Evaluating Web Accessibility For Specific Mobile Devices

Evaluating Web Evaluating Web Accessibility for Specific Accessibility for Specific Mobile DevicesMobile 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

IntroductionIntroduction


• 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 ConclusionsIntroduction

Mobile Web vs Web AccessibilityMobile Web vs Web Accessibility


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


GuidelinesGuidelines


• 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 minimumMark-up language support: XHTML Basic 1.1Character-encoding: UTF-8256 colours minimumCSS level 1 supportScripting is not supported


Guidelines & EvaluationGuidelines & Evaluation


• Related work: there are several tools that evaluate web pages against mobileOK Basic tests


TAWTAW MWIMWI

ready.mobiready.mobiEvalAccessMOBILEEvalAccessMOBILE



• 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: overviewArchitecture: overview


• Source Code Retriever

• Device Information Retriever

• Evaluation Engine

Device-Tailored

Evaluation

Device-tailoredReport


Mobile Device’s brand name and

model

Source Code RetrieverSource 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

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 RetrieverDevice 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

CC/PP file

Device Information

Retriever

Jena

WURLF API WURLFprofiles

UAPRofprofiles

• Required data are extracted and a CC/PP file is created

• Both sources have complementary information


Extending mobileOK Basic testsExtending 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_SCRIPTSprf:JavaScriptEnabled

• Information to be retrieved are the issues that the DDC captures: character encoding, image format support etc.


Guidelines InstantiatorGuidelines 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

• Once the guideline is completed XQUERY tests are dynamically created

XQUERY tests

mobileOKtests

CC/PP file

Guidelines Instantiator


Guidelines InstantiatorGuidelines Instantiator


• Example for the IMAGE_MAPS test

XQUERY tests

mobileOKtests

CC/PP file


<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 excerptCC/PP excerpt

UGL excerptUGL excerpt

let $tmp:=web_doc.xml//OBJECT[@ismap] return if(not( ))thenfor $i in $tmp return<error>{$i/@line, $i/name()}</error>

XQUERY testXQUERY test

true

true


Evaluation EngineEvaluation Engine


• Summary:1. Web resource is retrieved changing HTTP

headers2. Information regarding the device is

retrieved from profile repositories and a CC/PP file is created

3. Slots in guidelines specifications are filled in with CC/PP data and XQUERY tests are automatically created

4. XHTML file is evaluated against the dynamically created queries and a device-tailored report is obtained

Evaluation Engine

EvaluationReport

Source Code Retriever

XHTML file

WWW

XQUERY tests

mobileOKtests

CC/PP file

Device Information

Retriever


JenaWURLF

APIWURFLprofiles

UAPRofprofiles

• Once we have a set of XQUERY tests evaluation is straightforward using XSLT processors


Case StudyCase 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


Case StudyCase 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 ↓


Last remarksLast 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/


Conclusions & Future WorkConclusions & 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


Evaluating Web Evaluating Web Accessibility for Specific Accessibility for Specific Mobile DevicesMobile Devices

Markel Vigo, A. Aizpurua, M. Arrue and J. Abascal

Laboratory of HCI for Special Needs


University of the Basque Country

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Evaluating Web Accessibility For Specific Mobile Devices