Translation between DTDs, schemas, UML, and the like

[A. G. McDowell]

There seem to be a large number of languages devoted to listing (for
instance) the fields that make up a customer order and describing their
data types. To comprehend a (hypothetical) ecommerce system I might have
to follow a relational schema for the underlying database, a UML model
of the application classes and logic, and a schema or DTD for the XML
used to exchange data with its customers.

Is there any hope of a product that could be used to automatically
generate some part of this? My chosen format would be UML, but I'm open
to reasons why not. There are already drawing tools out there that can
generate C++ or Java code from suitably annotated diagrams, and keep the
annotations from making the diagrams unreadable: XML DTDs or schemas
should just be one more output format. The work on exchange of UML
between repositories already seems to involve auto-generating some sort
of schema from a description of UML (albeit not couched in UML itself,
but in a simpler metalanguage). Finally, there are a lot of people out
there who have already decided they need to know UML for the application
logic anyway.

On the other hand I don't know anywhere I can go to buy a UML -> DTD
Rational Rose plugin, complete with round trip functionality and a free
mouse mat, so maybe there's some good reason why all this is rubbish. Is
anybody planning to convert all the systems analysts to model in XML
schemas? Is the gap between exchangeable data, open to the world, and
encapsulated objects, observable only via their methods, just too large?
I have to admit that I personally have no great desire to write all my
Java via Rational Rose. Should I also find a burning desire to hand-
craft DTDs? 
-- 
A. G. McDowell

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