Re: choice of character for relational division
From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 01 Apr 2007 20:49:54 GMT
Message-ID: <SVUPh.14623$6m4.923_at_pd7urf1no>
Date: Sun, 01 Apr 2007 20:49:54 GMT
Message-ID: <SVUPh.14623$6m4.923_at_pd7urf1no>
Marshall wrote:
...
> It certainly looks as if & is overloaded but ... maybe it isn't!
>
> Suppose the relational = operator is closed over relations.
> That is, its result, rather than being some specific boolean
> type, was instead necessarily a relation. Any empty relation
> would be interpreted as false and any nonempty relation
> is true. In this case we don't need any attributes on the
> result, just to know whether it's empty or not. So
>
> true = DEE
> false = DUM
>
> and the various & characters in the above are *all* natural join.
> ...
Why close it over just relations? Eg., why not always produce DEE or DUM?
p Received on Sun Apr 01 2007 - 22:49:54 CEST