After more than a decade of work, AES finally has published two important audio metadata standards.
AES60-2011: AES standard for audio metadata – Core audio metadata
This specification addresses the creation, management and preservation of material that can be re-used as originally produced, or may provide input material for new production projects. Material is expected to be exchanged between various organisations or between production facilities in a distributed environment.
AES57-2011 sets out the vocabulary to be used in describing digital and analog audio formats, including both those formats that exist in some tangible form such as a reel of tape and those that exist only as a set of bits, untied to a single audio carrier, such as a broadcast wave file.
Update: So far the actual schemas don’t seem to be online. I’ll post their URL’s as soon as I find out where they are.
Mad File Format Science 