Re: Modelling Disjoint Subtypes
Date: 24 Mar 2007 17:01:22 -0700
Message-ID: <1174780882.280836.13230_at_o5g2000hsb.googlegroups.com>
> Could anyone please provide a meaningful relational design example where
> disjoint entity subtype/supertype hierarchy would truly be beneficial ? I
> am aware of Pascal's example but do not find it convincing.
The fundamental insight is that the two (or more) entities in question
are not
identical, but they're not utterly unlike each other. I'm pretty sure
Pascal
makes that point.
Companies and individuals are not identical. But they're not utterly
unlike each
other. Both can have many mailing and shipping addresses. Both can
have
many phone numbers. Both can enter into contracts with both companies
and
individuals. Both can have tax obligations. Both can appear in
lawsuits.
So, in relational design, you might treat companies and individuals as
subtypes
of the supertype "Parties".
-- Mike SherrillReceived on Sun Mar 25 2007 - 01:01:22 CET