Re: Modelling Disjoint Subtypes

From: Dimitri Furman <>
Date: Wed, 28 Mar 2007 20:08:14 -0000
Message-ID: <Xns9901A3F28BAABdfurmancloud99_at_127.0.0.1>

On Mar 28 2007, 10:39 am, "V.J. Kumar" <> wrote in news:Xns99016C61C8E14vdghher_at_194.177.96.26:

> "David Portas" <> wrote in

>> Yet another answer is addressed by Date in McGovern with their
>> "Orthogonal Design" principle. Potential ambiguity is created if the
>> same predicate is represented in multiple places in the schema
>> because of multiple relvars with meanings that "overlap".

> But we are discussing the disjoint case such that thanks to the
> constraints the meanings do not overlap.

But see Section 8 in Part 2 of the above article. It is not that just the meanings of two base relvars should not overlap - the meanings of two distinct projections of these relvars should not overlap either.

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Received on Wed Mar 28 2007 - 22:08:14 CEST

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