The previous best upper bound on the complexity of deciding bisimilarity between normed context-free processes, due to Huynh and Tian, is that the problem lies in the second level of the polynomial hierarchy: their algorithm guesses a proof of equivalence and validates this proof in polynomial time using oracles freely answering questions which are in NP. In this paper we improve on this result by presenting a polynomial-time algorithm which solves this problem. As a corollary, we have a polynomial algorithm for the equivalence problem for simple context-free grammars.
['Yoram Hirshfeld', 'Mark Jerrum', 'Faron Moller']
A polynomial algorithm for deciding bisimilarity of normed context-free processes