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From: Jan Hidders <jan.hidders@REMOVETHIS.pandora.be>
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Newsgroups: sci.logic,comp.databases.theory
Subject: Re: deductive databases
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Date: Fri, 20 May 2005 18:49:32 GMT
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Xref: dp-news.maxwell.syr.edu sci.logic:94249 comp.databases.theory:30936

Torkel Franzen wrote:
> Jan Hidders <jan.hidders@REMOVETHIS.pandora.be> writes:
> 
>>"There exists a formula over two binary predicates R and S that is true 
>>iff S is the transitive closure of R."
> 
>   True in what structure?

In a structure with the two binary relations R and S. The formula should 
be true for precisely those structures in which S is the transitive 
closure of R.

-- Jan Hidders