RDF Techniques for WCAG support

Status Of This Document

This document is a draft document. It hopes to demonstrate the potential of RDF in providing Accessibility support. It is hoped that this could be developed further to create a WCAG (Web content Accessibility Guidelines) techniques document.

It is recommended that the reader familiarize themselves with web accessibility principals and techniques before reading this document. See www.w3.org/wai

Introduction - Why develop RDF accessibility techniques?

RDF can be used to make web content WCAG (Web content Accessibility Guidelines) compliant even when

1. The original rendering can not be changed
2. The content web author is not interested in accessibility
3. Content relies on markup languages that do not support accessibility,
4. Further, schemas can be annotated to increase the accessibility of any usage
5. Accessibility can be supported beyond the capacities of HTML - providing support for unambiguous content creation
6. Profiles can be attached to web content
7. Meta searchers can be performed based on accessibility criteria
8. In some cases it may be easier to provide accessibility through RDF as one statement can render accessibility multiple elements.

Thanks to the WAI PF group of the W3C - especially Charles McCathieNevile and Al Gilman.

Section one: Examples of how an RDF vocabulary could be used to fulfill WCAG 2.0

WCAG 2.0 advocates use of the following design principals:

• Perceivable. Ensure that all content can be presented in form(s) that can be perceived by any user - except those aspects of the content that cannot be expressed in words.
• Operable. Ensure that the interface elements in the content are operable by any user.
• Navigable. Facilitate content orientation and navigation
• Understandable. Make it as easy as possible to understand the content and controls.
• Robust. Use Web technologies that maximize the ability of the content to work with current and future accessibility technologies and user agents.

A particular strength of RDF accessibility techniques is creating understandable content using language referencing.

Language Referencing

Ambiguous use of language creates problems with translation, misunderstandings and accessibility for cognitive disabilities.Translation to symbolic languages or simpler language for cognitive disabilities can not be automated. A controlled language restricts author's ability to stylize and express them-selves.

But..by referencing textual content, it's meaning becomes unambiguous, translatable and machine-readable without restricting the author's use of language.

Default lexicons can be set and cascaded, so that a default word usage can be set as the primary definition in the high priority default lexicon

A default reference can be overridden with individual lexicon references and definitions.

RDF usage examples

Note: The examples are designed as a proof of concept. They may contain technical errors.

In the following example RDF is used to document conformance to WCAG 2.0.

<rdf:Description rdf:about="some xpointer or xpath to a document/ site or section of a document" type ="accessibilityAnnotation">

<ub: "x">conformanceClaim >

<ub:profile>aural rendering</ub:profile>
<ubs:technique>1.1.1</ubs:technique>
<ub:WCAG01>1.1</ub:WCAG01>
<ub:conformenceLevel>2<ub:conformenceLevel>

</ub:conformanceClaim >

></rdf:Description >


In the following example RDF is used to provide alternative text and a long description alternative text to a graphic. A non-script alternative is also given. This will make non-text content perceivable.

<rdf:Description rdf:about="some xpointer to image with mouse over script happening" type ="accessibilityAnnotation">

< ub:AlternativeContent >

<ub:profile>aural rendering</ub:profile>
<ubs:technique>1.1.1</ubs:technique>
<ub:WCAG01>1.1</ub:WCAG01>

"x"><seq>

<rdf:li><ub:alt value=alt text> </rdf:li>

<rdf li> <ub:longdesc value=long desc reference> </rdf:li>

<rdf:li> <ub:nonscript about =xpath relative to image of the script value=text> </rdf:li>

"mso-tab-count: 1"><seq>

</ub:AlternativeContent >

</rdf:Description >


In the following examples rdf is used to provide a link a phrase or word to a definition. This makes the text unambiguous.

<rdf:Description rdf:about="xpointer to text"type =ub:accessibilityAnnotation>

< ub:lexicon >wordnet/~wn/consept#10293829</ ub:lexicon >

</rdf:Description >

In the following examples rdf is used to provide a link a phrase or word to a summary and picture. This makes the text understandable.

<rdf:Description rdf:about="some xpointer to obtuse legal paragraph" type ="ub:accessibilityAnnotation">

<ub:AlternativeContent >

<ub:profile>simplified</ub:profile>

"mso-tab-count: 1"> <ub:WCAG02>4.1</ub:WCAG01>

<bag>

"x"> <rdf:li><ub:summary value="we own you from now on"></rdf: li>

"x"><rdf:li><ub:nonTextvalue="picture_of_ slave_in_chains.gif"></rdf:li>

"x"></bag>

</ub:AlternativeContent >

</rdf:Description >

References

[WCAG10]