I decided I should to a test installation of the ALOHA Server application, which CAREO uses as its metadata repository (CAREO is technically a client application of this server).
Grabbed the documentation, PHP files etc… and had it running in less than an hour on my TiBook. If you have more experience with MySQL, you could probably get it done in less than 30 minutes.
Pointed ALOHA at it, and added the first learning object within about 5 minutes of turning the lights on. Cool.
If you really want to play with a schema-agnostic xml database, in the context of CAREO and learning object repositories, give the ALOHA server a whirl. It’s currently a less-than-user-friendly install process, but once it’s up and running it just works.