The term "metadata" has for a long time been used in
completely different senses by different communities. In the
document world, metadata often means information about
instances that is not part of the "content" of the instance.
In database theory, metadata is usually information about
types. The term is generally wider than "schema": for
example an entity-type life history might be part of the
metadata but not part of the schema. In the data warehousing
world, the term "metadata" is also widely used, and I
suspect its meaning there is slighltly different again,
though I am not an expert.
To enable XML to achieve its potential to unify the worlds
of documents and databases, I suggest we avoid using terms
that these communities will interpret differently.
Mike Kay