Has anyone modeled extension or inheritance?

I am working on a relational model [ODBMS ideas? No, thank you! :-) ] for a Content Repository. I want to know if anyone has modeled something like the following before, and any pointers in the right direction are appreciated.

A document (D) contains a set of Fields(F). D can have multiple versions, each version has a set of fields in F. Multiple versions can share fields.

Document K can be created from D, by inheriting all fields D has. Afterwards, K can override any field from D. K can add its own fields. After extending, if D added/deleted/changed its fieldd, K sees the changes unless those fields are overridden by K.

K can be extended to make P. P's inheritance goes all the way to D.

A document can inherit from only one parent.

When a new version is made for parent, all its children automatically see the new version content, if those fields are not over-ridden. Received on Sun Apr 01 2001 - 03:31:53 CEST