Re: how to prove
Date: Mon, 13 Feb 2012 22:08:17 -0800 (PST)
Message-ID: <9f744b62-ddd4-40e5-a5ac-e7a8429333eb_at_ir9g2000pbc.googlegroups.com>
On Feb 10, 5:18 pm, Helen2007 <helen.ack..._at_googlemail.com> wrote:
> How can I prove Qa: p(X,Y) is not contained in Qb: p(A,'a')? I have
> proved the containment in the other direction using mapping, but not
> sure how to proceed with this case.
I don't know this notation or terms. One can guess that you want to
prove
~(forall a [p(a, 'a')] -> forall x, y [p(x, y)])
Suggest you try a counterexample.
Googling +"Qa: p(X,Y)" +"contained in" gives a single hit 'Logical query optimization by proof-tree transformation' (Ramakrishnan/Sagiv/ Ullman/Vardi 1993) "... have frontiers that are related to the p(X, Y) nodes by Qa: p(X, Y) : a(X, Z) p(Z, ... A set of proof trees S is said to be contained in another, say, T, if every fact ...", consistent with my guess. Context is helpful for any question, like the topic or paper or textbook you're reading & it's polite when it's homework to say so.
philip Received on Tue Feb 14 2012 - 07:08:17 CET