Petri Net Based System Analysis without State Explosion

cally by help of general Petri net analysis tools. Therefore, they are reproducible in an objective way. For a general framework for Petri net based development and analysis of dependable systems, we conclude the following design criteria. At first, dedicated technical languages are needed to express functional, safety, and performance requirements as well. Second, the framework has to be customizable. Its components (editors, analysis tools, simulation tools, code generation facilities) should be interchangeable. For a given configuration, user guidelines are required showing which analysis techniques are recommendable in which order for a given analysis question. Additionally, design criteria are required which promotes meaningful analyses at each phase of development. For specific application areas, dedicated configurations of the framework can be defined involving also an adaptation of the libraries and the terminology of the user interface. For instance, in manufacturing control in general, it seems to be possible to compile Petri net libraries of • patterns which describe the communication structure of certain devices on a cooperation level (for our production cell case study , three such patterns are identifiable, each of them applicable to at least two devices), • patterns which are suitable to describe elementary motion steps of the devices, and • the associated environment models. Using these libraries, it will be possible to develop control programs for the supported types of manufacturing systems by composition and refinement of instantiated net patterns. In particular, in case of programmable logic controllers, the tool box's user interface may be adapted to the notions of the IEC 1131-3 standard. That's why these transitions are superfluous in the given case, and we are able to optimize our model by deleting them. For more details see (Heiner 1997c). We get an optimized model with the same state space as the unoptimized one, but without far less dynamic conflicts. For this version, the liveness for each transition of the considered pusher chains has been proven by model checking the corresponding temporal formula based on the branching process' prefix. Special analysis deals with properties reflecting the intended special functionality. The verification of safety properties is here especially important. Therefore we will stress this topic in the following paragraph. (a) safety There are different analysis techniques available to prove the unreachability of unsafe states: Facts (INA): The unsafe states may be modelled as facts (special transitions which are expected to become never enabled). But, the evaluation of …