3 Mar 2004
CS 3243 - Chapter 8
15
Equality
nterm1 = term2 is true under a given interpretation if and only if term1 and term2 refer to the same object
n
nE.g., definition of Sibling in terms of Parent:
¡"x,y Sibling(x,y) Û [Ø(x = y) Ù $m,f Ø (m = f) Ù Parent(m,x) Ù Parent(f,x) Ù Parent(m,y) Ù  Parent(f,y)]