| Formalism is a powerful tool for precisely defining and analyzing Discrete Event Simulation (DES). Many formalisms, such as FSA, GSMP, DEVS, Petri Net, SPADE, etc., have been proposed. These formalisms have proved useful for modeling individual systems. However, they become ineffective for some large-scale systems. For instance, modern simulation federations often involve many participants, which are geographically distributed. Each participant may implement federates using different technologies. In addition, existing federates may retire from the federation, while new federates may enter into the federation. This may require a change in the control flow of the simulation to reflect a frequently changing business model. Therefore, modern simulation federations have three unique characteristics: heterogeneous, distributed, and adaptive. As a result, formalisms for modern simulations should also provide companion semantics, such as: (a) compositing heterogeneous systems into larger ones; (b) coordinating distributed systems; and (c) evolving existing systems into new ones without interrupting the current executions. This thesis proposes a new formalism---called PiDES. It develops formal models for individual DES federates and runtime infrastructure based on stochastic pi-calculus and High Level Architecture. In order to demonstrate the feasibility and potential benefits of the proposed formalism, a language definition and an interpreter of PiDES, along with a prototype implementation of PiDES-RTI are also developed. The major contribution of this research is to provide a unified approach to modeling and coordinating complex adaptive simulation systems with rigorous semantics, high reconfigurability, and seamless scalability. |
