Re: Modelling Disjoint Subtypes
Date: Wed, 28 Mar 2007 20:08:14 -0000
On Mar 28 2007, 10:39 am, "V.J. Kumar" <vjkmail_at_gmail.com> wrote in news:Xns99016C61C8E14vdghher_at_188.8.131.52:
> "David Portas" <REMOVE_BEFORE_REPLYING_dportas_at_acm.org> 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". >> http://www.dbdebunk.com/page/page/622331.htm
> 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.
-- remove a 9 to reply by emailReceived on Wed Mar 28 2007 - 22:08:14 CEST