Program modelling with Petri Nets: the CVS example

摘要

The behavior of a computer program can be seen as a succession of events that modify its state or the state of the system where it is executed, that is, it can be seen as a Discrete Event Dynamic System (DEDS), so it is possible to use the different methods for modelling DEDS to describe the behavior of a program. However, no all methods are equal. Today is frequent to have distributed or concurrent applications. One example is the Concurrent Version System (CVS) that allows the control of the development of programs through distributed environments. In the same category can be considered many kinds of documents that result of the collaboration of geographically spread group of persons. The contribution of the present work is to use Petri Nets as a way to describe -informally and formally- the behaviour of a program that has a concurrent behavior as is CVS. The resulting model can serve as a formal specification -that can be mathematically analyzed-, as a pedagogic aid or as a simulator -that can help simulate the effects of the program. The model helps to understand the effects and the interactions of the program with its environment.