Converses

Two predicates are converses if they describe the same relation from opposing perspectives.


 * For any pair of predicates P, Q P and Q are converses iff
 * for all x, y,
 * P(x,y) &harr; Q(y,x)

Examples

 * 'above' vs. 'below'
 * 'in front of' vs. 'behind'
 * 'before' vs. 'after'
 * 'parent of' vs. 'child of'
 * 'huest' vs. 'host'