single Web page as the unit of
`interaction to a higher. aggregate entity.
`
`We call this entity a WebBook™. and it allows the user to
`group together related Web pages (an elementary form of
`sensemaking) and to manipulate these pages as a unit.
`
`(2) A move from a work environment containing a
`single element to a workspace in which the page is
`contained with multiple other entities. including
`WebBooks.
`We call this environment the Web Forager ™. This
`information workspace allows for the intensive. rapid
`interaction among pages and allows for the assembly on the
`user side of hierarchical cost-structures of information
`necessary for the task tuning of the workspace.
`
`Each of these has been implemented on a Silicon Graphics
`Iris computer using the Information Visualizer system [8].
`Efforts are underway to reimplement them on a PC and to
`continue advancing the design.
`
`THEWEBBOOK
`Current Web servers and browsers focus attention at the
`link and page levels. These levels are too low to represent
`gracefully some higher-level structures. resulting in many
`more entities in the Web space than are necessary and
`
`Fig. l. Hotlist browser from Netscape.
`
`Fig. 2: Example of a WebBook (See Color Plate 2).
`
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`hence to orientation and sensemaking problems. We know
`from analysis of the web that there are structures that the
`user could take advantage of if the user were aware of their
`existence. For example. a typical home page on the web
`has a collection of related pages that can be reached with
`relative URLs (Uniform Resource Locators). It is very
`typical for the creator of such pages to use relative URLs
`instead of absolute URLs. so that the collection of pages
`can be physically moved easily. But current web browsers
`pay no attention to the distinction between relative and
`absolute URLs. and the user simply sees one page at a time.
`with no difference between a page "in the collection" and
`one outside the collection. Our proposal is to create a Web
`entity at a higher level of abstraction. a WebBook. A
`natural candidate structure to represent this abstraction is
`the book metaphor. which has been used by us [9] as well
`as others [ l0-18] previously.
`
`Fig. 2 shows a picture of a WebBook. Given a collection of
`web pages. it preloads those pages and displays them as a
`collection using an augmented simulation of a physical
`book. 3D graphics and interactive animation are used to
`give the user a clear indication of the relationsbp between
`the pages of the book. Each page of the WebBook is a page
`from the web. Links are color coded so the user can easily
`tell the difference between a reference to another page in
`the book (red links) and a reference outside the book (blue
`links). Picking a red link will animate the flipping of pages
`to the desired page. Picking a blue link will close the
`current WebBook and look for the page elsewhere. If the
`page is in another WebBook stored on a bookshelf. that
`WebBook is opened to the desired page. If the page is in
`none of the WebBooks. then the Web Forager is used to
`display the individual page in the user's information
`workspace.
`
`There are a number of features in the WebBook that make
`it intuitive to use. The user has several ways to flip through
`the pages of the book. all animated so the user can continue
`to see the text and images on pages while they tum. The
`simplest method is to click on a page (away from any link
`on that page); this will flip to the next or previous page
`
`Fig. 3. Example of ruffling pages in a WebBook (See Color
`Plate 3)
`
`depending on whether user clicked on the right or left page.
`The user can also click on the right or left edge of the book.
`The relative distance along that edge indicates how far to
`flip. The user can also scan the book with forward and
`backward scan controls (two of the buttons on the bottom
`of the book). The scan rate and pause time at each page is a
`user preference. When the user clicks on a page during a
`scan. the scan stops. Finally. the user can ruffle through the
`pages (Fig. 3) by clicking and holding the mouse button
`down. The ability to rapidly riffle through a set of pages
`has previously been a method of rapid scanning for
`information that could only be done with physical books.
`
`In addition. the user can leave a bookmark on any page.
`When the book is closed. a bookmark is automatically left
`for the last page that was viewed. Also. there is a "Back"
`and "History" mechanism that follows the same convention
`as NetScape's versions of those commands. The WebBook
`can be stored on a bookshelf using a simple gesture. When
`it is removed from the bookshelf (by clicking on it). it
`reopens to the last page that was being viewed.
`
`Each page in the WebBook has three scrollbars. Two of
`these are the familiar vertical and horizontal scrolling
`controls (left and bottom scrollbars). The third (on the
`right) is for scaling the font size. since the trade-off of font(cid:173)
`size vs. amount of page viewed differs for individual pages.
`As the scale scrollbar is moved. images remain the same
`size but the text changes size and is refilled continuously.
`A menu command allows the user to apply a new font scale
`to all pages of the WebBook. The comers of each page of
`the WebBook are resize tabs. which the user can use to
`change the size of the book.
`
`Books are compact but (except for bookmarks) sequential.
`Therefore we allow the user to explode the book out (in
`animation) so
`that all
`the pages are available
`simultaneously. The Document Lens [19] can then be used
`to inspect portions of interest. Fig. 4 shows the WebBook
`Document Lens view. The user is then able to pan and
`zoom over the entire set of pages. while retaining a focus
`plus context display of the book. When returning to the
`book view. the user sees an animation of the pages
`imploding into a book.
`
`WebBook Applications
`The WebBook can be used to view any collection of web
`pages. The principle difference is the method used to
`generate the URLs. The method used to collect URLs leads
`to a number of applications.
`
`Relative-URL Books. One interesting choice of pages is
`based on recursively finding all relative URLs starting from
`a given page. These pages are intrinsically related because
`their creator wanted to be able to move them as a group.
`We have found this heuristic often produces coherent and
`interesting books.
`
`Home-Page Books. Probably the simplest choice of pages
`is those pages referred to directly from a given page. Users
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`3D boo k. used to show coll ections of web pages. with an
`informa ti on workspace ma nager (the We b Forager) and the
`applicati on to Web problems.
`
`A book metaphor was chosen after careful examination of a
`large number of web pages an d page collections. and for
`several reasons: Informally. information on the Web tends
`to have non-homo geneous character. with closely re lated
`weblets situated in more loosely stmctured environments.
`An important subset of these have 'next' and 'prev ious'
`lin ks. and thu s are thu s close operational analogues to
`books. Furthermore, books as an in vention make very
`efficient use of di spla y space . Starting with a book
`metaphor, it is easy to escape the serial nature of the
`physical form by having alternate forms into which the
`book is transformed. such as the Document Lens in this
`paper. A book metaphor makes it easy to put actual books
`on the Internet. something not so at present. We use the
`book metaphor not primarily because it is famil iar. but
`because of the operational match to a corpus of interest and
`the efficient display characterization. As a bargain. its
`familiarity allows us to exploit irre sistible affordances for
`low training costs.
`
`Earl y experiments with gi ving users access to books. like
`Brown's Intermedia [ 10] system in 1985, had limited 3D
`graphics capabilities. Instead of a simulation of a physical
`book. Intermedia used 2D layouts of the pages, showing
`relationships between pages with the layout and with lines
`drawn between pages.
`In 1987. Card and Henderson
`reported the use of a 2D book simulation called
`"Catalogues" as part of the Rooms system [9], although
`page turning was not animated. The Xerox TabWorks
`system [ 16] was directly inspired by Catalogues. Also in
`1987. the BellCore SuperBook Document Browser [13].
`was designed to transform existing electronic documents
`into hypertext documents with indexing and a fisheye table
`of contents. although SuperBook did not use a simulation
`of a physical book.
`
`Use of a 2D physical book simulation, including page
`turning. was done in 1987 by Benest [17] for hypertext
`documents. Similar systems were reported by Miyazawa in
`1990 [11] and lchimura in 1993 [18] . Recently. PenPoint
`[14] and General Magic [15] have offered commercial
`products that use a book metaphor with bookshelves.
`These are actually 2D animations painted on a background
`that give the impression of a 3D environment. In 1993.
`Silicon Graphics introduced the SGI Demo Book [12] as a
`way of distributing collections of applications. documents.
`and games. Demo Book is a 3D book that simulates page
`flipping with animation. The pages hold a collection of
`icons, 4 rows by 5 columns on each page. The page
`flipping appears to have flexible pages (broken on the
`columns). The WebBook page flip currently uses rigid
`pages, but is displaying text and images instead of rows and
`columns of icons. Demo Book also has the notion of a
`bookshelf. although the book always opens to the first page
`rather than the last page viewed.
`
`throughout the net have strongly ex pressed their des ire to
`make sense of the net by collecting sets of rel ated URLs.
`The WebBook goes the nex t step and allows the coll ecti on
`of pages to be rapidl y cons ulted without wa itin g for
`network delay speeds.
`
`Fig. 4. WebBook viewed with a Document Lens.
`(See Color Plate 4)
`
`Topic Books. A variant is to make sets of books on
`interesting topics. For example. in our area houses for sale
`are published on the Web. usually one page per house and
`usually organized off the home pages of the real-estate
`brokers . But we have rearranged these ads into houses
`from a given city. It is then possible rapidly to look back
`an forth in order to make hou se comparisons.
`
`Hot List Books. Another variant is hotlist pages. Our
`sys tem can read an y user's Netscape hotli st and
`automatically fashion it into a set of WebBooks. Although
`exactly the same URLs are in volved. the transformation is
`dramatic because all the information on all the pages is
`readily available.
`
`Since WebBooks can be created
`Search Reports.
`dynamically. they can be used to display the results of a
`content based search. either keyword based or relevance
`feedback (looking for pages similar to a given page). Later
`results from the search can still be retrieving pages while
`the user is examining the first pages of the book.
`
`Book Books. A final example comes from observing how
`some people take multi-page documents and put them on
`the web. One way to do this is with a series of pages. with
`next and previous links between pages. When viewing one
`of these pages with a traditional web browser. there is no
`indication of how the pages are related. But. such a
`structure can be easily di scovered. and a WebBook
`constructed from those pages, resulting in a collection of
`obviously related pages.
`
`":elated Work: The Book Metaphor
`The book metaphor has been used in both 2D and 3D
`applications by a number of people for some time. What is
`new about the WebBook is the integration of an animated
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`Fig. 5: The Web Forager. (See Color Plate I)
`
`In 1995. Brown described an experimental web browser,
`called DeckScape [20], that used a metaphor of decks of
`cards. Although not a book metaphor. it was an alternative
`way to solve the problem.
`
`Web pages entered into the space are stored locally and
`thence forward are available at user interface speeds
`(around 1-0.1 sec). permitting high interaction rates. These
`pages can also be grabbed and placed intoWebBooks.
`
`All these systems exploit the human perceptual and
`cognitive systems by using familiar objects. images and
`affordances . The page turning of a book conveys
`information about the relationship of pages. the direction
`you are moving in the book. the size of the book. and the
`contents of the book. The WebBook takes advantage of
`advances in graphics and processor power to get much
`closer to a realistic simulation of a book. At the same time.
`it goes beyond what is possible with a physical book.
`
`THE WEB FORAGER
`The WebBook provides a representation of a more
`aggregate Web entity above the page and allows rapid local
`interaction with it. The Web Forager allows interaction
`with multiples of such entities and allows for the necessary
`tradeoffs among fast access. number of entities. and screen
`space. The Web Forager is a proposal for a task-tunable
`information workspace [21] (see Fig. 5).
`
`An individual Web page or a WebBook is presented in a
`3D document space (see[22]. [23]). Users can click on
`links in the usual way causing the new linked-to page to fly
`into the space. The HTML image on the new page
`develops at the slow Internet speeds (often 15-30 sec).
`
`Our primary interest in this style of workspace is in
`exploring the potential for rapid interaction with large
`numbers of pages. We have previously explored the use of
`animation. scaling. and 3D-based distortions for building a
`workspace [21] as a way of handling large numbers of
`objects. Ark Interface. Inc. [24] produced a pseudo-3D
`workspace in which functions were associated with parts. of
`a picture of a design studio. Staples [23] did a design
`mockup study for a 3D user interface. Her goal was to
`enrich the graphic vocabulary of the workspace by applying
`perspective. light. and transparency. Ballay [22] with co(cid:173)
`workers at the MAY A Design Group implemented a 3D
`design for an office system. Their design is artistically
`striking and claimed to be able to handle hundreds of
`documents. We have sought to break new ground relative
`to their design on several fronts. First. we tried to increase
`the speed with which objects can be moved around the
`space by using gestures. Second, we focused on the Web.
`Third, the WebBook provides a higher-level object.
`Fourth, we have experimented with observer movement in
`the space. And Fifth, we have used a structured model for
`the generation of the design.
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`Hierarchical Workspace
`The Web Forager workspace (see Fig. 5) is arranged
`hierarchically (in tenns of interaction rates) into three main
`levels: ( 1) a Focus Place (the large book or page) showing
`a page. a book. or an open book at full size for direct
`interaction between user and content; (2) an Immediate
`Memory space (the air and the desk). where pages or books
`can be placed when they are in use. but not the immediate
`focus (like pages on a desk). A Tertiary Place (the
`bookcase) where many pages and books can be stored.
`
`The Immediate Storage place has several tiers. Documents
`are arranged at several distinct z-distances in the 3D space.
`The user can move these documents back in space (the
`farther back. the smaller they become and the more
`documents that fit). Objects in the Immediate Storage place
`can be moved around in X and Y and moved forward and
`backward (that is. in Z) using a simple gesture language. A
`separate Intermediate Storage area is represented by objects
`on the desk. When the user moves around in the space. the
`desk. and hence objects on the desk. moves.
`
`The Tertiary Storage area is the bookcase. In normal view.
`the bookcase is seen at an angle to reduce screen pixels
`consumed. while at the same time displaying enough
`information that recently-used books can be recognized. If
`the user touches one of the books or pages in the bookcase.
`it will t1y up to the focus area (an object occupying that
`area will automatically fly back to an Immediate Storage
`position). But if the user wants to examine better the books
`before making a choice. then touching the bookcase will
`cause the user. desk and all. to fly to the bookcase (Fig. 6).
`Touching a book will then cause the user to fly back to the
`home position and the book to fly to the focus position.
`
`Fig. 6: User has flown to the bookcase where the titles of the
`books can be easily read. (See Color Plate 5)
`
`5
`
`10
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`1 5
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`20
`
`Time to Access (s)
`
`Fig. 7. Preliminary computation of Cost of Knowledge
`Characteristic Function for Web Forager.
`
`Storage workspace can hold about 30 documents without
`occlusion. and over a hundred if occlusions are allowed
`(not counting book contents). Pages for ongoing activities
`· migrate into the rapid access and manipulation region. In
`this way. repeated reference due to locality of reference
`statistics can result in faster interaction.
`
`Cost of Knowledge Characteristic Function
`In previous work [25]. we have attempted to measure the
`access properties of a workspace by computing the Cost of
`Knowledge Characteristic Function, that is. a plot of how
`many objects can be accessed as a function of the time cost
`of accessing them. We surmise that a balanced workspace
`will exhibit an exponential relationship. most conveniently
`displayed as a straight line in semi-log coordinates. As a
`tool to use in refining our design. we have computed a
`preliminary version of this function. The computation
`assumes that there is a page in the Focus Position (hence
`the maximal occlusion). that the desk is full. and that one
`row of pages from each of the discrete Z-distances in the
`space shows (remember. the design of the space has been
`carefully set up to permit this).
`
`The results are shown in Fig. 7. They are roughly in the
`expected relation, except that the images on the desk permit
`the fast part of the space to receive extra loading. An
`illustrative comparison with a conventional Web browser is
`shown as a gray line assuming a constant 18 sec per page
`retrieval. We hope to use this and related techniques to
`further refine the space in future research.
`
`The purpose of the workspace is to allow a number of
`objects to be displayed together (mitigating the limitations
`of the small screen space) in order to support information(cid:173)
`intensive activities. The workspace sets up explicitly the
`capacity for speed/access-time tradeoff to allow tuning for
`such activities. The design aims to provide very rapid
`access to a small number of pages. smoothly integrated
`with the slower access to a large number. The Immediate
`
`SUMMARY
`The Web Forager workspace is intended to create patches
`from the Web where a high density of relevant pages can be
`combined with rapid access. In addition to multiple pages
`occurring simultaneously. the space contains groups of
`pages in the form of WebBooks. which can allow the user
`to express an elementary form of sensemaking by grouping
`and ordering. High density patches found around the net.
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`whether created explicitly by searchers or discovered
`through Web analysis methods can be put into a form
`where they can be rapidly interacted with. Through the
`invention of such techniques and analytical methods to help
`us understand them. it is hoped that the connectivity of the
`Web. which has been so successful. can be evolved into yet
`more useful forms.
`
`REFERENCES
`l. Pirolli. P. and S. Card. Inj(Jrmation Foraging in
`Information Access Environments, in CHI '95, ACM
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