RE: Proposed tweaks to Annotations

Hi!

I don't see any particular problem with your suggested approach to map additional FS vocabulary, such as SubAnnotationPropertyOf, to the existing RDF vocabulary, rdfs:subPropertyOf in this case. AFAICT, this would not really lead to a further semantic divergence between OWL 2 DL and OWL 2 Full. 

In OWL 2 Full (even in OWL Full), I can state subproperty axioms (or domain or range axioms) on annotation properties, anyway. The reason is that AnnotationProperties are also ObjectProperties in OWL Full. Hence, if someone writes an ontology in RDF having subproperty, domain or range axioms between annotation properties, then the author will receive the entailments, you mention below, from the OWL Full semantics. From an RDFS/OWL-Full perspective, this is /expected/ behavior, because annotation properties are properties in Full, not pure comments. This is the status quo, with or without the introduction of SubAnnotationPropertyOf.

The difference would be that, with the new FS vocabulary and its mapping to the existing RDF vocabulary, eventually certain RDF graphs would be accepted by OWL DL reasoners, which would nowadays be rejected as syntax errors. However, this would be a pure change in the /syntactic/ relationship between OWL 2 DL and OWL 2 Full: More RDF graphs, i.e. OWL 2 Full ontologies, would be accepted in OWL 2 DL. There would not be any difference in the semantic relationship, because all these subproperty, domain and range "axioms" on annotation properties would have no semantic consequences in OWL 2 DL.

I suggest that People, who are interested in having more RDF being accepted by OWL 2 DL, should consider this approach. This approach should mainly be discussed from an OWL 2 DL perspective, what advantages and disadvantages it will bring for DL. There won't be any consequences for OWL 2 Full, or for the semantic relationship between 2-DL and 2-Full (I don't see that it would hurt the correspondence theorem as is). 

Of course, if new /RDF/ vocabulary is being introduced instead, this /will/ have consequences for the Full semantics. But even then, I don't think that it will be a big problem for Full. This could be addressed by defining analog semantics for this new vocabulary as for the respective RDFS vocabulary, but restricted to the set "IOAP" of annotation properties. AFAICS, this would only enlarge the Full document a bit.

Michael

>-----Original Message-----
>From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org]
>On Behalf Of Boris Motik
>Sent: Friday, October 03, 2008 3:52 PM
>To: 'Alan Ruttenberg'; 'W3C OWL Working Group'
>Subject: RE: Proposed tweaks to Annotations
>
>
>Hello,
>
>I believe there are slight problems with both of these proposals.
>
>----------------------------------------------------------
>
>1. If we make owl:annotationSubPropertyOf a subproperty of
>rdfs:subPropertyOf, then we haven’t really achieved anything with adding
>owl:annotationSubPropertyOf, and we might as well save ourselves the
>trouble. Please let me explain.
>
>There is no problem with extending the structural specification of OWL 2
>with three new axiom types:
>
>- SubAnnotationPropertyOf
>- AnnotationPropertyDomain
>- AnnotationPropertyRange
>
>These could even be mapped into RDF using the existing OWL/RDF
>vocabulary. For example,
>
>(1) SubAnnotationPropertyOf( ap1 ap2 )
>
>could be mapped into the RDF triple
>
>(2) <ap1, rdfs:subPropertyOf, ap2>
>
>without any problems. The reason why this is so is declarations: to be
>able to use ap1 and ap2 in this axiom, both should be
>declared as annotations. Thus, we'll also have these triples:
>
>(3) <ap1, rdf:type, owl:AnnotationProperty>
>(4) <ap2, rdf:type, owl:AnnotationProperty>
>
>Now reverse-transformation is not difficult: by looking at the
>declarations, we know that we should translate (2) into (1).
>
>
>The problem with this approach is not in the RDF mapping, but in the
>difference in the semantics: in OWL 2 DL, we are completely
>ignoring the semantics of axioms such as (1), but this is not the case
>with OWL 2 Full. Consider the following example:
>
>(5) AnnotationPropertyDomain( ap C )
>(6) EntityAnnotation( NamedIndividual( i ) Annotation( ap "bla" ) )
>
>In OWL 2 DL, axioms (5)--(6) *do not* have any semantics, and they *do
>not* entail the following assertion:
>
>(7) ClassAssertion( C i )
>
>Now consider what happens in OWL Full. The translation of (5)--(6) into
>RDF is this:
>
>(8) <ap, rdfs:domain, C>
>(9) <i, ap, "bla">
>
>By the OWL Full semantics, the following triple is implied:
>
>(10) <i, rdf:type, C>
>
>Note that (10) corresponds to (7), but (7) is not entailed whereas (10)
>is. This is a problem: annotations bring OWL 2 DL and OWL 2
>Full further apart.
>
>
>Now the proposed change does not help: even if we convert (8) into
>
>(11) <ap, owl:annotationDomain, C>
>
>triple (10) is still entailed in OWL 2 Full if owl:annotationDomain is a
>subproperty of rdfs:domain. At the same time, (7) is still
>not entailed in OWL 2 DL. Thus, we haven't actually solved the problem.
>
>
>One possible solution to this problem would be *not to make* if
>owl:annotationDomain a subproperty of rdfs:domain in OWL 2 Full. In
>this way, (11) *would not* be entailed in OWL 2 Full, and this would
>match the situation in OWL 2 DL. (I understand that some people
>might not like this; that's why I'm saying "a possible solution".)
>
>Another solution is to decide that we don't care about this semantic
>divergence between the two languages. In that case, we don't
>need the new properties: as I explained, we can reverse-map everything
>without any problems.

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: Michael.Schneider@fzi.de
Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555

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