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RDFTM.HandlingNaryRelationshipsr1.5 - 10 Oct 2005 - 20:32 - ValentinaPresuttitopic end

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N-ary relationships

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

The rules are as follows:

Comments and reviews


Adhere to [Noy 05]?

In the new editor's note about N-ary relations in RDF the patterns changed. The precedent 2 patterns collapsed in one, and there is a new pattern which uses rdf:List



  • Pattern 1:
    • this pattern allows to represent a relation with different aspects or attributes, a relation with a subject distinguished by the other participants, a relation with no distinguished subject;
    • the n-ary relation is represented by a new class and n new properties.

P rdf:type X.    P rA A .   P rB B .   P rC C .   
P rdf:type X.    A rA P .   P rB B .   P rC C .   

  • Pattern 2:
    • This pattern allows to represent those relations where all but one of the participiant do not have a specific role;
    • The n-ary relation is represented by the subject pointing to the list, where each list item points to its content and to the rest of the list.


The question is: what does an n-ary association in Topic Maps become when we convert it to RDF? And is there going to be a way to convert an RDF resource into an n-ary association when converting to Topic Maps? Those are the questions, I think. Noy's note is probably only helpful in that it has a proposal for the former, but IMHO what she calls n-ary relationship is not the same as an n-ary association in Topic Maps, so it may be best to simply ignore the note.

Lars and I agree that Noy's third example of the pattern 1 is not a good example. It seems to be a poor example by modeling point of view. The best thing to do is to involve Natasha Noy in this discussion highlighting this point. Furthermore, Christopher Welty is working on a vocabulary for representing N-ary relations. We agree that using that vocabulary is mandatory. I asked about a first draft of the vocabulary, Christopher said he was going to work on it last weekend. I will ask again for news and would like to propose to work out it together.

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