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Re: Mapping to RDF Graphs and reification

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Thu, 4 Dec 2008 09:11:55 +0000
Message-Id: <692B7FE9-D7F7-4407-9590-EEF267A0002A@cs.man.ac.uk>
Cc: Owl Dev <public-owl-dev@w3.org>
To: Jeff Thompson <jeff@thefirst.org>

On Dec 4, 2008, at 2:55 AM, Jeff Thompson wrote:

> Thanks everyone for the comments.  Note that the message from Tim I  
> quoted was
> about provenance.
> http://lists.w3.org/Archives/Public/semantic-web/2007Jan/0088.html
> This issue is confusing because a first instinct for annotations is  
> to use them
> to give the provenance of a triple.

In OWL, we focus on Axioms, but the point remains.

>   Indeed the first annotation example in
> the OWL 2 primer appears to be

does address.

> 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

It definitely is provenance data.

> about who is being quoted

It is not a quotation. I definitely wouldn't conflate the two notions.

> to say that f:John f:hasWife f:Mary, but rather an assertion that  
> peter put

I.e., the provenance of that axiom.

> 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.

Annotations are not about quoting, for sure.

>   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.

I don't know what you mean by "absorb", but I suspect that it's not  
quite as true as you'd like. Annotations do not follow entailments.

> 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.

They solve a great deal of provenance issues people have (like  
tracking who did what to which axiom) in building ontologies. They do  
not, nor are they meant, to deal with quotation. However, they can be  
used for things like tracking down whether it was two separate people  
who added contradictory axioms, which of the contradictory axioms  
came first, etc. You don't need (or want) quotation for that.

> 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?

I would need a much more convincing account that there is a problem  
before adding such a warning to the primer, where is such a thing is  
likely to go. I will have a discussion of annotations, so when that's  
done you might check to see if it meets your concerns.

But it's just false to say, "Annotations are not appropriate for  
provenance data". They are. They do not, and it's very hard to see  
how they would suggest, quote. They *annotate* existing axioms.

We also use "reification" like vocabulary to encode negation.

Received on Thursday, 4 December 2008 09:12:22 UTC

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