Analysis of CP-nets

The first analysis method is interactive simulation. It is very similar to debugging and prototyping. This means that we can execute a CP-net model, to make a detailed investigation of the behaviour of the modelled system. It is possible to set breakpoints and to visualise the simulation results by means of different kinds of graphics, e.g. Message Sequence Charts (also know as event traces).

The second analysis method is automatic simulation which is similar program execution. It allows a fast execution of thousands or millions of transitions. The purpose is to investigate the functional correctness of the system or to investigate the performance of the system, e.g. to identify bottlenecks, to predict the use of buffer space or the mean/maximal service time.

The third analysis method is occurrence graphs (also called state spaces or reachability graphs). The basic idea behind occurrence graphs is to construct a directed graph which has a node for each reachable system state and an arc for each possible state change. Obviously, such a graph may become very large, even for small CP-nets. However, it can be constructed and analysed totally automatically, and there exist techniques which makes it possible to work with condensed occurrence graphs without losing analytic power. These techniques build upon equivalence classes.

The fourth analysis method is place invariants. This method is very similar to the use of invariants in ordinary program verification. The user constructs a set of equations which is proved to be satisfied for all reachable system states. The equations are used to prove properties of the modelled system, e.g., absence of deadlock.