Abstract not found

Ptolemy is an open-source and extensible modeling and simulation framework. It offers heterogeneous modeling capabilities by allowing different models of computation, both untimed and timed, to be composed hierarchically in an arbitrary fashion. This paper proposes a formal semantics for Ptolemy which is modular, in the sense that atomic actors and their compositions are treated in a unified way. In particular, all actors conform to an executable interface that contains four functions: fire (produce outputs given current state and inputs), postfire (update state instantaneously), deadline (how much time the actor is willing to let elapse) and time-update (update state with passage of time). Composite actors are obtained from composition operators that in Ptolemy are called directors. Different directors realize different models of computation. This

All rights reserved.

All rights reserved.

Abstract. Complex systems demand diversity in the modeling mechanisms. One way to deal with a diversity of requirements is to create flexible modeling frameworks that can be adapted to cover the field of interest. The downside of this approach is a weakening of the semantics of the modeling frameworks that compromises interoperability, understandability, and analyzability of the models. An alternative approach is to embrace heterogeneity and to provide mechanisms for a diversity of models to interact. This paper reviews an approach that achieves such interaction between diverse models using an abstract semantics, which is a deliberately incomplete semantics that cannot by itself define a useful modeling framework. It instead focuses on the interactions between diverse models, reducing the nature of those interactions to a minimum semantics is the actor semantics, which can handle many heterogeneous models that are built today, and some that are not common today. The actor abstract semantics and many concrete semantics have been implemented in Ptolemy II, an open-source software framework distributed under a BSD-style license. 1