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RDFTM.HandlingOccurrencesr1.5 - 24 Oct 2005 - 16:44 - ValentinaPresuttitopic end

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Occurrences

Valentina
The classes and properties involved in the guidance for occurrences are the followings:

  • rdftm:OccurrenceProperty which is defined as rdfs:subpropertyOf rdf:Property. Furthermore, for OWL-DL compliance it is defined as rdfs:subClassOf owl:ObjectProperty.
Topic Maps defines an occurrence as a special type of association. Occurences can be internal and external. An occurence is a bynary association between a subject and an information resource. In particular, the value of an internal occurrence is a string and can have a datatype that is not a URI. If the datatype is a URI then the occurrence is external. Occurrences bacome RDF properties. RDF does not have the concept of occurrence, so the problem is to to decide if a RDF property has to be treated either as a Topic Maps association or a Topic Maps occurrence.

TM2RDF

  • Internal occurrences become RDF properties.
  • External occurrences become RDF properties and the occurrence is typed as rdftm:OccurrenceProperty

RDF2TM

  • If there is not guidance leading to interpretation as names or identifiers:
    • !RDF properties which value is a literal are translated to Topic Maps internal occurrences
    • RDF properties which value has a datatype, which is not a URI are transalted to internal occurrences
  • RDF properties which are intances of rdftm:OccurrenceProperty are translated to external occurrences

Backup

Nicola

Topic Maps uses the element to assign an occurrence to a topic, while RDF does not adopt specific constructs to model occurrences.

TMRDF

It seem to be unproblematic: the occurrences can be mapped to statements whose values are either literals or URIs/blank nodes. In this case the classes and properties involved are the followings:
  • rdftm:maps-to used to map a RDF property to a TM element.
  • rdftm:Occurrence a property class that identifies the TM occurrence element (concept)

Example:

{tosca, synopsis,"http://www.azopera.com/learn/synopsis/tosca.shtml"}

becomes

tosca synopsis "http://www.azopera.com/learn/synopsis/tosca.shtml" .

synopsis rdftm:maps-to rdftm:Occurrence .

RDFTM

It seems to be more problematic: how to decide when to map a RDF property to a TM occurrence?
First approach: any property for which the guidance does not lead to interpretation as a name or an association (or an identifier?), is regarded as an occurrence. Anyway, in general a property can not be considered as an occurence.
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RDFTM.HandlingOccurrences moved from RDFTM.HandlingRelatinships on 20 Oct 2005 - 17:24 by ValentinaPresutti - put it back
You are here: RDFTM > RDFTMMappingGuidelines > DiscussionPoints > HandlingOccurrences

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