W3C home > Mailing lists > Public > www-rdf-interest@w3.org > April 2001

RE: N3 contexts vs RDF reification

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 26 Apr 2001 11:59:53 -0500
Message-Id: <v04210108b70e00301a46@[205.160.76.196]>
To: Lee Jonas <lee.jonas@cakehouse.co.uk>
Cc: "'Seth Russell'" <seth@robustai.net>, <www-rdf-interest@w3.org>, Tim Berners-Lee <timbl@w3.org>, Guha <guha@alpiri.com>
>
>My understanding:
>
>Summary
>=======
>There are at least two competing proposals for representing contexts in RDF.
>The concept of 'context', although similar, differs slightly with respect to
>'higher-order' statements, ('reification' and making statements about
>statements).

I wonder, could I make a plea that y'all change your terminology here 
slightly? The term 'higher-order' already has an accepted usage now 
for about80 years, and it isn't this, so this is likely to cause all 
kinds of confusion and wasted time. What you are talking about is 
meta-language statements (statements about other statements), not 
higher-order statements.

What makes something higher-order is that it involves quantification 
over a universe of relations or functions, as when you might be able 
to infer from (P a c) and (Q b c) that there exists a relation [P or 
Q] which holds between both (a c) and (b c). Often, though not 
always, higher-order logics use some kind of lambda-conversion. Being 
higher-order is connected in various ways with set theory (in 
mathematical logic, relations are sets), and the 'higher' in the name 
refers to a set-theoretical heirarchy, not a language/metalanguage 
heirarchy. These havn't got much to do with one another, and I don't 
think that being higher-order is likely to be of much interest to RDF 
or Web logics more generally.

Traditional logic has studied higher-order logics and set theory in 
excruciating detail, but it hasnt paid quite so much attention to 
language/meta-language heirarchies.

Pat Hayes

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Received on Thursday, 26 April 2001 13:00:03 GMT

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