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W4 A Sirithumgul
 

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 W4 A Sirithumgul Presentation Transcript

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