Note: The following text is identical to that in Draft 5 and on the Expert Handlers SIG's front page; only the markup has been changed to point to internal, rather than external resources.
Generalized content markup (such as HTML) is complimented by markup specifications that facilitate more semantically precise content markup. Examples of specialized, semantically precise markup include MathML and MusicXML. Assistive technology (AT) typically handles generalized content markup, but does not know about specialized markup. Because of this, users of AT are unable to access or navigate specialized markup effectively.
The Open A11y Expert Handlers SIG is exploring a standardized plug-in mechanism to AT software. The goal of this plug-in standard is to allow AT software to take advantage of expert software that understands specialized markup. This plug-in standard will allow the expert software to provide enhanced, semantically rich access to specialized markup so that the AT can properly render (visually, aurally, and/or tactilly) and help users navigate the semantic meaning encoded in the specialized markup.