Evaluating Web Accessibility For Specific Mobile Devices

Slide 1: Evaluating Web Accessibility for Specific Mobile Devices Markel Vigo, A. Aizpurua, M. Arrue and J. Abascal University of the Laboratory of HCI Basque Country for Special Needs International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 2: Introduction • 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 3: Mobile Web vs Web Accessibility Mobile Web Web accessibility Small display size causes Lack of context disorientates visually disorientation on the user impaired users Lack of pointing device forces users Screen reader users suffer to use keyboards. Navigation is slowed information overload: navigation bars down and menus. Typing is a tedious task due to low Users with motor disabilities face text input rate analogous problems Due to low bandwidth images tend to Not providing alternatives for visual not to be loaded content raises accessibility barriers Lack of colour support may cause Information conveyed with colour information loss causes problems to colour-blind users Lack of support causes information Assistive technologies tend to have loss problems with newer technologies Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 4: Guidelines • 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 5: Guidelines & Evaluation • Related work: there are several tools that evaluate web pages against mobileOK Basic tests TAW MWI EvalAccessMOBILE ready.mobi Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 6: Guidelines & Evaluation • 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 7: Guidelines & Evaluation • 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 8: Architecture: overview Mobile Device’s Device- Device- tailored brand name and model Tailored Report Evaluation • Source Code Retriever • Device Information Retriever • Evaluation Engine Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 9: Source Code Retriever • 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 WWW • The Source Code Retriever retrieves a web resource simulating the access of a determined device by manipulating the Source Code Retriever “user-agent” HTTP header XHTML file Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 10: Device Information Retriever • 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 UAPRof a CC/PP file is created Device Information Jena profiles Retriever WURLF API WURLF profiles • Both sources have complementary information CC/PP file Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 11: Extending mobileOK Basic tests • 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. Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 12: Guidelines Instantiator • 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 CC/PP mobileOK file tests • Once the guideline is completed XQUERY tests are dynamically created Guidelines Instantiator XQUERY tests Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 13: Guidelines Instantiator • Example for the IMAGE_MAPS test CC/PP excerpt <access:pntSupport>true</access:pntSupport> <test_case id="8"> UGL excerpt <evaluation_type>auto</evaluation_type> <evaluation_result>error</evaluation_result> <profile_feature type="access:pntSupport"/> <value> </value> true <element> <label>OBJECT</label> CC/PP mobileOK <test_elem>check attribute</test_elem> <related_attribute> file tests <atb>ismap</atb> </related_attribute> </element> </test_case> Guidelines Instantiator XQUERY let $tmp:=web_doc.xml//OBJECT[@ismap] return test if(not( true ))then for $i in $tmp return XQUERY <error>{$i/@line, $i/name()}</error> tests Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 14: Evaluation Engine • Once we have a set of XQUERY tests evaluation is straightforward using XSLT Device Jena UAPRof profiles Information processors Retriever WURLF API WURFL profiles • Summary: 2. Web resource is retrieved changing HTTP WWW CC/PP file mobileOK tests headers 3. Information regarding the device is Source Code Guidelines Instantiator retrieved from profile repositories and Retriever a CC/PP file is created XHTML XQUERY 4. Slots in guidelines specifications are filled file tests in with CC/PP data and XQUERY tests are automatically created Evaluation Engine 5. XHTML file is evaluated against the dynamically created queries and a device- Evaluation tailored report is obtained Report Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 15: Case Study • Nine web pages have been evaluated with 3 different mobile devices  D1: less support than the DDC  D2: similar to the DDC  D3: more features than the DDC mobileOK Basic Specific Evaluations for mobileOK Basic D1, D2, D3 D1 D2 D3 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 16: Case Study • 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 ↓ Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 17: Last remarks • 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/ Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 18: Conclusions & Future Work • 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 Introduction Guidelines Architecture Case Study Conclusions International Cross-Disciplinary Conference on Web Accessibility, W4A 2008

Slide 19: Evaluating Web Accessibility for Specific Mobile Devices Any question? Markel Vigo, A. Aizpurua, M. Arrue and J. Abascal University of the Laboratory of HCI Basque Country for Special Needs International Cross-Disciplinary Conference on Web Accessibility, W4A 2008