Interface-Oriented Classification of DEVS Models1

fC :M C → and M m f m c c c C = ∈ = ∈ M , C a f n s . Model classification is a way to structure and handle knowledge about systems. Using the models external message interface as the classification criterion lays emphasis on the fact that atomic and coupled DEVS models are modular and interchangable model components. Interface-Oriented Classification is a means to formalize the conditions of component replacement and coupling valitity. It can be used as the basis of advanced modeling methods like multi-modeling and modeling of structurally variant systems. There are various classification criteria to be used with simulation models. Most often, an implementation oriented classification is done. In this case, models belong to the same class if their implementation is equivalent. Classification criteria are e.g. whether a DEVS model is an atomic or coupled model or what state variables are used. For most of the application areas for classification the implementation has no significance. Instead, we need to know about which incoming external events a model can process, which outgoing external events a model produces and how it can be coupled to other models. These properties are what we call the models interface. In the following sections, we propose a classification scheme where the models interface is used as a classification criterion. We call this scheme the Interface-Oriented Classification of DEVS models.