SHARPE at the age of twenty two

<jats:p>This paper discusses the modeling tool called SHARPE (Symbolic Hierarchical Automated Reliability and Performance Evaluator), a general hierarchical modeling tool that analyzes stochastic models of reliability, availability, performance, and performability. It allows the user to choose the number of levels of models, the type of model at each level, and which results from each model level are to act as which parameters in which higher-level models. SHARPE includes algorithms for analysis of fault trees, reliability block diagrams, acyclic series-parallel graphs, acyclic and cyclic Markov and semi-Markov models, generalized stochastic Petri nets, and closed single- and multi-chain product-form queueing networks. For many of these, the user can choose among alternative algorithms, and can decide whether to get a result in the form of a distribution function (symbolic in the time variable) or as a mean or probability. SHARPE has been useful to students, practicing engineers, and researchers. In this paper we discuss the history of SHARPE, give some examples of its use, and talk about some lessons learned.</jats:p>