IBM's XML for Java is designed to support something like what
you describe.
>I believe Larval may have this kind of capability (i'm not sure yet),
>are there others?
Larval doesn't have it built-in, but it parses content models
into a fairly straightforward set of data structures, and you could
certainly generate this kind of thing by writing code that runs
around them. But it would be work. -T.