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Re: [xml-dev] Notable declarative expressions?


I generally agree with what you said, with one exception.

You asked "What else does it have to be to make it a data model?"

In my education, a data model incorporates the operations/functions/behaviors (OFBs) for the things described by the model. In the relational model, for example, the various OFBs of relational algebra (cross product, projection, filter, grouping, etc.) and relational calculus (e.g., relational division) all form an important part of the model.

Hope this helps,

On 2016-12-20 11:04, Michael Kay 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

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