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Re: Annotations cause RDF axioms to disappear?

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Sat, 26 Jul 2008 20:05:33 +0100
Message-Id: <07DBBB8C-5010-4A6F-B996-AC2133160586@cs.man.ac.uk>
Cc: "public-owl-comments@w3.org" <public-owl-comments@w3.org>
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>


Annotation of axioms is an important new feature in OWL 2. When  
mapping annotated axioms to RDF, the annotation needs to be attached  
to a triple. In order to do this, the triple is reified.

There is currently a discussion in the OWL Working Group as to  
whether, for annotated axioms, the mapping should be changed to  
generate *both* the "base triple" (s p o) and the reified (and  
annotated) version. Would this solve your problem? I can't guarantee  
that this will come to pass, because "duplicating" the triple also  
has it's drawbacks, but knowing your position would be useful input  
to the debate.


On 22 Jul 2008, at 03:03, Booth, David (HP Software - Boston) wrote:

> Section 3 of OWL 2 Web Ontology Language: Structural Specification  
> and Functional-Style Syntax says:
> http://www.w3.org/TR/2008/WD-owl2-syntax-20080411/#Ontologies
> [[
> OWL 2 allows each axiom to contain annotations. These can be used  
> to associate arbitrary information with an axiom. This information  
> does not affect the semantics of the language in any way.
> ]]
> But Section 2.1 of OWL 2 Web Ontology Language: Mapping to RDF  
> Graphs says:
> http://www.w3.org/TR/2008/WD-owl2-mapping-to-rdf-20080411/ 
> #Annotated_Axioms
> [[
> Axioms with annotations are reified. If s p o is the RDF  
> serialization of the corresponding axiom without annotations given  
> in Table 2 and the axiom contains annotations Annotation(apIDi  
> cti), 1  i  n, then, instead of being serialized as s p o, the  
> axiom is serialized as follows . . . .
> ]]
> In other words, from a strictly OWL 2 perspective, the reified  
> axioms (apparently) still carry the same semantics as the non- 
> reified axioms.  However, from an RDF perspective there is an  
> enormous difference: an annotation causes the axioms to disappear!   
> Given that the axioms are usually the main point of OWL/RDF  
> statements -- though of course this is a subjective -- it seems  
> quite unfortunate that they disappear by the mere addition of an  
> annotation.
> Have I understood this correctly?  If so, this looks to me like it  
> would be a significant problem in making OWL 2 work well with other  
> RDF, as RDF is combined from multiple sources, some of which might  
> have orginally been OWL 2.
> David Booth, Ph.D.
> HP Software
> +1 617 629 8881 office  |  dbooth@hp.com
> http://www.hp.com/go/software
> Statements made herein represent the views of the author and do not  
> necessarily represent the official views of HP unless explicitly so  
> stated.
Received on Saturday, 26 July 2008 19:06:38 UTC

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