W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2001

Re: rdf as a base for other languages

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 1 Jun 2001 17:46:50 -0500
Message-Id: <v04210116b73dc5cb46fa@[]>
To: las@olin.edu
Cc: www-rdf-logic@w3.org
> > >In message <20010601130755B.pfps@research.bell-labs.com> Peter wrote:
> > >
> > > >For example, suppose that you wanted to represent propositional formulae
> > > >within RDF.  You might do something like:
> > > >
> > > ><rdf:type x OR>
> > > ><component x y>
> > > ><component x z>
>(and a lot more RDF).  Then pat hayes wrote:
> > So, to return to Peter's example: if OR is supposed to be what it
> > started out as being (before Peter encoded the logical disjunction
> > into RDF), then something needs to know what its truth-conditions
> > are: how the truth of a disjunction depends on the truthvalues of its
> > compnent subexpressions. But in the RDF encoding, that information is
> > not provided as part of the RDF model. So this encoding is not a
> > translation of a disjunction into RDF.
>You are absolutely right.  By itself -- in the absence of an understanding of
>how to interpret the squiggles of RDF

My point was that even with a (full) understanding of how to 
interpret the RDF, it still wouldnt be a translation of disjunction. 
Disjunction is not expressible in RDF.

(I might add that I would not keep going on about this if people 
(like Sandro) didnt keep saying the opposite.)

>-- this is *not* an encoding of a
>disjunction in any proper sense.  Further, RDF itself gives NO SUCH

Well, I'm glad we have that clear. (BTW, can you say what it is that 
you see RDF as actually providing? (Serious question, not just being 

>That's why various people are trying to write rules for RDF (or RDF-derived
>languages):  to provide the "something" that needs to know what
>truth-conditions are,

There is a slight problem here. If indeed RDF is an assertional 
language consisting entirely of ground atomic assertions ("binary CE 
logic"), then there is little point in trying to write such rules. 
There are easy proofs that no such rules can be written. Maybe it 
would be more profitable, therefore, to choose some other goals.

However, the fact that these proofs are so obvious, and that so many 
smart people continue to want to develop rules of this kind, makes me 
think that maybe this way of interpreting RDF is not what the 
founders intended, in fact.


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Received on Friday, 1 June 2001 18:46:58 UTC

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