Re: insert to projection

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? 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 relation. Received on Sun Sep 06 2009 - 21:20:05 CEST