W3C home > Mailing lists > Public > www-rdf-interest@w3.org > September 2001

RE: Literals (Re: model theory for RDF/S)

From: <Patrick.Stickler@nokia.com>
Date: Thu, 27 Sep 2001 14:20:25 +0300
Message-ID: <2BF0AD29BC31FE46B78877321144043114BFEA@trebe003.NOE.Nokia.com>
To: champin@bat710.univ-lyon1.fr, www-rdf-interest@w3.org, www-rdf-logic@w3.org


> -----Original Message-----
> From: ext Pierre-Antoine CHAMPIN [mailto:champin@bat710.univ-lyon1.fr]
> Sent: 27 September, 2001 12:03
> To: www-rdf-interest@w3.org; www-rdf-logic@w3.org
> Subject: Literals (Re: model theory for RDF/S)
> 
> 
> Sorry to bring back an old debate, probably set up for everyone except
> me, but their in curently another debate on rdf-logic about the model
> theory, and the special case of literals make it quite complicated.
> 
> So I ask: given the existence of a quite convinient URI 
> scheme 'data:',
> is the Literal/Resource disctinction still necessary in RDF?
> 
> Couldn't we consider that any literal in the syntax should be 
> converted
> by the parser into a 'data:' URI? This does not need to alter the
> syntax, and then keeps compatibility with existing RDF bits.

I've been leaning towards this sort of view for awhile now. I
also agree that it would make the conceptual model more consistent.
 
> Furthermore, this would offer a straightforward solution to some
> problems like expressing the xml:lang attribute in RDF.

I don't think actually that it would provide a solution for
that per se, as xml:lang is a property of the occurrence, not
the literal. E.g. the literal byte sequence "pan" could be
either English or Spanish (and possibly other languages as well)
yet I would presume that <... xml:lang="en">pan</...> is
a statement about the particular occurrence of the literal and
not about the byte sequence "pan" in general. You wouldn't
(I don't think) want to have multiple statements attributing
multiple languges to a given string -- at least insofar as
the intended use of xml:lang is concerned, right?

I would myself love to see a data type URI approach by which 
otherwise "literal" values could be defined as instances of a 
given data type URI. E.g.

   dt:integer:5
   dt:token:en
   dt:date:2001-09-27
   dt:time:2000-11-01T17:32:20Z
   dt:float:38829.11883292
   ...

etc.

Then, one can associate the syntax and semantics of the particular
data types using RDF. 

Furthermore, one could say things about the data type scheme like

   <rdf:Description rdf:about="dt:date">
      <rdfs:isDefinedBy rdf:resource="http://www.w3.org/TR/NOTE-datetime"/>
      <rdfs:seeAlso
rdf:resource="http://www.iso.ch/iso/en/CatalogueDetailPage.CatalogueDetail?C
SNUMBER=26780"/>
 
<dt:pattern>[0-9]{4}-((0[1-9])|(1[012]))-((0[1-9])|([12](0-9))|(3[01]))</dt:
pattern>
      <rdf:type rdf:resource="http://purl.org/dc/terms/W3CDTF"/>   
   </rdf:Description>

etc.

All the info you need to constrain property ranges, perform validation
of input values, and what not. (Note that the URI scheme is combined
with a namespace for defining properties of namespaces (instances) of 
that scheme).

Eh?

Cheers,

Patrick

--
Patrick Stickler                      Phone:  +358 3 356 0209
Senior Research Scientist             Mobile: +358 50 483 9453
Nokia Research Center                 Fax:    +358 7180 35409
Visiokatu 1, 33720 Tampere, Finland   Email:  patrick.stickler@nokia.com
 
Received on Thursday, 27 September 2001 07:20:40 GMT

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