Re: What databases have taught me
From: J M Davitt <jdavitt_at_aeneas.net>
Date: Sat, 24 Jun 2006 02:36:27 GMT
Message-ID: <Ly1ng.66111$mh.20139_at_tornado.ohiordc.rr.com>
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> Transitive closure of?
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Date: Sat, 24 Jun 2006 02:36:27 GMT
Message-ID: <Ly1ng.66111$mh.20139_at_tornado.ohiordc.rr.com>
Dmitry A. Kazakov wrote:
> On Fri, 23 Jun 2006 16:31:02 +0200, Bruno Desthuilliers wrote:
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>>>What kind >>>of operation do you think is unsupported by the algebra ? >> >>I don't know how this translates in english, the french term is >>"fermeture transitive d'un graphe". IOW, if I have (minimal example):
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> Transitive closure of?
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Directed, acyclic graphs.
Date and Darwen say TCLOSE - their operator denoting the transitive closure operation - on a binary relation having attributes of the same type yields a superset of that relation if there exists a sequence of values representing a path. [My paraphrase.] Given an appropriate relation R, TCLOSE R would contain {x, y} if either {x, y} exists or there exist some {x, a}, {a, b}, {b, ...}, {..., y}.
There is, as far as I know, nothing for networks. Received on Sat Jun 24 2006 - 04:36:27 CEST