Translation between DTDs, schemas, UML, and the like

[Jarle Stabell]

A. G. McDowell  wrote:
> 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?

I suspect such a product will eventually be available.
The major analysis work required to do a relational schema, object model 
and a schema/DTD for XML seems to be the same,  finding the 
entities/classes/elements/components/concepts (or whatever your favourite 
vocabulary/method calls them) and their relations (and some of the 
constraints of the relations, multiplicity typically being the most 
important)

When doing object models, you have many more choices for 
optimalization/design of the implemented structure towards your specific 
needs/applications than with the relational model. With XML, you 
unfortunately(?) at some point need to choose whether you should implement 
a concept as an element or an attribute (most DB/OO design tools forces you 
to take this similar decision "too early"), and whether you should 
implement/codify a relation using the tree-structure of XML (child 
elements), or whether to use IDs and IDREFs type of mechanisms.

I believe the major work in designing DTDs/schemas for XML, relational 
schemas and analysis/high level OO class diagrams could use the same 
tool/formalism, but that you at some level need to add some extra 
information/decisions dependent upon the "output format".


Cheers,

Jarle Stabell
Digital Logikk AS


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