SPNL: Processes as Language-Oriented Building Blocks of Stochastic Petri Nets

This paper presents a modeling paradigm which combines graphical and textual elements for the structured specification of performance and dependability models based on stochastic Petri nets. The aim is to manage the complexity of model specification. In the proposed framework processes are encapsulated submodels which are building blocks as known from modular programming languages. Process interaction is possible via ports, rewards, and result measures. Ports are arcs crossing the process boundaries. Rewards and result measures represent the internal state and actions of a process and are defined in a unified structured manner. These concepts allow a generic representation of refinement and fusion of elements and of synchronous as well as asynchronous communication. The syntax is described informally by examples and formally by a grammar. The semantics is given by ordinary stochastic Petri nets and is independent of a tool environment. Two modeling examples are given to illustrate the flexibility of the approach: a multistage interconnection network and a wireless LAN MAC protocol.