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RE: [xml-dev] Declarative programming requires a differentmindset

A formal logic expression language
In the case of W3C Schema, one optimised for expressing constraints on a data model.

There are very many formal logic, class and ontology expression and description languages and they  have been a major player in the development of computing and mathematics since Aristotle. Programming languages are a subset based on the concept in maths of the 'program'. The idea of a logical expression language predates programming though in that its proponents were some of the philosophers whose ideas predated the kinds of maths which included programs. Computers are devices for making sense of some of the logic languages. They happen to use programs to do it (so far) so have become particularly associated with programs but that is only their means to an end. Their purpose is to handle logical statements written in logic expression languages/symbols and make sense of them.

Stephen D Green

-----Original Message-----
From: Costello, Roger L.
Sent:  11/04/2010 9:29:38 pm
Subject:  RE: [xml-dev] RE: Declarative programming requires a different mindset

Hi Folks,

If XSD is not a programming language then what is it?

People have said that XSD is:
   - a declarative language 
   - descriptive markup

I think that a programming language is a syntax for solving problems (where the syntax is such that it can be processed by a computer).

XSD is a syntax for solving certain problems. Specifically, XSD is for solving constraint problems, i.e.,

    Is the input ____ constrained in this ____ way?

A computer can evaluate an input document against an XSD document and produce an answer to the question, i.e., using the XSD language the problem can be solved.

I understand that the set of problems that can be solved using XSD are very specific.

People have said that a programming language is one that can solve many different kinds of problems. Certainly, then, XSD is not a programming language.

Both XSD and programming languages are languages for solving problems. So, if I were to draw a Venn diagram I would draw a:

   - bubble for XSD
   - bubble for programming languages (independent of the XSD bubble)
   - put both of the bubbles inside a big bubble

What would you label the big bubble?

Here's a graphic to illustrate my question:




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