For those of you struggling with metadata concepts
Phil Howard of Bloor Research has one of the most straightforward articles on the difference between data and metadata I've run across lately:
Posted by Mitch Ratcliffe at January 31, 2003 08:56 AM | TrackBack
"...relational databases store tables which define entities. That is all they store. They also contain details about relationships that are defined by means of such things as foreign keys. However, these relationships are not explicitly stored in the database, which is why they are called relational, because that information is implicit.
When you are manipulating metadata, however, your needs are rather different and you do actually need to store relationships because you can have relationships between relationships (dependencies for example)."