Re: [xml-dev] RE: Declarative programming requires a different mindset

[Frank Manola <fmanola@acm.org>]

Roger--

Your diagram doesn't really constrain the possible answers very much, since as literally stated a label for the big bubble could be, for one example, "things we talk about on xml-dev", or "things I thought about today".    I suspect you had something more specific in mind.  How about "computer-related languages"?  Since the context is computer languages, the "for solving problems" part seems redundant.  Can you think of any computer languages that can't be described as being for solving some kind of problem?  

Also, I believe thinking of a schema language (of any kind) as necessarily related to declarative programming confuses things.  Schema languages started as a way of separating the data declaration parts of programs (like declarations of variables and their types) from the imperative parts.  In fact, I believe they started with the data division in COBOL (certainly not a declarative programming language).  The first use of "schema" to describe one of those separate data specifications was, I believe, in the CODASYL Data Base Task Group specifications (to describe the overall database structure), which were derived somewhat from COBOL ideas (the chairman of the DBTG was Greek, hence the term "schema").  

--Frank

On Apr 11, 2010, at 4:29 PM, Costello, Roger L. wrote:

> 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
> 
> 
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