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Re: properties as nodes etc.

From: Seth Russell <seth@robustai.net>
Date: Sun, 30 Jun 2002 10:43:25 -0700
Message-ID: <001401c2205d$a3b9b7e0$657ba8c0@c1457248a.sttls1.wa.home.com>
To: "tim finin" <finin@cs.umbc.edu>, "Enrico Franconi" <franconi@cs.man.ac.uk>
Cc: <www-rdf-logic@w3.org>

if you want to expliticidly designate that each event is unique, then give
it a uri, instead of leaving the node anonymous.  Otherwise just continue to
add restrictions until only one such event can qualify.  I  guess I don't
see the problem.

Seth Russell

----- Original Message -----
From: "tim finin" <finin@cs.umbc.edu>
To: "Enrico Franconi" <franconi@cs.man.ac.uk>
Cc: <www-rdf-logic@w3.org>
Sent: Sunday, June 30, 2002 9:47 AM
Subject: Re: properties as nodes etc.

> Pat describes a very common way to encode n-ary relationships using binary
> relations in the context of natural language processing. I think of his
> example as underlyingly being a four argument relationship, with the
> argument being the identifier of the "anonymous node" in RDF.  Thus, one
> have two (indefinite) descriptions
>   a sitingsOn with agent=cat, object=mat, duration=hour.
>   a sitingsOn with agent=cat, object=mat, duration=hour.
> and it's ambiguous as to whether these two descriptions are of the same
> or different events.  Each would be encoded as a different individual
> of type sittingOn.  If we wanted to support this, which again can
> be motivated by the demands of modeling the semantics of natural language
> expressions, how would you do it?
> Enrico Franconi wrote:
> > On June 27, pat hayes writes:
> > ...
> > > One tried-and-tested idea is to introduce an explicit category of
> > > events, and connect everything else to them.  Then your example
> > > would look like this in Ntriples:
> > >   _:x  rdf:type sittingsOn .
> > >   _:x  agent cat .
> > >   _:x  object mat .
> > >   _:x  duration hour .
> > > where you would also know that
> > >     sittingsOn rdfs:subClassOf events .
> > > and you could then say other things about that sitting as well, such
> > > as why it happened and what its results were and who told you about
> > > it, and so on. You could even say that it never happened or was
> > ...
> > The above encoding of a ternary relation in a binary relational model
> > (like RDF) would be wrong, and in fact it can not be done in RDF at
> > all. In fact, you are missing the information that there is a unique
> > instance of the ternary relation for each triple of arguments. So, the
> > original information stated in the graph making use of the ternary
> > relation says that given a cat, a mat, and a specific time, then there
> > is a unique instance of the ternary relation (in this case, the event
> > of sitting). In your weaker encoding, you may have more than one
> > instance of the event for each tuple in the original n-ary
> > relation. Clearly, you violate the semantics of n-ary relations, by
> > admitting basically that a tuple may appear more than once in the
> > relation.
Received on Sunday, 30 June 2002 13:49:51 UTC

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