GUEST EDITORIAL: INTRODUCTION TO THE SPECIAL SECTION.

The seven articles selected in the journal "IEEE Transactions on Software Engineering," are from the Seventh International Workshop on Petri Nets and Performance Models (PNPM) held in Saint Malo, France, June 3-6, 1997. Giovanni Chiola of the University of Genova was program chairman. The Saint Malo meeting was the seventh workshop of the PNPM series, and followed workshops held in Torino, Italy in 1985. The first pair of papers in this special section investigate the use of the structure of a model to reduce the complexity of its solution. The first paper, entitled "Structured Solution of Asynchronously Communicating Stochastic Modules," exploits the compositional view of a model provided by this formalism to generate an underlying state space and find the steady-state marking occupancy probabilities of the resulting reachability space in an efficient way. In the second paper, the author proposes a new compositional method for generating and storing the underlying state space of a model in a structured fashion. The next two papers in the special section describes new methods for efficiently obtaining the transient solution of stochastic Petri net models.