  We consider graph complexes with a flow and compute their cohomology. More
specifically, we prove that for a PROP generated by a Koszul dioperad, the
corresponding graph complex gives a minimal model of the PROP. We also give
another proof of the existence of a minimal model of the bialgebra PROP from
math.AT/0209007. These results are based on the useful notion of a 1/2 PROP
introduced by Kontsevich in an e-mail message to the first author.
