As a client developer, I'd want to ask what metadata might be useful to clients first and foremost. Come up with some use cases that amount to more than just "have metadata - must publish".
It seems to me that it's one of those potential edge cases where we may end up arguing ad libitum without reaching an agreement because not everyone uses the Atom format with the same expectation. Atom may have come from the blogging world but it's pretty clear that it gradually becomes the de facto envelop format for any kind of exchange.
Personally I'm not sure whether or not this thread is about "extending the atom vocabulary with common metadata about media resources in order to enrich Atom" or "defining developers' best practices for inlining metadata with their own namespace in an Atom document".
The former point is quite interesting to me since we could capitalize on Atom being seen as a clean and versatile standard and propel the next media metadata storage and exchange format with it.The latter point seems simply a case of using atom:content with an appropriate media-type.
However if we decide to extend the atom vocabulary like Yahoo did with Media-RSS, we ought to actually discuss first with the main players in the field today (Apple, Microsoft, Xiph, EXIF, etc.) in order to define the minimal relevant set of metadata for common media formats. In some way maybe should we expand on the discussion taking place at the microformats wiki [1].
- Sylvain [1] http://microformats.org/wiki/media-metadata-examples
