Is XML accessible?

DO-IT Factsheet #1026

XML is short for Extensible Markup Language and is a specification from the World Wide Web Consortium (W3C). It is not a replacement for HTML but is one level up: It is a meta-syntax, used to define new markup languages. XML's key benefits are its extensibility (XML-based languages can be extended with new custom tags) and its portability (XML-based languages can be used across different platforms and devices).

XML can be good for accessibility. With XML, content is entirely independent from structure. Therefore, a single content file in an XML language can be rendered differently to different users, so users of screen readers, Braille output devices, graphic browsers, and small handheld computers, for example, can all receive the same information but have it presented in ways that make the most sense for their unique devices.

XML is already having a significant impact on web-based education. Historically, there have been major limitations in the content that could be displayed with HTML. Mathematical notation, for example, could not be displayed with HTML, so instructors would rely on workaround techniques such as GIF images of mathematical formulas, which blur when enlarged and usually aren't accompanied by alternate text. Many languages have been developed with XML that are eliminating these types of barriers. The following are a few examples, including the accessibility implications of each:

The IMS Global Learning Consortium, an organization that is developing and promoting open specifications for online distributed learning activities, strongly recommends XML in its IMS Guidelines for Developing Accessible Learning Applications [11] and devotes an entire section (section 4 [12]) to using XML for accessibility.

However, XML is not without potential accessibility problems. The primary accessibility issue is that developers can use XML to create inaccessible languages. HTML, for example, provides a tremendous variety of accessibility features in its specification ("alt" attributes for images, title attributes for frames, etc.). Web designers don't always use these features, but at least it's possible to design an accessible web page with HTML. XML gives developers tremendous freedom to develop their own languages, and with this freedom there is the possibility that some new languages will provide no means of making content accessible. To address this issue, the W3C's Web Accessibility Initiative (WAI) has developed guidelines for designing accessible applications with XML. The XML Accessibility Guidelines [13] is currently a work in progress. It's a reasonable assumption, however, that not all XML developers will create accessible languages. In Section 4.2 of the IMS Accessibility Guidelines (cited in the preceding paragraph), IMS recommends that authors "seek to confine their selection of special-purpose XML languages to those already in general use, especially those languages designed with accessibility provisions."