In this paper we describe a formalism which uses the stochastic process algebra PEPA as the inscription language for labelled stochastic Petri nets. Viewed in another way, the net is used to provide a structure for linking related PEPA systems. The combined modelling language naturally represents such applications as mobile code systems where the PEPA terms are used to model the program code which moves between network hosts (the places in the net). We describe the implementation of a tool to support this modelling formalism and apply this to model a hierarchical cellular network. 1

Abstract. Global computing applications co-ordinate distributed computations across widely-dispersed hosts. Such systems present formidable design and implementation challenges to software developers and synchronisation, scheduling and performance problems come to the fore. Complex systems such as these can benefit from the application of highlevel performance analysis methods founded on timed process algebras. In this paper we compare the use of two such approaches, the PEPA nets and EOS methods, illustrating our presentation with the example of modelling Web services. 1