2000 Conference Proceedings

Daniel Dardailler
Project Manager, Web Accessibility Initiative
INRIA, Sophia-Antipolis, France
World Wide Web Consortium
Email: danield@w3.org Website: http://www.w3.org/WAI

This document introduces concepts related to XML Accessibility and provides guidelines for new DTD/Schema/Profile designers and editing tool developers. Compared to HTML or SMIL, XML is one level up: it is a meta language used to describe new languages, and in addition to the usual device independence issues, we need to pay attention to the issue of conveying semantics for otherwise unknown grammar. The session will present the latest work in this area from the World Wide Web Consortium's (W3C) Web Accessibility Initiative (WAI).

XML (Extensible Markup Language) is a meta-syntax, used to declare grammars (called DTD, Document Type Definition - but see the caveat about our use of the term DTD in the definition section at the end of the paper) for new computer languages and formats (called markup languages). These DTDs can be classified along two different axes:

This document only addresses User-centric DTDs. This does not imply that the first type of DTD doesn't have accessibility issues or features (see how XSL can help Braille formatting, for instance). However, since they do not directly convey information presented to the end-user, they are out of our scope here. In a sense, machine-centric DTDs have no connection to user interface accessibility, and one might ask if the commutative proposition is true: DTDs with no accessibility issues are the ones that must reach the right level of machine-centricity.

For User-centric languages, the message is simple: be device independent and export your semantics as much as you can. While the priority is stronger on the first aspect (multi-modality), both aspects are important, as without the knowledge of the meaning of the XML elements and attributes, there is little chance that alternative user agents can do something intelligent with just the document bits.

This semantics knowledge can be provided through human readable documentation, but having machine readable assertions of some semantics that can then be used to present the document in various media is paramount for pervasive access (i.e., you don't need a programmer, you just need a program). The ICADD (International Committee on Accessible Document Design ) committee was a pioneer in this topic, for SGML accessibility and ways to convey arbitrary DTD semantics (using specific SGML binding mechanisms). A few years later, ICADD has not really been adopted, and people are still trying to solve the same problem, albeit with more experience in the field of HTML accessibility, and applied to XML this time.

This section provides a list of abstract guidelines, checkpoints and techniques that DTD designers should follow to achieve accessibility when designing new UI XML DTDs. At the time of writing the article, this is still in draft stage ,and people are encouraged to check the WAI site for a mroe updated version.

The techniques are meant to point at existing or new mechanisms used to implement these guidelines through re-use and modularization of XML parts. A note at the end of this document explains why to distinguish guidelines and techniques.

In this paper, we examined how to provide clear definitions and requirements related to XML accessibility. We believe abstract guidelines and verifiable checkpoints/techniques (using implementation mechanisms associated with abstract guidelines) are the best way to address this problem. Our primary message is: be device independent, and export your semantics as much as you can. We proposed five different guidelines for doing that:

DTD:

Even though we use the acronym DTD, we don't want people to assume we are only talking about a DTD as defined in XML 1.0 but rather some document or collection of documents which contains all the references for interpreting a document which is encoded in accordance with the usage of some application or community of discourse. Schema or profile might be a better word for our usage.

Accessible DTD:

An XMl DTD is accessible if it enables and promotes the creation of accessible documents

Accessible document:

A document is accessible if it can be equally understood by its targeted audience regardless of the device used to access it.

Promoting vs. enabling:

The word "promote" is important as "enable" alone does not cover the case where a DTD could include some open string representation somewhere and claim minimal accessibility.

To take an example, suppose HTML didn't have an ALT attribute on IMG, it would still in theory "enable" the creation of accessible documents, since HTML files carry textual content and one could always describe images inline, as in

<IMG SRC="Tax.gif"> How pay your taxes

but this doesn't "promote" accessibility as most author will not want to repeat "How to pay your taxes" if the logo already says "How to pay your taxes" (assuming CSS cannot be used for that). Having ALT "promotes" accessibility as it allows images to be described without performance loss - such as duplication - for image viewer.

In any case, accessibility is not just about alternative content, as the next section will show.

Device:

The word "device" is also important as it encompasses more than just media independence: it's both output (graphical, voice, braille, text-only) and input (mouse, keyboard, voice, keypad, one-touch). This term also potentially carries with it the issues related to high bandwidth availibility (or lack thereof), where access to data becomes impossible on slow connection because of their volume.

Equal understanding:

The term "equal understanding" is critical as it permits some form of graceful transformation when presenting in one media content primarily designed for another media.

XML and Accessibility