Within a given modeling platform, modeling tools interoperate efficiently. They are generally written in the same general purpose language, and use a single modeling frame- wok (i.e., an API to access models). However, interoperability between tools from different modeling platforms is much more problematic. In this paper, we argue that fUML may be leveraged to ad- dress this issue by providing a common execution language, and by abstracting modeling frameworks into generic actions that perform elementary operations on models. Not only can user models benefit from a unified execution semantics, but modeling tools can too.