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Re: Issues danc-01 Re: 2 formalities in RDF concepts

From: Jan Grant <Jan.Grant@bristol.ac.uk>
Date: Tue, 28 Jan 2003 21:59:55 +0000 (GMT)
To: Dan Connolly <connolly@w3.org>
cc: Jeremy Carroll <jjc@hpl.hp.com>, RDFCore Working Group <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.GSO.4.44.0301282151060.4421-100000@mail.ilrt.bris.ac.uk>

On Tue, 28 Jan 2003, Dan Connolly wrote:

> JJC wrote:

> > see:
> > 3.6 Graph Equality
> > http://www.w3.org/TR/2002/WD-rdf-concepts-20020829/#xtocid103648
> > (which uses both terms)
> >
> > If I have two N-triple files of one line each
> >
> > <eg:a> <eg:b> _:x .
> >
> > and
> >
> > <eg:a> <eg:b> _:y .
> >
> > Do you think they are equal or unequal?
> Those two files are clearly distinguishable, hence
> they are not equal.
> > Personally, I would say they are equal as RDF graphs, and unequal as text
> > documents.
> "as RDF graphs"... I'm not sure what you mean by that, formally.
> I don't think you mean that N-triples file are RDF graphs.
> I think you mean that there's a straightforward correspondence
> from N-triples files to RDF graphs, and that the
> two distinct N-triples files above correspond to the
> same RDF graph.

Jeremy's talking about *syntactic* equality (ie, "X equals Y" means
"every expression involving X can be rewritten with Y substituted for it
and the expression's value is preserved"), not identity (X and Y can be
equal but not identical; if X and Y are identical then they're equal).
This terminology is used (in my experience) by some mathematicians but
not all; depends on the field and personal choice. In the sense it's
used it's ok (I think) so it comes down to choosing a terminology and
sticking to it. If this is going to cause wide-scale confusion it might
be better to revert to couching this in terms of "isomorphism" which is
a less overloaded term.

Received on Tuesday, 28 January 2003 17:02:53 UTC

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