Re: teaching relational basics to people, questions

From: Bob Badour <>
Date: Sat, 28 Nov 2009 17:56:36 -0400
Message-ID: <4b119c99$0$5326$>

paul c wrote:

> Mr. Scott wrote:

>> But what if there is more than one row?  The information content of a 
>> table is the logical sum (disjunction) of the information represented 
>> by each row.

> The conventional view is that is that the information in a table is the
> logical conjunction of the information represented by the rows in the
> table. Just because the table is formed by a summing operation doesn't
> change that.

Ahem. Conjunction of the domains. A relation is the extension of a predicate. That predicate can be represented as the disjunction of the tuples.

>> But those can easily be transformed into into truth-valued 
>> constraints, can't they?

> Not easy if users aren't required to know default values. I don't see
> why they should. Contrary to Dr. Strangelove, the whole point of
> defaults is to avoid users having to know them!

Defaults are not constraints.

is there something in it for them, like maybe bailouts, if they can 
panic us into doing something politically to cover them?

November 19, 2007 - John S Bolton
Received on Sat Nov 28 2009 - 15:56:36 CST

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