W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > January 2003

RE: Type of (the denotation of) a plain literal

From: Jan Grant <Jan.Grant@bristol.ac.uk>
Date: Thu, 16 Jan 2003 12:46:29 +0000 (GMT)
To: Graham Klyne <GK@NineByNine.org>
cc: Patrick.Stickler@nokia.com, w3c-rdfcore-wg <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.GSO.4.44.0301161236230.28405-100000@mail.ilrt.bris.ac.uk>

On Thu, 16 Jan 2003, Graham Klyne wrote:

>
> Patrick,
>
> >What you're really asking is "can we do untidy, implicit datatyping"
> >and the answer is a big loud NO (regretably).
>
> I think you're misunderstanding my point, which is certainly *not* about
> doing untidy implicit datatyping.  We've done that one to death
> already.  Note that my test cases were about *satisfiability*, not
> *entailment*.

> > > (1)  Is the following satisfiable?
> > >
> > >     ex:prop rdfs:range xsd:string .
> > >     ex:subj ex:prop "abc" .
> >
> >No. An rdfs:range assertion specifying a datatype "excludes"
> >all plain literal values, because the semantics of those
> >plain literals is fixed and there is no implicit datatyping
> >in RDF.

From CONCEPTS:

	A plain literal is a string combined with an optional language
	identifier.

which can be read ambiguously. Either as,

	... is a string optionally combined with a language identifier
	(ie, a plain literal is from { x | x a string } union
	{ (x, y) | x a string & y a language identifier }

or as,

	... is from { (x, y) | x a string & y a language identifier
		or "the null language identifier" }


If you read it as the former, and you're asking questions about
RDFS+D(xsd:string)-satisfiability, and if you have a classic
set-theoretic intuition about the equality of character sequences (ie,
no intension or type tag as "part" of the denoted value), then it would
appear that the answer to your test case is, "yes".

> > > (2)  Is the following satisfiable?
> > >
> > >     ex:prop rdfs:range xsd:string .
> > >     ex:subj ex:prop "abc"@en .

No, using either reading of the definition of a literal in CONCEPTS.

Following the link, section 6.5 of CONCEPTS would seem to support the
first reading of that sentence. So your question of satisfiability has
then to be answered by looking at your definition (and XSD's defintion)
of a "string", that is, a "character sequence".


-- 
jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/
(ECHOY GRUNTING) (EERIE WHISPERS) aren't subtitles great?
Received on Thursday, 16 January 2003 07:48:06 EST

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:55:21 EDT