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Re: Mapping to RDF Graphs and reification

From: Jeff Thompson <jeff@thefirst.org>
Date: Wed, 03 Dec 2008 18:55:21 -0800
Message-ID: <49374699.6090000@thefirst.org>
To: Pat Hayes <phayes@ihmc.us>
CC: Bijan Parsia <bparsia@cs.man.ac.uk>, public-owl-dev@w3.org

Pat Hayes wrote:
> The main split (there are others less important) is between thinking of 
> reification as a kind of quotation, a meta-theoretic description of the 
> /syntax/ of the reified triple - what Tim has always had in mind, I 
> believe - and thinking of it instead as a description of what the 
> reified triple is asserting about the world, basically of the 
> /proposition/ expressed by the triple.  Do you want the three objects in 
> the reification to denote the /symbols/ of the original triple, or the 
> /things/ that those symbols denote?  

Thanks everyone for the comments.  Note that the message from Tim I quoted was
about provenance.
This issue is confusing because a first instinct for annotations is to use them
to give the provenance of a triple.  Indeed the first annotation example in
the OWL 2 primer appears to be addressing this:

Individual f:John
   Facts: Annotations: dc:author Individual(f:peter)
                       dc:creationDate "2008-01-10"^^xsd:date
                       rdfs:comment "A simple fact about John"
   f:hasWife f:Mary

The confusion is that this is arguably NOT provenance data about who is being quoted
to say that f:John f:hasWife f:Mary, but rather an assertion that peter put this
triple into THIS ontology according to the semantics that peter knew that
this ontology has for f:John, etc.  This is OK, and within the intended semantics
of OWL 2 annotations.

If however there is someone else, such as Bob, out there in the world who is the
provenance source and is being quoted as saying that John hasWife Mary, then it
matters to quote how Bob said this.  If the ontology includes f:Mary sameAs f:SecretAgent99,
then Bob may never have said that John hasWife SecretAgent99, so it is not correct
to use an OWL 2 style annotation to *quote* what Bob originally said, because the
semantics of OWL 2 annotations absorb all the sameAs and other inferences in the ontology.

The problem is that many people will see OWL 2 annotations and leap on them to solve
the desperate need for provenance data in RDF/OWL, but they shouldn't.

So to my question: Is it worth my time to try to convince public-owl-comments@w3.org
that some words of warning should be added to the specification?

- Jeff
Received on Thursday, 4 December 2008 02:56:00 UTC

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