What is the best way to model user defined hierarchical relationships in a database?

Question

Essentially, I want the user to be able to define a hierarchical model, but then I need to allow the user to store data within their defined model. Does this make sense? So the

Answer 1

I'm working on a similar issue although I need to support multiple hierarchies (one set of children, multiple hierarchical views). I've found Joe Celko's "Trees and Hierarchies in SQL for Smarties" (ISBN: 1558609202) useful. I'm still working on the problem but it comes up so often when discussing this topic that it seemed appropriate to mention.