2.1.1. Content Formats: Rich Internet Applications

[ysmartin]

In addition to DOM, CSS, and JavaScript, web content may also include embedded content such as Accessible Rich Internet Applications (WAI-ARIA [WAI-ARIA]) that is critical for accessibility

Suggestion:
The extensive use of DOM, CSS, JavaScript and sometimes other technologies, allows creating web content showing complex behaviours, known as Rich Internet Applications (RIAs). Beyond the accessibility of the underlying technologies, the accessibility of RIAs requires its own consideration ([WAI-ARIA])

Note: the rest of the paragraph would need to be reworded a little to accommodate the mentions to SVG and MathML.

Rationale:

1. Rich Internet Applications are more than just DOM+CSS+Javacript, but it is not correct to say that they are included in addition to those; as RIAs are indeed made by combining these technologies. RIAs are an emergent behaviour, just they play at a higher abstraction level.
2. What are usually included are RIAs (accessible or not), not ARIAs. The references to "accessible" and WAI-ARIA would only fit at the end of the sentence, when the criticality for accessibility is discussed.

I am quite, but not completely happy with my own suggested text, but it sketches out the approach.