design guidelines for effective www history mechanisms linda tauscher and saul greenberg university...
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Design Guidelines for Effective WWW History Mechanisms
Linda Tauscher and Saul GreenbergLinda Tauscher and Saul Greenberg
University of CalgaryUniversity of Calgary
This talk accompanied a paper, and was presented at:Tauscher, L. and Greenberg, S. (1996) Design Guidelines for Effective WWW History Mechanisms. In Microsoft Workshop, Designing for the Web: Empirical Studies. Microsoft Corporation, Redmond, WA. October 30
©Linda Tauscher & Saul Greenberg
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Overview
Introduction / ObjectivesIntroduction / Objectives Data CollectionData Collection ResultsResults Conditioning the DistributionConditioning the Distribution Design GuidelinesDesign Guidelines ConclusionConclusion
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Introduction
History mechanisms allow people to revisit History mechanisms allow people to revisit pages viewed previouslypages viewed previously
History mechanisms can mitigate impact of:History mechanisms can mitigate impact of: vast amounts and poor structure of informationvast amounts and poor structure of information resource useresource use cognitive and physical navigation burdenscognitive and physical navigation burdens
Current history mechanisms are based on Current history mechanisms are based on ad-hoc approachesad-hoc approaches
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Objectives
Understand people’s revisitation patterns Understand people’s revisitation patterns when navigating the WWWwhen navigating the WWW
Evaluate current approaches, validate Evaluate current approaches, validate successful solutions, suggest alternativessuccessful solutions, suggest alternatives
Provide guidelines for effective browser Provide guidelines for effective browser history designhistory design
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Data Collection
Xmosaic 2.6 modified to capture user’s Xmosaic 2.6 modified to capture user’s browsing activitybrowsing activity
Volunteer participants used browser for 6 Volunteer participants used browser for 6 weeksweeks
Participants were practiced Web usersParticipants were practiced Web users Quantitative data derived from logs of 23 Quantitative data derived from logs of 23
participantsparticipants Qualitative data gathered via interviewsQualitative data gathered via interviews
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Results
Recurrence of Web page visitsRecurrence of Web page visits Growth of URL vocabularyGrowth of URL vocabulary Web page visit frequency as a function of Web page visit frequency as a function of
distancedistance Frequency of URL accessesFrequency of URL accesses LocalityLocality Longest Repeated SequencesLongest Repeated Sequences
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Recurrence of Web page visits
Recurrence rate Recurrence rate RR probability that any URL visited is a repeat of a probability that any URL visited is a repeat of a
previous visitprevious visit University of Calgary: University of Calgary: RR = 58% ( = 58% ( = 9%) = 9%) Catledge and Pitkow: Catledge and Pitkow: RR = 61% ( = 61% ( = 9%) = 9%)
Web browsing is a Web browsing is a recurrent systemrecurrent system users predominately repeat activities invoked users predominately repeat activities invoked
before (Greenberg, 1993)before (Greenberg, 1993)
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Growth of URL vocabulary
URL vocabularyURL vocabulary number of unique URLs visited thus far vs. number of unique URLs visited thus far vs.
number of total URLs visitednumber of total URLs visited FindingsFindings
users incorporate new URLs into their users incorporate new URLs into their repertoire at a regular raterepertoire at a regular rate
revisits fairly evenly distributedrevisits fairly evenly distributed local variations highlight browsing patternslocal variations highlight browsing patterns
URL Vocabulary for participant 15
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Web page visit frequency as a function of distance Distance determined byDistance determined by
no. of items between current URL being visited no. of items between current URL being visited from its first match on the history listfrom its first match on the history list
Recency effectRecency effect previous 6 or so URLs contribute the majority previous 6 or so URLs contribute the majority
of pages visited nextof pages visited next
URL recurrence rate as a function of distance (all participants)
R as running sum
Frequency of URL visits for all participants
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Conditioning the Distribution
ObjectivesObjectives increase recurrence probabilities over a set of a given increase recurrence probabilities over a set of a given
sizesize evaluate methods currently in useevaluate methods currently in use
Method categoriesMethod categories recency ordered history listsrecency ordered history lists frequency ordered history listsfrequency ordered history lists stack-based approachesstack-based approaches hierarchically structured history listshierarchically structured history lists
Cumulative probabilities of recurrences over distances up to 50
RD10
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #1
Maintain records of URLs visited, and Maintain records of URLs visited, and allow users to recall previous URLs from allow users to recall previous URLs from those recordsthose records Web browsing is a recurrent system (Web browsing is a recurrent system (RR = 58%) = 58%) a history mechanism has valuea history mechanism has value
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #2
It should be cheaper, in terms of physical and It should be cheaper, in terms of physical and cognitive activity, for users to recall URLs cognitive activity, for users to recall URLs from a history mechanism than to navigate to from a history mechanism than to navigate to them via other methodsthem via other methods attempt to predict the next URL selectionattempt to predict the next URL selection clearly distinguish the best predictionsclearly distinguish the best predictions minimize the number of physical actions to retrieve minimize the number of physical actions to retrieve
URL from historyURL from history provide clues to Web space structureprovide clues to Web space structure
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #3
A selectable history list of the previous 10 A selectable history list of the previous 10 URLs visited provides a reasonable set of URLs visited provides a reasonable set of candidates for reusecandidates for reuse accounts for 43% of all Web pages visitedaccounts for 43% of all Web pages visited consider screen real estate, and cognitive consider screen real estate, and cognitive
overhead of scanning itemsoverhead of scanning items user able to predict if URL will be on the listuser able to predict if URL will be on the list
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #4
Other strategies for presenting the history Other strategies for presenting the history list, particularly pruning duplicates and list, particularly pruning duplicates and hierarchical structuring, increase the hierarchical structuring, increase the probability of it containing the next URLprobability of it containing the next URL 26% of recurring total are not covered by last 26% of recurring total are not covered by last
10 items10 items more difficult to recall and/or locate these more difficult to recall and/or locate these
URLsURLs
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #5
History based on recency is not effective for History based on recency is not effective for all possible recalls because it lists only a all possible recalls because it lists only a few previous events; alternative strategies few previous events; alternative strategies must be supportedmust be supported a few URLs are frequently visiteda few URLs are frequently visited
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #6
URLs already recalled through history URLs already recalled through history should be easily reselectableshould be easily reselectable implicit: recency methodimplicit: recency method explicit: highlight itemexplicit: highlight item
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #7
History items should have a meaningful History items should have a meaningful representationrepresentation URLs versus titlesURLs versus titles display lengthdisplay length
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #8
Support grouping of URLs into high-level Support grouping of URLs into high-level Web tasks, and switching between tasksWeb tasks, and switching between tasks context-sensitive Web subspacescontext-sensitive Web subspaces recency ordered hyperlink sublistsrecency ordered hyperlink sublists
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Design Guideline #9
Allow end-user customization of history Allow end-user customization of history datadata customize attributes of history itemscustomize attributes of history items save portions of browsing historysave portions of browsing history
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Conclusion
Empirical dataEmpirical data justifies need for browser history mechanismsjustifies need for browser history mechanisms provides foundation for design guidelinesprovides foundation for design guidelines
Current stack-based model can be improved Current stack-based model can be improved uponupon
Design Guidelines for Effective WWW History Mechanisms Linda Tauscher & Saul Greenberg
Future research
Evaluate cognitive and physical effort of Evaluate cognitive and physical effort of alternative history list methodsalternative history list methods
Access impact of different HTML and Access impact of different HTML and browser articfacts e.g. framesbrowser articfacts e.g. frames
Validate design principlesValidate design principles