Cellular functions are realised by complex networks of chemical reac-tions. In most cases, however, several reaction schemes can be con-sidered as plausible a-priori hypotheses. This project aims at providing a set of methods that can be used to safely discard hypotheses on the basis of qualitative properties or measurement information. Methods include the construction of safe"" approximating automata and, more recently, the application of Feinberg"s Chemical Reaction Network Theory. The latter connects qualitative properties of ODEs describing a given reaction network (as, e.g., the existence of multiple steady states) to the network structure. In particular, its assertions are inde-pendent of parameter values and only assume that all kinetics are of mass-action form. First results are reported in .