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Re: ACTION-268

From: Christine Golbreich <cgolbrei@gmail.com>
Date: Thu, 22 Jan 2009 00:00:54 +0100
Message-ID: <b0ed1d660901211500q1a7f31acl9b27b14abf2184e4@mail.gmail.com>
To: W3C OWL Working Group <public-owl-wg@w3.org>
Regarding documentation  related to JH1 :

1) I can see that Boris had already extensively documented the 'named' issue
in the Syntax and added an example of non inference with no named instance.
The sentence below might be merged/moved to it.

2)
- the NF&R has already asserted  that a  haskey axiom only concerns named
instances of a class C as well:
"A HasKey axiom states that each *named* instance of a class is uniquely
identified by a (data or object) property or a set of properties"
 - The example also stresses that a haskey axiom does not state that each
instance of the class C has at least one value for the key property
- As proposed at last TC, I have now extended the comment of the example in
adding the sentence "The inference that each patient who has a *
a:hasWaitingListN* belongs to the class *a:RegisteredPatient* cannot be
drawn "
so as to make it clear that the inference of belonging to the class cannot
be drawn, which was, if I remember correctly, the initial point of the
discussion.

3) Moreover there is also an addition done by Michael  in RDF-Based Sem. in
section 5.14

" <http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#tab-semcond-keys>Keys
provide an alternative to inverse functional properties (see Table
5.13<http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#tab-semcond-propertycharacteristics>).
They allow for defining a property as a key local to a given class: the
specified property will have the features of a key only for individuals
within the class, and no assumption is made about individuals external to
the class, or for which it is unknown whether they are instances of the
class. Further, it is possible to define "compound keys", i.e. several
properties can be combined into a single key applicable to composite
values."


Christine

2009/1/21 Bijan Parsia <bparsia@cs.man.ac.uk>

>
> Done with:
>         http://www.w3.org/2007/OWL/wiki/index.php?title=Syntax&oldid=17348[Bijan Parsia]
>
> To:
>        http://www.w3.org/2007/OWL/wiki/Syntax#Keys
>
> I added the second sentence:
>        """A key axiom of the form HasKey( owl:Thing OPE ) is similar to the
> axiom InverseFunctionalProperty( OPE ); the main difference is that the
> first axiom is applicable only to individuals that are explicitly named in
> an ontology, while the second axiom is also applicable to individuals whose
> existence is implied by existential quantification. Another, more minor,
> difference is that while inverse-functional property is inverse-functional
> for all assertions using that property, keys can be scoped to assertions
> involving individuals of a certain class."""
>
> Cheers,
> Bijan.
>
>
>


-- 
Christine
Received on Wednesday, 21 January 2009 23:01:29 GMT

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