Just been reading some interesting articles on the "Semantic Web" (term originated by Berners Lee).

XML seemed an obvious extension of HTML - you could invent your own syntax.

RDF seems an obvious extension of this - you can express object relationships in a regular way.

On a practical note I think RDF might be a useful language for expressing entity models when developing computer systems.

It could be used to generate database schemas, and the "glue" code necessary for adding, editing, reporting and deleting (CRUD) entities.