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OWL S&AS comment - owl:Ontology mapping to/from RDF triples

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Fri, 09 May 2003 19:28:49 +0100
To: public-webont-comments@w3.org
Message-ID: <10482.1052504929@hoth.ilrt.bris.ac.uk>


  OWL Web Ontology Language Semantics and Abstract Syntax
  W3C Working Draft 31 March 2003
  http://www.w3.org/TR/2003/WD-owl-semantics-20030331/


Firstly a probably editorial thing - what is an OWL Ontology?  In the
abstract syntax it is defined as an

  [[ 2.1. Ontologies

  An OWL ontology in the abstract syntax contains a sequence of
  axioms and facts.

  ...
    ontology ::= 'Ontology(' [ ontologyID ] { directive } ')'
    directive ::= 'Annotation(' ontologyPropertyID ontologyID ')'
	          | 'Annotation(' annotationPropertyID URIreference ')'
                  | 'Annotation(' annotationPropertyID dataLiteral ')'
                  | 'Annotation(' annotationPropertyID individual ')'
                  | axiom
                  | fact
  ]]
  -- http://www.w3.org/TR/2003/WD-owl-semantics-20030331/syntax.html#2.1

So the definition is rather:
   1) a named container 
   2) contains a sequence of (axioms OR annotations OR fact)

Annotations seem to be missing from the wording.


The more substantive issue is on the mapping of the abstract syntax
above to RDF triples:
  [[
    Abstract Syntax (and sequences)
       Ontology(O directive1 ... directiven)

    Transformation
       O rdf:type owl:Ontology .
       T(directive1) ... T(directiven)

    Abstract Syntax (and sequences)
       Ontology(directive1 ... directiven)

    Transformation
       O rdf:type owl:Ontology .
       T(directive1) ... T(directiven)
  ]]  --  http://www.w3.org/TR/2003/WD-owl-semantics-20030331/mapping.html#4.1

These omit both the sequence and the relationship to the contained
items.  The mappings for Annotation() may make a connection to the
OntologyID but it is not clear that any of the axioms do.  This
information thus seems to be lost.

The second transformation T(S) seems to have a bug.  There is no 'O'
in the Abstract Syntax of the second abstract syntax.

  Aside: it would help me if these transformations had had anchors
  and/or numbers.

If several OWL Ontologies are in the same RDF graph such as when they
are taken from multiple sources (such as via owl:import), there will
be no connection between the OWL Ontology and the components.

  Aside: I found one OWL instance schema that used rdf:isDefinedBy,
  one of the built in annotations, to perform this at:
    http://www.aktors.org/ontology/extension
  But this has no additional OWL semantics.

Please can you explain why the OWL Ontology container-to-component
relation in the abstract syntax is not passed through to the OWL
transfer syntax.

Thanks

Dave
Received on Friday, 9 May 2003 14:30:23 GMT

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