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Re: [xml-dev] Notable declarative expressions?

There's a grand unified theory of data modelling: Description Logics
(the model theory underlying OWL2 aka the semantic web), which is
about the best motivated theory there is for these kind of problems.

Specifically, I guess you could model XSD grammar constraints using
the description logic EL++ which, roughly speaking, admits expressing
role inclusionship constraints as regular expressions over roles (and
even a larger class of constraints; eg. consider papers by Yevgeny
Kazakov), though to the best of my knowledge this hasn't been applied
to XML model theory.

But AFAIK the addition of general identity constraints (ID/IDREF)
makes this logic undecidable.

On 12/20/16, Michael Kay <mike@saxonica.com> wrote:
>> On 20 Dec 2016, at 17:57, Thomas Passin <list1@tompassin.net> wrote:
>> I think you could (or at least I could) think of a schema as a model.
> I'm inclined to agree. It's at least as much a data model as the schema of a
> relational database is. It defines a value space, and it provides mechanisms
> for documenting the relationships between values in the value space and
> things in the world outside. What else does it have to be to make it a data
> model?
> The fact that XSDs primary mechanism for constraining the value space is by
> means of a grammar is a distinguishing feature, but I don't see anything in
> the theory of data modelling that says "the constraints on the value space
> must be defined using mechanisms other than grammars".
> Michael Kay
> Saxonica
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