W4 A Sirithumgul

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  • Good evening, My name is Pornpat Sirithumgul. A student from Chulalongkorn university Thailand. Today I will present in the topic “Quantitative Evaluation for Web Accessibility with Respect to Disabled Groups”.
  • W4 A Sirithumgul

    1. 1. Quantitative Evaluation for Web Accessibility with Respect to Disabled Groups
    2. 2. Abstract <ul><li>The Web Accessibility Initiative (WAI) proposed Web Content Accessibility Guidelines (WCAG) in order to describe qualifications of accessible web pages. </li></ul><ul><li>The level conformance evaluation of WCAG (Levels A, AA and AAA) cannot indicate accessibility for specific disabled groups. </li></ul><ul><li>In this paper, we propose a methodology for evaluating web accessibility with respect to disabled users, especially the vision-impaired and the hearing-impaired. </li></ul>
    3. 3. Related Work (1) <ul><li>Automatic tools for qualitative evaluation such as ATRC, A-Prompt, </li></ul><ul><li>WAVE4.0, EvalAccess2.0 and Tidy </li></ul><ul><li>Quantitative Evaluation </li></ul><ul><ul><li>Sullivan et al., 2000 </li></ul></ul>
    4. 4. Related Work (2) <ul><li>Quantitative Evaluation </li></ul><ul><ul><li>Zeng et al., 2004 </li></ul></ul><ul><ul><li>Web Accessibility Benchmarking Cluster introduce UWEM 0.5 (Unified Web Evaluation Methodology 0.5), 2005 </li></ul></ul>
    5. 5. Related Work (3) <ul><li>Quantitative Evaluation </li></ul><ul><ul><li>Web Accessibility Benchmarking Cluster introduce UWEM 1.0 (Unified Web Evaluation Methodology 1.0), 2006 </li></ul></ul>
    6. 6. Related Work (4) <ul><li>Quantitative Evaluation </li></ul><ul><ul><li>Bühler et al., 2006 </li></ul></ul>where Nb is the number of potential barriers; Bb is the number of failures for one barrier type; B is the number of all failures.
    7. 7. Related Work (5) <ul><li>Brajnik et al., 2006 </li></ul><ul><ul><li>They propose the Barrier Walkthrough method (BW), adapted from the heuristic walkthrough method which is used for usability investigation. </li></ul></ul><ul><ul><li>A barrier is derived from the usage scenario of users. </li></ul></ul><ul><ul><li>In this work, each barrier is grouped by user category, and WCAG checkpoints are listed as its causes. </li></ul></ul><ul><ul><li>But severity evaluation for barriers in this method is depended upon the expertise of assessors </li></ul></ul>
    8. 8. An Improved Approach (1) <ul><li>We adopt the BW to find possible barriers of assessed web pages and further analyze severity from related checkpoints of the barriers , which is based on two assumptions </li></ul><ul><ul><li>The first assumption </li></ul></ul><ul><ul><li>The barriers which relate to several checkpoints should have severity values greater than those which relate to few checkpoints. </li></ul></ul><ul><ul><li>The second assumption </li></ul></ul><ul><ul><li>The barriers which relate to Priority 1 checkpoints should have severity values greater than those which relate to Priority 2 and Priority 3 checkpoints. </li></ul></ul>
    9. 9. An Improved Approach (2) <ul><li>Our approach has two stages </li></ul><ul><li>The first stage : </li></ul><ul><ul><li>We adopt the BW to find possible barriers of assessed web pages. </li></ul></ul><ul><ul><li>All barriers will be transformed into their related checkpoints for each disabled group. </li></ul></ul>
    10. 10. An Improved Approach (3) <ul><li>Our approach has two stages </li></ul><ul><ul><li>The second stage : </li></ul></ul><ul><ul><ul><li>All violated checkpoints will be calculated to find severity value from our formula, T1 </li></ul></ul></ul><ul><ul><ul><li>Our formula is derived from WAB_SCORE </li></ul></ul></ul>
    11. 11. An Improved Approach (4) where is number of potential barrier types on a web page is number of actual barriers for barrier type i is number of potential barriers for barrier type i is number of checkpoints related to priority level p and barrier type i.
    12. 12. An Improved Approach (5) <ul><li>In addition, the result of the formula is normalized in the range of [0, 1] by tuning weight used in the calculation. </li></ul><ul><li>By following WAB_SCORE, Priority 1 is twice as important as Priority 2 and three times as important as Priority 3 (W2 = W1/2 and W3 = W1/3) </li></ul><ul><li>W1 + W2+ W3 = 1 </li></ul><ul><li> W1 +(1/2) W1+ (1/3)W1 = 1 </li></ul><ul><li>Therefore W1= 6/11; W2= 3/11 and W3= 2/11 </li></ul>
    13. 13. Experiment <ul><li>In our experiment, we used web pages on &quot;.com&quot;, &quot;.gov&quot; and &quot;.edu&quot; domains. </li></ul><ul><li>All pages had &quot;Level A conformance icon&quot; WAI logos on the pages. </li></ul><ul><li>To acquire these pages, we used “Level A conformance icon, W3C-WAI Web Content Accessibility Guidelines 1.0” as search keywords using the Google search </li></ul>
    14. 14. Model Evaluation Comparison of values from T1 and A3 from all data
    15. 15. Results and Discussion <ul><li>The pages which comply with Level A satisfy only 11 checkpoints out of 37 for the vision-impaired. </li></ul><ul><li>They omit 26 checkpoints of Level AA and Level AAA, which may be the cause of 15 types of possible barriers for that group. </li></ul><ul><li>From the experimental results, although all pages claim they conform to LevelA, </li></ul><ul><li>only 64.41% of those actually conform when re-checked by EvalAccess 2.0, while 19.46% of these are suitable for the vision-impaired. </li></ul>
    16. 16. Conclusion <ul><li>Our evaluation methodology can help complement the level conformance evaluation offered by WCAG. </li></ul><ul><li>From our study, we found that Level A conformance pages may be not suitable for some groups of users such as the vision-impaired </li></ul><ul><li>Violated checkpoints are computed to be a single value representing the accessibility of a web page. </li></ul><ul><li>The correlation of results from our formula, T1 and baseline, A3 is rather strong. </li></ul><ul><li>The strong correlation shows quality of our approach that it can indicate accessibility for the specific disabled group. </li></ul>

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