Opera is is working on a Multimodal Browser that is based on the XHTML+Voice specification, version 1.2. The W3C hosts a note of XHTML+Voice, which was created in 2001 and I guess it is unlikely that the Voice Working Group is going to do more work on it, but you never know. The 1.2 specification defines a profile that contains parts of VoiceXML 2.0, XHTML 1.1 and XML Events. One of the people working at Opera provides more information and what I really like is that they are going to support the CSS3 Speech Module, which is currently a working draft. (Opera is already pretty advanced with support for 'screen', 'print', 'projection', 'mobile' and probably others.)
According to a list of supported properties (there isn't official documentation yet) it seems that the Multimodal Opera Browser supports quite some speech CSS. The properties that come from the CSS3 working draft are prefixed with '-xv-', something I don't really understand since Opera used to use '-o-' for extensions and such, but at least they use a prefix. I have read the specification and the new properties are based on the model described in the SSML specification. What I don't really understand why we need separate markup languages for Voice environments. If we need such things, we need to adjust markup for the end user and everything gets to a higher level of complexity (the same for things like XHTML-Print). Providing a speech style sheet is easy, generating new markup if a browser accepts application/x-xhtml-voice+xml is difficult and way more complex. Related reading:
Upon reading your comment, and taking a quick glance at the w3c drafts that you linked to, I was quite exhausted. My mind seems ready to explode with that information in mind. It is an interesting specification which I will most definitely keep an eye on.
I have to applaud what the Opera group are doing. Although their product has an interface I've always disliked, they've excelled at producing a browser worth paying for. Accessibility is one of the flags I like to fly and this specification seems to go a long way with that in mind.
You have me thinking now what more I can be doing to make my xHTML more accessible
Paul Connolley: Although their product has an interface I've always disliked
The interface can be changed in many ways.
Anne: envirements
Did you mean 'environments'?
Fixed that, thanks.
The best part of blogging vs. journalism is the free copy editing :)
The properties that come from the CSS3 working draft are prefixed with '-xv-', something I don't really understand since Opera used to use '-o-' for extensions and such...
If I were to guess, I'd say it's either because the voice components were developed together with IBM (ie. they're not strictly Opera work, so the -o- prefix is too specific) or a different prefix was used simply so that you could more easily identify voice properties.
I'm just guessing, though, of course.