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Re: RDFCore Update

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 19 Oct 2001 07:33:18 -0400
To: tpassin@home.com
Cc: www-rdf-interest@w3.org
Message-Id: <20011019073318U.pfps@research.bell-labs.com>
From: "Thomas B. Passin" <tpassin@home.com>
Subject: Re: RDFCore Update
Date: Thu, 18 Oct 2001 23:52:44 -0400

> [Peter F. Patel-Schneider]
> 
> >
> > I don't know how you could handle a prescriptive meaning for rdfs:range in
> > an open environment.  You certainly can't say that the target object has
> to
> > belong to the range when the triple is read because there is no notion of
> > order in RDF.
> 
> But that only means that you cannot validate the graph until the whole thing
> is constructed.  That's no different that for XML Schema itself.  Why do you
> think that would be unworkable?  It would let you separate graph
> construction and validation into separate processing layers, which should be
> good not bad.
> 
> Cheers,
> 
> Tom P

But the approach of waiting introduces non-monotonicity.

When do you know that you have everything you need?  RDF allows information
to be accumulated from multiple sources.  If you say that you ``validate''
when you have everything you know about, then you can have the following
situation:

An RDF system looks around to find all available information, and finds:

	John sister Susan .
	sister rdfs:range Person .

It complains that Susan is not (known to be) a Person. (How?  Well the only
way so far is to have no possible models.)

The user points out a new source of information that states

	Susan rdf:type Person .

and now the RDF system is perfectly happy.  Voila---non-monotonicity.

peter
Received on Friday, 19 October 2001 07:34:06 GMT

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