I'm not quite sure what you're describing, David.
Are you strictly talking about a data model capable of storing the
relevant information about each CD, or are you talking about an
online service that would allow owners of the CDs to download that
information?
I'm talking about both. The online CD databases are wholly
inadequate for anything but the most basic identification of the
CDs. They use data that comes from the manufacturers of the CDs, who
are concerned with the object, the CD, not with its content, which
is inadequately documented in the data structures that they use.
This is universal in the commercial recording world.
Without the latter, it strikes me that the former isn't of that
much use to someone who wants to automate the capture process.
(although, of course, it'll be a big boon for people who are
willing to key the information in themselves)
It depends on what you want. Do you want to catalog it properly, or
do you want to catalog it using the priorities of the manufacturers
of the recordings? Or the priorities of people who don't have any
Classical music?
I'm sure the online CD database information could be easily
incorporated into a proper schema, but you'd have to know the schema
the online CD databases were using, and I'm not certain they are all
using the same one (though I haven't checked -- I don't rip any CDs
except those created from recordings of my own group, so I have
never even once acquired any data from any of those databases).