METASAN: A PERFORMABILITY EVALUATION TOOL BASED ON STOCHASTIC ACTIVITY NETWORKS.

The METASAN software package is described that assists the construction and solution of performability models based on stochastic activity networks. Stochastic activity networks, a generalization of stochastic Petri nets, permit the representation of concurrency, timeliness, fault tolerance and degradable performance in a single model. Their structure allows for direct construction of analytically tractable stochastic base models under certain well-defined conditions, as well as simulation under very general conditions. For a given system, the input to METASAN consists of two parts: a description of the structure of the net, and a description of the desired performance variables and solution method. Each part is specified in a flexible input language. This language allows the analyst to define very general performance variables in terms of the behavior of the net. The user interface and solution methods used are reviewed, and an example is given illustrating use of the package.