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Re: Relation Schemata vs. Relation Variables

From: Keith H Duggar <duggar_at_alum.mit.edu>
Date: 20 Aug 2006 17:58:14 -0700
Message-ID: <1156121894.123519.209510@74g2000cwt.googlegroups.com> 





Brian Selzer wrote:


> For instance, consider the following states for a relation

> describing people's marital status, and a transition

> constraint that says: Single people can't become Divorced:

>

> Current                      Proposed

> Jane Jones Married    Jane Jones Married

> Jane Smith Single       Jane Smith Divorced




Please express this constraint using relational calculus.
I'm particularly interested to see how "people" and "become"
are expressed.



Thank you.




Received on Sun Aug 20 2006 - 19:58:14 CDT












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