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RE: Syntax-level typing (was Re: A data typing proposal)

From: <Patrick.Stickler@nokia.com>
Date: Fri, 16 Aug 2002 17:04:42 +0300
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B160BBD@trebe006.NOE.Nokia.com>
To: <fmanola@mitre.org>
Cc: <connolly@w3.org>, <melnik@db.stanford.edu>, <guha@guha.com>, <w3c-rdfcore-wg@w3.org>


Thanks for the perspective, Frank. I can see how both
Dan and I can be correct, from our particular points of
view.

Patrick

> -----Original Message-----
> From: ext Frank Manola [mailto:fmanola@mitre.org]
> Sent: 16 August, 2002 14:49
> To: Stickler Patrick (NRC/Tampere)
> Cc: connolly@w3.org; melnik@db.stanford.edu; guha@guha.com;
> w3c-rdfcore-wg@w3.org
> Subject: Re: Syntax-level typing (was Re: A data typing proposal)
> 
> 
> Patrick.Stickler@nokia.com wrote:
> 
> >  
> >>-----Original Message-----
> >>From: ext Dan Connolly [mailto:connolly@w3.org]
> >>Sent: 15 August, 2002 22:24
> >>To: Stickler Patrick (NRC/Tampere)
> >>Cc: melnik@db.stanford.edu; R.V.Guha; w3c-rdfcore-wg@w3.org
> >>Subject: RE: Syntax-level typing (was Re: A data typing proposal)
> >>
> >>
> >>In my opinion, RDF literals have always had the
> >>property that if they look the same, they denote
> >>the same thing, and if they look different
> >>(modulo a few things like &#65; vs A),
> >>they denote different things.
> >>
> > 
> > Well, I don't see how that bears out in practice, in RDF
> > applications, which apply different interpretations to
> > the same literal string based on content.
> > 
> > 
> >>In my opinion, RDF has always had string literals and
> >>XML infoitem literals.
> >>
> > 
> > As I see it, literals in RDF were simply a way to capture
> > raw data that would be interpreted and utilized by higher
> > level applications, and has said *nothing* whatsoever about
> > the meaning or global consistency of meaning of such literal
> > strings. In fact, if you look at the examples in the original 
> > specs, it is fairly evident, IMO, that "Ora Lassila" is meant 
> > to denote the person, just as much as the blank node is meant to
> > denote him. Of course, not having a MT it is hard to argue
> > religiously about that, but I think that your view is not the
> > most obvious or most widely held.
> > 
> > Yes, your applications have presumed that literals constitute 
> > global constants, but that is not asserted by the majority of
> > applications that I am aware of, nor IMO by 
> > the RDF specifications.
> > 
> 
> 
> I think this reveals some of the problems you get into when 
> you define a 
> data model (as RDF is) without explicitly defining any operations, in 
> this case, some kind of equality test on literals.  Of course, you 
> (Patrick) are correct in saying "literals in RDF were simply a way to 
> capture raw data that would be interpreted and utilized by 
> higher level 
> applications", but I also think Dan's right.  Certainly the natural 
> assumption in my opinion is that, in RDF as it is (without 
> datatypes), 
> literals are of type string, and there is a "built-in" 
> equality test by 
> string comparison.  Of course, RDF applications know this, and hence 
> they know how to deal with the results of a string comparison in 
> determining whether <ex:age>10</ex:age> is equal to 
> <ex:weight>10</ex:weight> (or whether to use that comparison at all), 
> but that involves application semantics over and above what 
> is currently 
> built into RDF (just as RDF would determine that ex:age and ex:weight 
> weren't the same property, and an application might know that they 
> were).  What we are contemplating in the datatypes proposal 
> is whether 
> (and how) to change this situation.
> 
> --Frank
> 
> 
> 
> -- 
> Frank Manola                   The MITRE Corporation
> 202 Burlington Road, MS A345   Bedford, MA 01730-1420
> mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
> 
> 
> 
Received on Friday, 16 August 2002 10:08:21 EDT

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