Is it possible to recognize when a caller has barged-in with DTMF? Is there something in VoiceXML like an event that I could catch?
The problem that I am trying to solve is we need barge-in to 'cascade' for several prompts so I was thinking of setting a variable if I could recognize barge-in and then skip over the next few prompts.
If your browser supports mark (see VoiceXML 2.1 Spec, section 4 Using mark to detect barge in during prompt playback), you should be able to detect barge-in. However, only a subset of browsers support mark and because DTMF is often detected on a separate path than speech, make sure your browser supports mark on both paths. In some cases, even the telephony protocol being used can impact whether the feature exists (again, an artifact of the technologies used to put the systems together).
One alternative that may work, depending on your browser, is to create a series of fields or forms. Each with a very short or non-existent timeout. Go forward on the default timeout path, but break if you receive a nomatch or match. This will work fine for some browsers, other may have noticeable gaps between the fields/forms.