W3C home > Mailing lists > Public > www-archive@w3.org > December 2001

Re: UPDATE: datatypes

From: Dan Connolly <connolly@w3.org>
Date: 17 Dec 2001 15:07:32 -0600
To: "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>
Cc: www-archive@w3.org, fps@research.bell-labs.com, phayes@ai.uwf.edu, jjc@hplb.hpl.hp.com, Frank.van.Harmelen@cs.vu.nl, horrocks@cs.man.ac.uk, mdean@bbn.com, lynn.stein@olin.edup
Message-Id: <1008623254.4219.75.camel@shoal>
On Mon, 2001-12-17 at 12:46, Peter F. Patel-Schneider wrote:
> From: Dan Connolly <connolly@w3.org>
> Subject: Re: UPDATE: datatypes
> Date: 17 Dec 2001 11:35:57 -0600
> 
> > On Mon, 2001-12-17 at 11:19, Peter F. Patel-Schneider wrote:
> > > 		Datatypes in SWOL
> > > 
> > > 	Peter F. Patel-Schneider
> > > 	Bell Labs Research
> > > 	(17 December 2001)
> > > 
> > > 
> > > The semantics and syntax documents that I sent out contain a treatment of
> > > datatypes that has the following features.
> > > 
> > > 1/ Local datatyping syntax (and verification) can be handled by XML Schema
> > >    verification.  In particular,
> > >    
> > >    <Person rdf:about="John">
> > >      <age xsi:type="xsd:int">10</age>
> > >    </Person>
> > > 
> > >    results in the age of John being the integer 10.
> > 
> > Where is the specification of that syntax?
> 
> XML Schema Part 1: Structures, http://www.w3.org/TR/xmlschema-0/, Section
> 2.6.1 xsi:type, is, I believe, the primary specification of that syntax.
> The syntax is used extensively in the XML Schema documents, including XML
> Schema Part 0: Primer, http://www.w3.org/TR/xmlschema-0/, and, XML Schema
> Part 2: Datatypes, http://www.w3.org/TR/xmlschema-2/.

Hmm... I'm familiar with that document, but I don't quite
see how it applies; I don't see what shema is to be used
for <Person>, rdf:about, etc.

Perhaps it's explained elsewhere...

> > It doesn't mean what you suggest it means when parsed as RDF.
> 
> I'm not saying that it does mean *anything* as parsed by a current RDF/XML
> parsed.  I'm saying that it does mean something in
> 
> 	``The semantics and syntax documents that I sent out''

It's traditional to cite sources by URI.

I presume you mean this one:
http://lists.w3.org/Archives/Public/www-webont-wg/2001Dec/att-0123/02-syntax-data-model.text

which, in turn, cites

XQuery 1.0 and XPath 2.0 Data Model (W3C Working Draft 7 June 2001)
http://www.w3.org/TR/2001/WD-query-datamodel-2001-6-7/

I haven't read them in detail, but from a quick scan,
it seems to suggest that all of XML Schema becomes
necessary to parse this language. That doesn't seem
cost-effective.

RDF syntax is constrained so that consumers can
parse it without a schema. This (a) simplifies
implementations and (b) avoids a lot of trust
issues (do I have the right schema?) but
at the cost of (c) the syntax is somewhat awkwardly
constrained.

If we're willing to bite the bullet on
(a) and (b), we might as well get something
prettier (c) while we're at it.


> 
> [...]
> 
> > > 1/ Determine if you disagree with the following:
> > >    - The above is a reasonable way of handling datatypes in SWOL.
> > 
> > nope; it's very much more complex, syntacitcally and
> > in the model theory, than other alternatives
> > under discussion in the RDF Core WG.
> 
> Objection noted.
> 
> The proposal in my documents is more semantically complex than others
> simply because it handles data values that do not have a locally-specified
> lexical-to-value mapping.  If one were to move to an environment where this
> mapping either had to be locally given for all literals or where the
> mapping was unambiguous overal then there would be little difference in the
> semantic complexity.


Hmm... I don't think I understand that. What does
"locally specified lexical-to-value mapping" mean?


> > >    - The above does not introduce other problems.
> > > 
> > > 2 (optional)/ Make suggestions for improvements.
> > 
> > See Melnick's work in the RDF Core WG:
> >  http://www-db.stanford.edu/~melnik/rdf/datatyping/
> 
> I take it that you are advocating datatyping scheme ``S''.  
> 
> I have serious reservations about ``S'', mostly concerning compatibility
> with existing RDF usage and with XML documents.

Yes, we've talked about that; see the recent discussions and
refinenments, in particular Idiom B ("backward compatible")
under 4.9 Modeling styles.

> If the RDF Core WG has not made a decision by the time of our face-to-face, 
> it might be fruitful for us to spend some time on this issue there.

yup.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 17 December 2001 16:08:58 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 7 November 2012 14:17:15 GMT