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Re: ACTION: propose test case for scalar constraint with syntax

From: Pat Hayes <phayes@ihmc.us>
Date: Sat, 18 Dec 2004 22:28:38 -0800
Message-Id: <p06001f17bdeacd717038@[]>
To: Simon Raboczi <raboczi@tucanatech.com>
Cc: public-rdf-dawg@w3.org

A quick response. Like Kendall
I am very sympathetic to the idea of using triple syntax for 
constraints, and less worried than Kendall is about the awfulness of 
the collection/container syntax (It is indeed awful, but the 
collections at least are a familiar awfulness that we know how to 
code around.) However, there is another issue. Part of the very point 
of constraints is that they are not treated as patterns to match 
against, whereas triples in patterns are exactly intended for that. 
So making the constraints into patterns seems like it creates 
confusion. Your proposal to use the namespace to distinguish them is 
pragmatic, but seems to set a potentially dangerous precedent. What 
happens if someone wants to use this namespace in an ordinary RDF 
graph? Does a query which finds these triples in the target graph 
find itself obliged to match them and evaluate them? What if the 
graph asserts something that evaluates to false?

You argue that RDF is supposed to be universal, and yes indeed; but 
remember its a universal notation for propositional assertions, not 
expressions intended for evaluation. So I can see a good positive 
case for having distinct syntax for patterns to be matched against, 
and for expressions to be evaluated.

Anyway, its a good issue to have raised, thanks.

Pat Hayes
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Received on Sunday, 19 December 2004 06:29:33 UTC

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