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Re: Modelling Disjoint Subtypes

From: Mike <mike_at_sherrillshelton.net>
Date: 24 Mar 2007 17:01:22 -0700
Message-ID: <1174780882.280836.13230@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 Sherrill
Received on Sat Mar 24 2007 - 19:01:22 CDT

Original text of this message

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