Ray Ozzie has been asking some interesting questions about XML, RSS and iCalendar, and I think we have some answers, from work we have been doing for about a year on RDF and iCalendar. There has been an informal W3C taskforce on calendaring and RDF for some time, but this work got a kick-start at a workshop in Bristol, and has continued as software to convert iCalendar to RDF, testcases, chats on IRC, and email discussion. At this stage we have done about as much as we want to, and I am starting to pull together some documentation. the workshop report contains many usecases explaining why we wanted to use RDF (instead of some vanilla XML format like xCal) - most notably because we wanted to make it easy to mix together information from different namespaces with calendar information; for example foaf information about people, and geographical information, and RDF makes this easier. The result is an RDF schema and tests.
Below I've tried to answer some of Ray's questions.
"Has a method to embed iCal into XML ever been approved or agreed upon? If so, let me refer to it as xCal."
Yes - there's something called xCal, a DTD Internet Draft, which I can't find right now (coverpages article about it). I'm pretty sure that work has stopped on it.
"Has a method to embed xCal events/etc ever been suggested as a viable item type for RSS?"
Yes, there are at least two related activities: RSS 1.0 events module, and some attempts to embed RDFical in RSS 1.0 (try view source). The former is a draft, and one or two people are using it, but is very under-specified, making it difficult to write applications which use it. The latter is just a demo, but I think is roughly the right way to go from a modelling point of view.
"Has anyone built websites that publish venues' event calendars in such a format for subscription/aggregation?"
Yes, LTSN economics have a site using RSS+events module; as does the SWAD-Europe project (which I work on). A related project called Skical has published Swedish events in RSS+events+ some extensions.
"Has anyone built an Outlook or Notes adapter that publishes personal or team calendars to such a feed, OR"
Sort of, see the Retsina project, which uses an older version of an RDF calendar schema and can import into outlook.
"Has anyone built an RSS aggregator that can aggregate multiple calendar RSS feeds into a desktop or web calendar UI?"
yes, I have, although it's only a demonstrator. It's simple to do though.
"Has anyone built an RSS aggregator that can aggregate multiple calendar RSS feeds into your Outlook or Notes personal calendar?"
Not that I have heard of....
I hope that helps. I really think that some simple way of propagating events data as RDF would be a very interesting application indeed, and I'm anxious to help it happen.