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To: info-hol@leopard.cs.byu.edu
Subject: Terminological questions
Date: Mon, 27 Jun 94 23:00:56 PDT
From: chou@cs.ucla.edu


Let S1 and S2 be two sets and R a relation between S1 and S2
(ie, R is a subset of S1 X S2) which will be written as an infix.
We can define two relations, A(R) and B(R), between subsets of S1
and subsets of S2:

    A(R)(P1)(P2) = !x1. x1 in P1 ==> ?x2. x2 in P2 /\ x1 R X2
    B(R)(P1)(P2) = !x1 x2. x1 R X2 ==> x1 in P1 ==> x2 in P2

Are there standard names for operators A and B in mathematics?

- Ching Tsun