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Published online by Cambridge University Press: 15 November 2003
Branching programs are a well-established computation model for boolean functions,especially read-once branching programs (BP1s) have been studied intensively. Recently two restricted nondeterministic (parity)BP1 models, called nondeterministic (parity) graph-driven BP1s and well-structured nondeterministic (parity) graph-driven BP1s, have been investigated. The consistency test for a BP-model M is the test whether a given BP is really a BP of model M. Here it is proved that the consistency test is co-NP-complete for nondeterministic (parity) graph-driven BP1s.Moreover, a lower bound technique for nondeterministic graph-driven BP1sis presented. The method generalizes a technique for the well-structured modeland is applied in order to answer in the affirmative the open question whether the model of nondeterministic graph-driven BP1s is a proper restriction of nondeterministic BP1s (with respect to polynomial size).