Re: insert to projection
Date: Sun, 06 Sep 2009 19:35:19 GMT
Vadim Tropashko wrote:
> On Sep 6, 11:40 am, paul c <toledobythe..._at_oohay.ac> wrote:
>> If I read that worksheet right, it means we can't delete <p 1, q 'a'> >> from a conventional table or relvar and expect <p 1> to be negated, >> which I don't argue with. (whereas I don't think anybody disagrees that >> we already can delete <p 1> and expect <p 1, q 'a'> to be negated.)
> What do you mean by negating a tuple? ...
Retracting/negating the proposition the tuple stands for.
View update expresses increments/
> decrements of the base relations in terms of increments/decrements of
> the view(s). Compare it to (a relatively simple) view maintenance
> problem where increments/decrements of the view(s) in terms of
> increments/decrements of the base relations. Maintenance of the
> projection view (or any other relational expression for that matter)
> is easy: just take a projection of any incremant/decremant of the base
No argument that it's conceptually easy, but in practice the base could have a dozen such projections. Received on Sun Sep 06 2009 - 21:35:19 CEST