RE: an algorith to query triple stores in SQL

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Date: Wed, 4 Sep 2002 09:37:51 -0400 (EDT)
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From: RLOZANO@clinic.ub.es
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To: www-rdf-interest@w3.org

Suppose you are asking an ontology that holds information on multinational
companies with a hierarchical relation between them:

(A class company)
(B class company)
(C class company)
(B purchasedBy A)
(C purchasedBy B)

in this model someone  that works for C works for A too. How do you manage
this?. In general, how do you manage the problem of inheritance, which is
recursive with the proposed schema ?

But you don’t need recursive questions to have problems since you use a join
of the table with itself for each clause. So, a question with a few clauses
on a model with some thousands statements will be very inefficient.

The problem is in the data model chosen, I think is too simple.

Cheers,

Raimundo Lozano

 > -----Mensaje original-----
 > De: matt@picdiary.com [mailto:matt@picdiary.com]
 > Enviado el: miércoles, 21 de agosto de 2002 21:45
 > Para: www-rdf-interest@w3.org
 > Asunto: an algorith to query triple stores in SQL
 >
 >
 >
 > Some time ago (perhaps 18 months now), inspired by the proposed SQL
 > structures for triple storage presented in
 > http://www-db.stanford.edu/~melnik/rdf/db.html , I came up
 > with a system
 > to automatically convert triples queries (in the style of RDFDB) into
 > SQL that could query a database with a schema similar to Eric Miller's
 > 'naive approach'.
 >
 > For example,
 >
 > select ( ?x ?y ) from triple where (?x worksFor ?y) (?y name 'BBC')
 >
 > is translated to
 >
 >  SELECT a1.subject as x, a1.object as y
 >  FROM triple a1,triple a2
 >  WHERE
 >  a1.pred = 'worksFor'
 >  AND a2.subject = 'BBC'
 >  AND a2.pred = 'name'
 >  AND a1.object = a2.subject
 >
 > Encouraged by (amongst others) Dan Brickley, Edd Dumbill and Libby
 > Miller, I finally got round to writing up this system and releasing
 > sample implementations in perl and php. Since I coded the original
 > system, Libby has based parts of the SquishQL query system on
 > it, and Dan
 > has in turn based some of his code on that.
 >
 > The writeup makes it explicit that I encourage reuse of the system and
 > am happy to see it put to use in projects like this. The algorithm's
 > pretty simple and is language-independent (Libby
 > transliterated it into
 > Java with many improvements, and Dan converted that code into Ruby).
 >
 > More details here: http://www.picdiary.com/triplequerying/
 >
 > Cheers,
 > Matt.
 >

Received on Wednesday, 4 September 2002 09:51:42 UTC