The importance- or, at least, perceived importance --of enterprise modeling is attested to not only by the sheer numbers of enterprise models but also by the wide variety of modeling methods. This proliferation of modeling methods is a double-edged sword. On the one hand, methods tailored to specific kinds of information enable modelers to create clear, better focused models of the desired sort. On the other hand, because most enterprise modeling methods are ill-defined, both legacy models and current models are difficult to interpret by anyone other than the original creators. Hence, both the reuse of legacy models and the integration of current models across different aspects of an enterprise are, for all practical purposes, impossible. The purpose of this paper is to illustrate an approach to the definition of modeling method ontologies that provides a rigorous foundation for the reuse and integration of enterprise models.