At PDC (and before that on ObjectSpaces project), this was a hot discussion topic. What approach is better: attributes or external source like an XML file. I would like to open up this topic beyond the 1:1 conversations at PDC to the blogosphere. I will start with a small backgrounder and you tell us which one makes more sense to you.
Advantage external mapping
Of course, a natural question is why not support both? Well, as a user, which one should I choose? How do I decide? Do I need to learn both ways? As builders of the ORM component, do we split out resources on two things that achieve more or less the same result instead of focusing on one?
So what do you think. Do you have compelling scenarios that cannot be handled using one of the options?