Integrated frameworks for multi-level and multi-formalism modeling

There have been significant advances in methods for specifying and solving models that aim to predict the performance and dependability of computer systems and networks. At the same time, however, there have been dramatic increases in the complexity of the systems whose performance and dependability must be evaluated, and considerable increases in the expectations of analysts that use perform-ance/dependability evaluation tools. This paper briefly reviews the progress that has been made in the development of performance/dependability evaluation tools, and argues that the next important step is the creation of modeling frameworks and software environments that support multi-level, multi-formalism modeling and multiple solution methods within a single integrated framework. In addition, this paper presents an overview of the Möbius project, which aims to provide a modeling framework and software environment that support multiple modeling formalisms, methods for model composition and connection, and a way to integrate multiple analytical/numerical-and simulation-based model solution methods. Finally, it suggests research that must take place to make this aim a reality, and thus facilitate the performance and dependability evaluation of complex computer systems and networks.