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RDFTM.HandlingOccurrencesr1.7 - 26 Oct 2005 - 16:47 - ValentinaPresuttitopic end

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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.

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

  • rdftm:OccurrenceProperty which is defined as rdfs:subpropertyOf rdf:Property.


  • Occurences become RDF properties, which are defined to be instances of rdftm:OccurrenceProperty.


  • RDF properties which are instances of rdftm:OccurrenceProperty are translated to Topic Maps occurrences.
    • If the value of the property is a literal, then it is translated to a Topic Maps internal occurrence.
    • If the value of the property has a datatype, which is not a URI, then the property is transalted to a Topic Maps internal occurrence.
    • If the value of the property has a datatype, which is a URI, then the property is transalted to a Topic Maps external occurrence.



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


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)


{tosca, synopsis,""}


tosca synopsis "" .

synopsis rdftm:maps-to rdftm:Occurrence .


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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