I'm looking at something to design ERDs with, and while anything can suit my needs today, I'm not sure what capabilities I'll need in the future...(e.g. reverse-engineering, automatic code and DDL generation, UML support, integration with Eclipse, etc)

How easy is it, in the experience of anyone reading this, to migrate data models from one tool to another? Is there a standard file format in the back-end that makes it as simple as opening a file in another tool, or is it as painful as starting from scratch and doing it all manually?

I'd like to add a vaguely related question:

Can an ERD be expressed in UML as opposed to another notation like IE or IDEF, or are they unrelated concepts?

Is there anything that ERDs can express that UML cannot? I've looked at both diagrams, and I can't really tell... Of course, UML is meant for objects and can express things like methods and whatnot, but could it still be used as an ERD notation as opposed to IE, IDEF, etc?

Totally new to diagramming, perhaps somebody can advise on this matter?

It is possible to build pseudo-ERDs with UML's class diagrams. These can show entities as objects, attributes as attributes, relationships as associations (or whatever UML calls arrows) with cardinality marked on each end something like 0..*.

One thing they can't show is unique identifiers, I think because OO has no equivalent concept (every object has an implicit Object ID). I think you can show these only as comments linked to the object box somehow.

I read an article about this by Scott Ambler - you could Google for that. He makes my blood boil, but it just may be relevant to what you want.