Robert Mayer-Strasse 11-15, D-6054 Frankfurt a. M., Germany
SVM HeaderParse 0.2
Abstract. The ambiguity of a nondeterministic finite automaton (NFA) N for input size n is the maximal number of accepting computations of N for an input of size n. For all k, r ∈ N we construct languages Lr,k which can be recognized by NFA’s with size k·poly(r) and ambiguity O(n k), but Lr,k has only NFA’s with exponential size, if ambiguity o(n k) is required. In particular, a hierarchy for polynomial ambiguity is obtained, solving a long standing open problem (Ravikumar and Ibarra, 1989, Leung, 1998). 1.