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

["Costello, Roger L." <costello@mitre.org>]

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:

http://www.xfront.com/XML-Declarative-Programming/XSD-and-programming-languages-are-a-type-of-what.gif 

/Roger