A solution of an interleaving decision problem by a partial order technique
We show that the following problem is decidable: given expressions E1 and E2 constructed from variables by the regular operations and shuffle, is the identity E1 = E2 true for all instantiations of its variables by strings? Our proof uses the notations developed in the causal approach to concurrency. As a byproduct we obtain decidability of similar equivalence for other formalisms. In particular, we prove decidability of split equivalence for Petri nets. Our paper also provides an alternative proof for a characterization of split equivalence recently given by W.Vogler.