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Re: test case A and superProperty

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 02 Jul 2002 10:55:07 +0300
To: ext Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>, Pat Hayes <phayes@ai.uwf.edu>
Message-ID: <B947370B.17B82%patrick.stickler@nokia.com>

On 2002-07-01 20:55, "ext Brian McBride" <bwm@hplb.hpl.hp.com> wrote:

> As per my recent posts (sorry for the shotgun effect, I wanted to keep the
> threads separate), its been suggested that we can have test case A be yes
> and test case C be no.
> I just wanted to note that there is an interaction between this test case
> and rdfs:subPropertyOf.  Consider:
>  _:a dc:title "4th July" .
>  _:b dc:date  "4th July" .
> [I don't know DC well enough to know whether this is a realistic example, I
> suspect not so consider this just illustrative]
> All is reasonably well.  With appropriate datatype range constraints one of
> these denotes a string and the other a date.
> Now add a common super property for all the dc properties:
>  dc:property rdf:type        rdf:Property .
>  dc:title rdfs:subPropertyOf dc:property .
>  dc:date  rdfs:subPropertyOf dc:property .
> This now entails:
>  _:a dc:property _:l .
>  _:b dc:property _:l .
> I assume this is still monotonic, since I haven't actually retracted
> anything, though it sure feels like changing my mind to me.

This is an additional example of why a property alone cannot
clarify whether two string-equal literals denote the same thing.

This touches upon the "BOOM" examples I provided many months
ago regarding the relationship between datatyping, rdfs:subPropertyOf,
and query engine bindings. One cannot divorce a globally datatyped
value from the original statement context within which it was
expressed, because then, the proper context for correct interpretation
is lost.

Thus, while it is true that, given the above subproperty relations
that a value of either dc:title or dc:date is also a valid value of
dc:property, that does not mean that all literal values of dc:property
that are string equal denote the same thing.

> A more extreme form is to postulate the existence of a common super
> property of all properties, which we have talked about in the past.  If
> there were such a thing and the answer to A is yes, then we'd have tidy
> literals anyway.

Right. If we choose untidy literals, the answer to A cannot be yes.


             A     B     C     D
Tidy         Y     Y     Y     N
Untidy       N     N     N     Y

> At this point I think I need to hear Pat say, "relax".

Relax.  (yeah, I know you meant the *other* Pat ;-)


Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Tuesday, 2 July 2002 03:55:08 UTC

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