It is a tacit assumption of m u c h linguistic inquiry that all distinct derivations of a string should assign distinct meanings. But despite the tidiness of such derivational uniqueness, there seems to be no a priori reason to assume that a g r a m m a r must have this property. If a grammar exhibits derivational equivalence, whereby distinct derivations of a string assign the same meanings, naive exhaustive search for all derivations will be redundant, and quite possibly intractable. In this paper we show how notions of derivation-reduction and normal form can be used to.
