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Re: RDF Abstract Syntax: a strawman

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 29 May 2001 10:05:09 -0500
Message-Id: <v04210103b73969ae7aa2@[205.160.76.203]>
To: Dan Connolly <connolly@w3.org>
Cc: www-rdf-logic@w3.org
>    % hmm... are predicates
>    % limited to constants?
>    % The RDF 1.0 syntax suggests
>    % so, but n3 doesn't have that
>    % restriction

It is conventional to so limit them, but we relaxed this in the new 
KIF without apparently causing enormous problems. When there are 
predicate variables it is difficult to prevent things like applying a 
predicate to itself (more generally, any 'loop' of applications, eg 
applying P to Q and Q to P) which breaks the 'standard' first-order 
model theory , but Chris Menzel invented a neat way to repair it 
without causing much harm, or one can be even braver and use a 
nonstandard set theory to do the semantics with. So in sum: go ahead 
and allow variables in predicate position, and if anyone accuses you 
of doing higher-order logic, send them to me.

Pat

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Received on Tuesday, 29 May 2001 11:05:17 UTC

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