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Re: RDF Datatyping Working Draft

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 04 Apr 2002 08:17:35 +0300
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <B8D1BC9F.126DC%patrick.stickler@nokia.com>
On 2002-04-03 14:27, "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com> wrote:

> Looks like a promising start ...
> I feel that your pictures can help me clarify my objection:
> Section 6.1.2 RDF Model Theory Interpretation
> http://www-nrc.nokia.com/sw/RDFDatatyping.html#ntoc_26
> and
> Section 6.1.3 RDF Datatyping Interpretation
> http://www-nrc.nokia.com/sw/RDFDatatyping.html#ntoc_27
> are different.
> In 6.1.3 all the properties have the same values (satisfying "Jeremy's
> entailment"). In 6.1.2 they don't.
> Now, if we leave it at that, and have no model theory for datatypes, then
> that seems fair enough, and much of my objection is satisfied. But if the
> model theory addresses half of datatyping but another half lies somewhere
> else it feels very unclear as to when one should use a model theoretic
> interpretation and when one should use a datatyping interpretation.

This is a valid question, and one that probably should be addressed
in some fashion by the Datatyping rec.

> It also feels dubious that the relationship between model theoretic
> interpretations and datatyping interpretations is non-monotonic. (And that
> this non-monotonicity seems to be motivated primarily by the desire for tidy
> literals - my valuation is that non-monotonicity is a greater evil than
> either tidiness or untidiness).

Perhaps my illustrations are a bit misleading, by using 'ex:age = ...'
as annotations rather than new assertions.

I don't really see any non-monotonicity there, in
that the meaning of the literal nodes does not change. Perhaps
the following would be clearer with regards to the datatyping
interpretation, using implications which expand the implicit
knowledge in the idioms to the explicit datatyping interpretation:

   ex:age rdfd:range xsd:integer .
   John ex:age [ xsd:integer "25" ].
   Jane ex:age "25" .
   Judy ex:age [ rdfd:lex "25" ].
   John ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
   Jane ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
   Judy ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
} .

Forgive the use of the URVs, but they do capture the
datatyped literals very nicely, and in a tidy manner ;-)

C.f. http://ietf.org/internet-drafts/draft-pstickler-val-00.txt

Thus, the datatyping interpretation of the inline idiom does
not change the MT interpretation of the literal node which
is the direct value of the ex:age property, but adds new
knowledge based on the combination of the rdfd:range and
the inline idiom. Is that really then non-monotonic? The
meaning of the literal node "25" does not change. It still
denotes the literal string. And the value of ex:age in the inline
idiom does not change. It is still the literal node "25". We have
simply inferred a new statement based on the combination of
the inline idiom and the rdfd:range which ascribes more
explicit, localized knowledge about Jane's age.

Now then, if we presume a version of N3/CWM which has native support
for XML Schema datatypes (or at least for xsd:integer) we could
express the extra-RDF application interpretation as

   John ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
   Jane ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
   Judy ex:age <val:(http://www.w3.org/2001/XMLSchema%23integer)25> .
   John ex:age 25 .
   Jane ex:age 25 .
   Judy ex:age 25 .
} .

Again, the meaning of the datatyped literal pairing statements
does not change, but rather, new (more explicit) statements are
inferred based on additional knowledge -- in this case, knowledge
about the actual datatype mapping for xsd:integer.



Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Thursday, 4 April 2002 00:15:08 UTC

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