Evaluating Web Accessibility For Specific Mobile Devices
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Evaluating Web Accessibility For Specific Mobile Devices Presentation Transcript

  • 1. Evaluating Web Accessibility for Specific Mobile Devices Markel Vigo , A. Aizpurua, M. Arrue and J. Abascal Laboratory of HCI for Special Needs International Cross-Disciplinary Conference on Web Accessibility, W4A 2008 University of the Basque Country
  • 2. Introduction International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Generally, web content is developed with desktop computers in mind
      • Server-side services or proxies transform content
      • User Agents provide new features for better user experience: fast navigation mechanisms or content linearization
    • Mobile Web and Web Accessibility for physically impaired users share similar problems
    • Problems that able-bodied user may have are similar to those found by people with disabilities
    Guidelines Architecture Case Study Conclusions Introduction
  • 3. Mobile Web vs Web Accessibility International Cross-Disciplinary Conference on Web Accessibility, W4A 2008 Guidelines Architecture Case Study Conclusions Introduction Mobile Web Web accessibility Small display size causes disorientation on the user Lack of context disorientates visually impaired users Lack of pointing device forces users to use keyboards. Navigation is slowed down Screen reader users suffer information overload : navigation bars and menus. Typing is a tedious task due to low text input rate Users with motor disabilities face analogous problems Due to low bandwidth images tend to not to be loaded Not providing alternatives for visual content raises accessibility barriers Lack of colour support may cause information loss Information conveyed with colour causes problems to colour-blind users Lack of support causes information loss Assistive technologies tend to have problems with newer technologies
  • 4. Guidelines International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Mobile Web Best Practices MWBP 1.0 were released by the W3C
    • mobileOK test are techniques to conform with MWBP 1.0
      • mobileOK Basic: mobileOK Basic conformance  “functional user experience”
      • mobileOK Pro: techniques are to be released
    • Rely on the “Default Delivery Context”
    Usable screen width : 120px minimum Mark-up language support: XHTML Basic 1.1 Character-encoding: UTF-8 256 colours minimum CSS level 1 support Scripting is not supported Guidelines Architecture Case Study Conclusions Introduction
  • 5. Guidelines & Evaluation International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Related work: there are several tools that evaluate web pages against mobileOK Basic tests
    Guidelines Architecture Case Study Conclusions Introduction TAW MWI ready.mobi EvalAccess MOBILE
  • 6. Guidelines & Evaluation International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • mobileOK Basic test are intended for development purposes BUT
    • There are different flavours of mobile devices
    • These test produce problems when mobile devices deviate from DDC
      • Newer models  false positives
      • Legacy devices  false negatives
    Guidelines Architecture Case Study Conclusions Introduction
  • 7. Guidelines & Evaluation International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • MWBP 1.0 are full of statements regarding device features. E.g.: “ Do not use tables unless the device is known to support them ”
    • Objective: a tool that evaluates mobileOK Basic tests considering the specific features of mobile devices when required
    • mobileOK Basic test are extended, focusing on the device-dependent tests
    Guidelines Architecture Case Study Conclusions Introduction
  • 8. Architecture: overview International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Source Code Retriever
    • Device Information Retriever
    • Evaluation Engine
    Device-Tailored Evaluation Device-tailored Report Guidelines Architecture Case Study Conclusions Introduction Mobile Device’s brand name and model
  • 9. Source Code Retriever International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Objective: retrieve the source code in the same way that a mobile device would get it
    • Some web servers identify the ‘user-agent’ HTTP header and deliver different web content
    Source Code Retriever XHTML file WWW
    • The Source Code Retriever retrieves a web resource simulating the access of a determined device by manipulating the “user-agent” HTTP header
    Guidelines Architecture Case Study Conclusions Introduction
  • 10. Device Information Retriever International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Two ways to obtain information about a determined mobile device:
      • UAProf profiles  extended CC/PP profiles using prf namespace
      • WURFL (Wireless Universal Resource file)  XML file
    • Heterogeneous information sources
    • Required data are extracted and a CC/PP file is created
    • Both sources have complementary information
    Guidelines Architecture Case Study Conclusions Introduction CC/PP file Device Information Retriever Jena WURLF API WURLF profiles UAPRof profiles
  • 11. Extending mobileOK Basic tests International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • The implications that devices characteristics have on the mobileOK Basic tests have analyzed
    • New CC/PP based vocabulary has been created to express certain concepts
    • Examples
      • CONTENT_FORMAT_SUPPORT  access:picFormatSupport
      • NO_FRAMES  prf:FramesCapable
      • OBJECTS_OR_SCRIPTS  prf:JavaScriptEnabled
    • Information to be retrieved are the issues that the DDC captures: character encoding, image format support etc.
    Guidelines Architecture Case Study Conclusions Introduction
  • 12. Guidelines Instantiator International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • mobileOK Basic test are implemented using UGL (Uniform Guidelines Language)
      • It has slots so that values can be put in guidelines
    • Device data from the CC/PP file is used to fill in slots in the mobileOK test
    • Once the guideline is completed XQUERY tests are dynamically created
    XQUERY tests mobileOK tests CC/PP file Guidelines Instantiator Guidelines Architecture Case Study Conclusions Introduction
  • 13. Guidelines Instantiator International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Example for the IMAGE_MAPS test
    XQUERY tests mobileOK tests CC/PP file Guidelines Instantiator <access:pntSupport > true </access:pntSupport> <test_case id=&quot;8&quot;> <evaluation_type>auto</evaluation_type> <evaluation_result>error</evaluation_result> <profile_feature type=&quot; access:pntSupport &quot;/> <value> </value> <element> <label>OBJECT</label> <test_elem>check attribute</test_elem> <related_attribute> <atb>ismap</atb> </related_attribute> </element> </test_case> CC/PP excerpt UGL excerpt let $tmp:=web_doc.xml//OBJECT[@ismap] return if(not( ))then for $i in $tmp return <error>{$i/@line, $i/name()}</error> XQUERY test true true Guidelines Architecture Case Study Conclusions Introduction
  • 14. Evaluation Engine International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Summary:
    • Web resource is retrieved changing HTTP headers
    • Information regarding the device is retrieved from profile repositories and a CC/PP file is created
    • Slots in guidelines specifications are filled in with CC/PP data and XQUERY tests are automatically created
    • XHTML file is evaluated against the dynamically created queries and a device-tailored report is obtained
    Evaluation Engine Evaluation Report XQUERY tests mobileOK tests CC/PP file Device Information Retriever Guidelines Instantiator Jena WURLF API WURFL profiles UAPRof profiles
    • Once we have a set of XQUERY tests evaluation is straightforward using XSLT processors
    Guidelines Architecture Case Study Conclusions Introduction Source Code Retriever XHTML file WWW
  • 15. Case Study International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Nine web pages have been evaluated with 3 different mobile devices
      • D 1 : less support than the DDC
      • D 2 : similar to the DDC
      • D 3 : more features than the DDC
    Guidelines Architecture Case Study Conclusions Introduction mobileOK Basic Specific Evaluations for mobileOK Basic D 1 , D 2 , D 3 D 1 D 2 D 3 www.google.com 4 4 4 4 www.youtube.com 3 2 3 2 www.flickr.com 4 4 5 4 www.amazon.com 9 10 9 9 www.gmail.com 9 5 9 5 www.facebook.com 7 7 6 6 m.yahoo.com 6 6 6 6 m.twitter.com 8 6 8 6 www.wikipedia.org 428 363 358 280
  • 16. Case Study International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Looking carefully at results…
      • Mobile versions of traditional web pages have fewer errors with respect to desktop web pages
      • Devices with less support than the DDC tend to produce more errors  false negatives ↓
      • while those with better support and more characteristics yield fewer errors  false positives ↓
    Guidelines Architecture Case Study Conclusions Introduction
  • 17. Last remarks International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • The tool can be used for the development of accessible applications
    • Main purpose is to plug this tool in a more general framework
      • Goal: obtain user and device tailored accessibility scores as the user interacts
    • Demonstration of a prototype:
    • http://sipt07.si.ehu.es/mobile/
    Guidelines Architecture Case Study Conclusions Introduction
  • 18. Conclusions & Future Work International Cross-Disciplinary Conference on Web Accessibility, W4A 2008
    • Summary:
      • The presented tool deals with device specific accessibility issues
      • mobileOK Basic tests have been extended
      • False positives and false negatives diminish
    • Future Work
      • mobileOK Basic tests contain many references to HTTP headers content. Currently our approach deals with mark-up issues
      • mobileOK Pro are expected to be released
    Guidelines Architecture Case Study Conclusions Introduction
  • 19. Evaluating Web Accessibility for Specific Mobile Devices Markel Vigo , A. Aizpurua, M. Arrue and J. Abascal Laboratory of HCI for Special Needs International Cross-Disciplinary Conference on Web Accessibility, W4A 2008 University of the Basque Country Any question?