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Re: draft question: option C

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Thu, 17 Oct 2002 15:38:05 +0100
Message-Id: <>
To: Dan Connolly <connolly@w3.org>
Cc: Brian McBride <bwm@hplb.hpl.hp.com>, Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org


It is my recollection that the idea of datatype URIs being both classes and 
properties has been floating around for some time [*], and this is the 
first time I've been aware of dissent with it (not counting the message to 
rdf-logic as a record of dissent).

I think datatype as class and properties represent current WG thinking, so 
if there is a problem with this I think we should hear what that problem is.

[*] a recent reference is: 

and from the datatyping draft that was agreed would be the basis for work 
going forward:
4. RDF Datatyping Model Theory

The RDF Model Theory explains the fundamental model-theoretic concepts like 
interpretation, universe, extension etc. used for interpreting the 
semantics of RDF graphs. This section assumes familiarity with these basic 

Suppose I is an RDF interpretation of a graph E. Then I is datatyped (with 
respect to a set D of datatypes) if the following is true for any datatype 
URI Reference ddd (with I(ddd) in D):

(1) ICEXT(I(ddd)) = {x : <x,y> in IEXT(I(ddd))}

I.e. the class extension of the datatype class is the value space of the 

(2) For any typed literal ddd"LLL",   I(ddd"LLL") = L2V(I(ddd))("LLL")

I.e. the typed literal node denotes the datatype value having the lexical 
representation "LLL" according to the lexical to value mapping defined for 
the datatype ddd

Condition (1) is quite explicit about this.
The same appeared in some of Pat's earlier documents on this subject.


At 08:38 PM 10/16/02 -0500, Dan Connolly wrote:

>On Wed, 2002-10-16 at 14:16, Brian McBride wrote:
> > At 10:25 15/10/2002 -0500, pat hayes wrote:
> >
> > [...]
> >
> > >>I want to be sure that whatever spec we come up with,
> > >>I can continue to use the datatype property idiom...
> > >>     <k:Thursday r:about="#_thu10">
> > >>         <dt:date>2002-10-10</dt:date>
> > >>     </k:Thursday>
> > >>         -- http://www.w3.org/2002/10dc-uk/itin3.rdf
> > >>
> > >>So far, our (published WD) specs have been consistent
> > >>with a view that classes and properties are disjoint. (In
> > >>SWAD, we use that assumption for lint-style checking.)
> > >>The 6Sep decision seems to conflict with the
> > >>use of the datatype property idioim under
> > >>the disjointness-of-properties-and-classes
> > >>assumption.
> > >
> > >I was not aware that there was any such assumption. On the contrary, in
> > >fact: the MT has been designed to allow the possibility of a class and a
> > >property being the same. If this is an assumption, maybe we should 
> reflect
> > >it formally in the language. Certainly that would make the Webont work a
> > >little simpler.
> >
> > We discussed this.  It was felt that asking users to distinguish between
> > two uri's for a datatype, one for the class and one for the property would
> > be unnecessarily confusing.
>Er... it was also felt that confusing the value space with
>the mapping is unnecessarily confusing; I'm not sure if that's
>part of the discussion you're talking about, since you
>don't give a citation, but it is a matter of record:
>" The proposal treats datatypes as if they were the classes which
>     conventionally have the same name (eg "integer"), but according to
>     the XMLSchema spec, they are not."
>-- http://lists.w3.org/Archives/Public/www-rdf-logic/2001Feb/0091.html
> > The notion that classes and properties were not disjoint has been around
> > for many months
>Which notion, exactly? I see two:
>         (a) the RDF specs don't guarantee that
>         classes are disjoint from properties
>         (b) the RDF specs guarantee that
>         classes and properties intersect.
>(a) has been around for a while; (b) has been with us only
>since 6 Sep.
>Even in situation (a), some folks can advocate
>"keep your properties separate from your classes"
>as a best practice (sorta like ala # vs /) while the spec
>remains silent on the issue.
>With the WG proposing (b), it forces those
>of us who advocate keeping properties and
>classes separate to object.
> > and has found general acceptance.
>I don't think (b) has found general acceptance.
>It hasn't found acceptance among the developers
>I work with.
> >  I'm not convinced that
> > SWAD's lint application is sufficiently strong justification to reopen 
> this.
>Well, perhaps it's not worth re-opening the issue at this
>point; we're clearly not going to make everybody happy with
>any datatypes design.
>But I couldn't let your "everybody thinks this is just fine"
>go unqualified.
>I'm not sure I'm going to be able to get this design thru
>last call without objections from the folks I work with.
>Dan Connolly, W3C http://www.w3.org/People/Connolly/

Graham Klyne
Received on Thursday, 17 October 2002 10:34:22 UTC

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