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Re: Axiom annotations

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Wed, 18 Apr 2007 21:55:38 +0100
Message-Id: <FBEF941A-157A-44BC-816D-7D4D260D8A5B@cs.man.ac.uk>
Cc: public-owl-dev@w3.org
To: Michael Schneider <m_schnei@gmx.de>

On Apr 18, 2007, at 9:36 PM, Michael Schneider wrote:
[snip]

> If I correctly understand Alan's above citation from the draft,  
> this is meant as an "EITHER s p o OR reification" (whatever form of  
> reification will be used in the end).
>
> So, if I take my old but beloved OWL1.0 compliant ontology, which  
> is serialized in RDF, and then cautiously start to add a few  
> comments to all its axioms, I would not recognize the original RDF  
> anymore, because all those s p o statements representing the axioms  
> would now have been replaced by ugly and fat reifications? So still  
> exactly the same ontology (annotation have no semantic  
> implications, right?),

It's not exactly the same ontology: it is semantically *equivalent*  
under the OWL 1.1 semantics, but now some axioms have annotations on  
them. There is definitely more information in the ontology and we  
need some way to express that.

Note that such annotations might be used by tools in quite  
significant ways, whether as language extensions or by tools. One  
simple example is storing providence information for an axiom in an  
annotation and using that to help guide inconsistency resolution in a  
repair tool.

I think someone using a repair tool in this way would notice quite a  
lot of difference between the annotationed and the annotationless  
ontology.

This, of course, independent of the horrowshow trying to get these  
into RDF that we've been facing.

Note that this is true for negated assertions as well, which is  
rather a more horrible circumstance, I think.

> but now with a largely different serialization. I would not like this!
>
> Really, I would prefer to have a "ALWAYS s p o AND ADDITIONALLY  
> reification IF NEEDED FOR ANNOTATION".

This is possible but a bit dangerous. There is no connection between  
the reification and the regular, thus it's possible for them to get  
out of synch. If they do get out of synch, how do you know that your  
annotation is annotating *that* axiom?

> This would be more conservative,

In some sense.

> even my old OWL1.0 parser would recognize this ontology,

But your editor might screw up such ontologies *very* easily.

(BTW, which OWL 1.0 parser are you using/do you maintain?)

> because it would simply ignore the additional reification.
>
> The drawback would of course be that there would be one more  
> statement within the serialization of an annotated axiom.

The drawback is what I mentioned above. Tools would have to be revved  
anyway and editing by hand, well, I would have to edit *both forms  
anyway*. Yeek.

(There is no *good* solution here within the current standard  
features of RDF as I think we all know :()

> But I could live with this easily: Reification adds four statements  
> plus one for the annotation, so enlargement would be (at most) 20%.  
> And specifically, RDF/XML provides me with a nice syntactic trick  
> to get reification from an existing triple, by adding an 'rdf:ID'  
> attribute to the predicate property, see
>
>   http://www.w3.org/TR/rdf-primer/#example20
>
> So my XML serialization would be even /smaller/ in comparison with  
> reification without the s p o triple included.

Uhm....how is this smaller than just having the reified one using the  
syntactic trick? I'm missing something.

I think if you are going to make heavy use of axiom annotations, you  
may prefer to stick with the XML syntax.  You could always strip them  
out when conneging with older tools. That's my plan.

Cheers,
Bijan.
Received on Wednesday, 18 April 2007 20:55:43 GMT

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