Marshall wrote:
> paul c wrote:
>
>>Marshall wrote:
>>
>>>[...]
>>
>>Thanks, and
>>
>>Okay, maybe you are right but what if project is not binary but unary?
>>Isn't the idea of treating it as a binary operator arbitrary? Is it
>>enough to say that a projection joined with the relation it was produced
>>from results in that same relation? Just wondering ...
>
> I don't see anything wrong with unary operators. But we can't really
> do PROJECT as a unary operator, because we don't have enough
> info to know what operators should be left when we're done. (If
> we were dealing with binary relations, we could define FIRST
> and SECOND, but that's of little use to us here.)
Unless project is not a single operation but a generic powerset of unary
operations. Not that I think the idea is necessarily all that useful.
Received on Fri Aug 18 2006 - 08:29:53 CDT
