Database-valued attributes?

There's been the occasional incidental discussion of relation-valued attributes on the list lately. This has got me thinking: what about database-valued attributes? That is to say, what about an attribute that consists of a set of relation values?

The reason I ask is because I have been thinking about expressing trees as values. The canonical logical representation of a tree from "Practical Issues in Database Management" is a pair of relations: one for nodes, one for edges.

If one wanted to have an attribute that belonged to the tree domain, one would need to support an attribute with such a pair of relation values.

Does this raise any problems? I don't see any immediate issues, but it's not an idea I've ever heard mentioned anywhere else.

Comments welcome, including alternative ideas.

Marshall Received on Mon Nov 10 2003 - 23:40:10 CST