Evaluating Web Accessibility For Specific Mobile Devices

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

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

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

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

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

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

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

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

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

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

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 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

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="8"> <evaluation_type>auto</evaluation_type> <evaluation_result>error</evaluation_result> <profile_feature type=" access:pntSupport "/> <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

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

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

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 ↓

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/

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

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?

Evaluating Web Accessibility For Specific Mobile Devices

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