Link annotation with the accessibility level of the target Web page is an adaptive navigation support technique aimed at increasing blind users’ orientation in Web sites. In this work, the accessibility level of a page is measured by exploiting data from evaluation reports produced by two automatic assessment tools. These tools support evaluation of accessibility and usability guideline-sets. As a result, links are annotated with a score that indicates the conformance of the target Web page to blind user accessibility and usability guidelines. A user test with 16 users was conducted in order to observe the strategies they followed when links were annotated with these scores. With annotated links, the navigation paradigm changed from sequential to browsing randomly through the subset of those links with high scores. Even if there was not a general agreement on the correspondence between scores and user perception of accessibility, users found annotations helpful when browsing through links related to a given topic.
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Enriching Web Information Scent for Blind Users
1. Enriching Web Information Scent for Blind Users Markel Vigo1, Barbara Leporini2, and Fabio Paternò2 1 Laboratory of HCI for Special Needs 2 Human Interfaces in Information Systems 1 University of the Basque Country 2 Italian National Research Council
2. Hypothesis: annotating links with the accessibility level of the page where they point would increase user orientation “Visually impaired users need to be warned of obstacles because their reliance on cues is higher than for sighted users”- Goble et al. ”Detecting and notifying users about barriers improves user orientation”- Harper et al. Goal: use of accessibility assessment results in web navigation scenarios Information Scent: Thus, we aim at enriching information scent using accessibility assessment results for screen reader users. 1. Introduction 1. Visual or textual cues provided on a Web site to suggest what information its links may contain. 2. The perceived usefulness of a page based on such information. Enriching Web Information Scent for Blind Users ACM ASSETS2009
3. Hypothesis: annotating links with the accessibility level of the page that the link point to increases user orientation “Visually impaired users need to be warned of obstacles because their reliance on cues is higher than for sighted users”- Goble et al. ”Detecting and notifying users about barriers improves user orientation”- Harper et al. Goal: deployment of accessibility assessment results in navigation scenarios Information Scent: Thus, we aim at enriching information scent using accessibility assessment results 1. Introduction not accessible highly accessible 1. Visual or textual cues provided on a Web site to suggest what information it or its links may contain. 2. The perceived usefulness of a page based on such information. fairly accessible Enriching Web Information Scent for Blind Users ACM ASSETS2009
9. Magenta checks adequate content of tags and attributes, arrangement of headings or shortcutsEnriching Web Information Scent for Blind Users ACM ASSETS2009
18. semi-automatic issues (earl:semiAuto)Enriching Web Information Scent for Blind Users ACM ASSETS2009
19. 3. User-Tailored Assessment: Measurement Traditional aggregation: where W: weights and E: evaluation results Logic Scores Preferences: where ρ(d) are values selected upon the required logical relationship between evaluation results. d=0 conjunction 0< d <0.5 quasiconjunction: simultaneity in satisfying all the evaluations d=0.5 arithmetic mean 0.5< d <1 quasidisjunction: penalizes only when all evaluations are not satisfied d=1 disjunction Only intermediate values are applied Enriching Web Information Scent for Blind Users ACM ASSETS2009
20.
21. between guidelines, mean valuefinal score ? guidelines 0.25 checkpoints test cases T2 T3 T1 1 0.25 0 Enriching Web Information Scent for Blind Users ACM ASSETS2009
34. Following a pattern: wikipedia, local university, soccer team and so on
35. One site was manually annotated with accessibility scores and relevance scores
36. Relevance based on ranking {very relevant, relevant, medium, low, irrelevant}- 5 min free browsing. They had to write a report about what they learned Enriching Web Information Scent for Blind Users ACM ASSETS2009
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38. 9 users proceeded sequentially. Kendall τ=[0.8-1.0] at most p<0.03
44. However, when aggregating accessibility scores of visited pages, 7 points over the median are obtained
45. This, can be interpreted as if the users browsed within the subset of more accessible pages according to random/preference criteriaEnriching Web Information Scent for Blind Users ACM ASSETS2009
59. Only 2 users proceeded sequentially. Kendall τ=1.0 at most p<0.05
60. One user followed the most accessible path. Kendal τ=1.0 at most p<0.02
61. Again, when aggregating accessibility scores of visited pages 6 points over the median are obtainedEnriching Web Information Scent for Blind Users ACM ASSETS2009
80. Considering the informal comments it seems that the annotation technique prevails over scoresEnriching Web Information Scent for Blind Users ACM ASSETS2009
81.
82. In the browsing scenario users change paradigm
83. From sequential browsing to random in the subset of most accessible links
85. When directly enquired, users state that accessibility annotations would be useful in those scenarios where the topic of the linked pages would be similarEnriching Web Information Scent for Blind Users
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87. Enriching Web Information Scent for Blind Users Questions? Markel Vigo1, Barbara Leporini2, and Fabio Paternò2 1 Laboratory of HCI for Special Needs 2 Human Interfaces in Information Systems 1 University of the Basque Country 2 Italian National Research Council
Hinweis der Redaktion
or added values
assumptions: all checkpoints, test cases have the same impact on the user
ACC: tags: summary for tables, attributes: alt for images and combination: formssome studies on: even if web pages are accessible they are not usableUSA: “click here” statements, shortcuts to skip to main content
there’s certainly an overlap
atomic rulesrecommendations: highly subjective issues, AT dependant issues. Violating them does not have a strong effect on accessibility but maybe on usability
LSP overcomes traditional aggregation methodstrong, medium, weakρ(d) values are obtained elsewhere –rho-INTUITIVE AND EXPLICIT WAY
Example to illustrate how it worksAll test cases have to be satisfied to meet the whole checkpointHowever the uncertainty on semi-automatic issues leads us to consider the medium quasidisjunctionamong earl:semi-automaticBetween checkpoints there also a sense of simultaneity to satisfy the whole guideline
capture ofget their impressions, free to comment .subjective data
as expected by blind users
why relevance was not considered: in this scenario it would lead to the solution
as expected by blind users
Even if they were not told to, in the after task forms users gave their opinion.changed their minds those that did first the task with annotated links in the first scenario. it was curious. surprisinglyTECHNIQUE PREVAILS OVER THE SCORES
At first sightEven if there’s a peak for mid values there’s not a general agreementUsefulness and perception of score validity is higher for the browsing task, at least it is more balanced
results are inconclusiveand how some user changed their minds about scores