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Re: Review of "Storing Data in Documents"

From: Elliotte Rusty Harold <elharo@metalab.unc.edu>
Date: Wed, 23 Mar 2005 07:49:33 -0500
Message-ID: <424165DD.8060600@metalab.unc.edu>
To: Graham Klyne <GK@ninebynine.org>
Cc: Dan Connolly <connolly@w3.org>, noah_mendelsohn@us.ibm.com, Chris Lilley <chris@w3.org>, "Henry S. Thompson" <ht@inf.ed.ac.uk>, www-tag <www-tag@w3.org>

Graham Klyne wrote:

 > In short, as I understand the term, "declarative" can be "Turing
 > complete".  I thought that was what XSLT (along with functional
 > programming languages) actually achieves.

XSLT is functional. It is not declarative. SQL is declarative*, and it 
isn't Turing complete. It might be possible to make a declarative 
language Turing complete, but I'm not sure what the point would be. The 
goal of a declarative language such as SQL is to describe the result you 
want and allow the computer to determine the algorithm it uses to 
calculate that result. Programming in a Turing complete language 
generally involves specifying an algorithm.

* People do argue that SQL isn't truly declarative, but it's as close as 
any major language a lot of people are likely to know.

Elliotte Rusty Harold  elharo@metalab.unc.edu
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Received on Wednesday, 23 March 2005 12:49:34 UTC

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