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Subject: Re: [topicmaps-comment] mapping topic maps on a relation database
[Steve Pepper] > At 09:32 17/04/02 -0400, Thomas B. Passin wrote: > >[franck legoux] > > > > > > Does someone has a model to map "topic maps" on a > > > relational database ? > > > >... > > > >2) How to handle multiple role-playing topics with the same role > > Unless your application needs to be able to preserve the exact syntactic > form of the input topic map (in which case, I wish you luck :-), you can > simply exploit the rule in Annex F of XTM 1.0 relating to "Equivalence of > Multiple <member>s of the Same Role" (F.3.3) which states that: > > "An association containing multiple members, M1 and M2 of the same role R > may be equivalently defined by an association containing a single member M3 > of role R whose set of players is the union of the sets of players of role > R in members M1 and M2." > > If your input document contains a <member> element containing multiple > role-playing topics, you simply treat it as multiple <member> elements > (with the same <roleSpec>), each containing a single role-playing topic. > Right, but it requires yet one more many-to-many relationship table and yet that much more complexity in queries. Probably there is no help for it, though. I have never really analyzed potential relational models very carefully, so I don't know if there are some simplifications that can be made here. Cheers, Tom P
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