Re: insert to projection

From: Mr. Scott <>
Date: Fri, 4 Sep 2009 22:44:35 -0400
Message-ID: <>

"paul c" <> wrote in message news:DGbom.42669$Db2.5159_at_edtnps83...
> Why do implementation languages not allow this? Surely not for logical
> reasons? We can delete from projection because NOT Pa implies NOT Pab,
> eg., <NOT> R{a} -> <NOT> R{a,b}. Logically, we can insert to projections
> because Pab implies Pa. Isn't the problem really a language deficiency?

I don't understand. Is the binary predicate P somehow related to the unary predicate P, and if so, how exactly? Received on Fri Sep 04 2009 - 21:44:35 CDT

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