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Generating instances from schemas usually just produces one of the
infinite number of instances restricted by certain trivial parameters. I
don't know of an example where meaningful instances are generated.
If a generated document changes automatically depending on the schema it
finds at the time of generation yet somehow contains the same
"information", there must be a model of the document that is independent
of the schema, e.g., something like an ER model. Then the model must be
populated: this concrete entity has that relationship to these other
concrete entities, etc. Then there must be a mapping from the abstract
document model to the elements and attributes used in the schema. When
the schema changes, the mapping must change in concert (and there must
be a way to prevent changes to the schema that violate the abstract
document model, e.g., changing an unbounded relationship to a bounded one).
After that, piece of cake. ;-}
Bullard, Claude L (Len) wrote:
> This one is fun. I know that a validating editor
> can use a schema or DTD to create a valid file.
> Can a program do this for files it creates dynamically?
> Are there examples of this?
> This question came from a programmer who doesn't want
> to hardwire the structure of files she creates into
> the code that creates them. I had replied with validation
> on input (create the file, validate it then), and what
> she actually wants to do is use the schema to drive
> the file builder using say, SAX or its analog. Mainly,
> she doesn't want to rewrite the code when new versions
> of the document inevitably occurs. She just wants to
> modify the schema. Works for editors but of course,
> they run in human time, but other than performance, I
> can't think of a reason WHY she couldn't do it.
> What about it?