On legacy system reusability based on CPN and CCS formalism

Most legacy systems have been developed in such a monolithic way that they can be used only for solving certain specific problems in the domain where the systems reside. When introducing improved or new business processes into the systems, and/or employing new information technologies such as object technologies or component-based software development methods, this monolithic property often becomes an obstacle. Usually, one cannot enhance the legacy systems because of this property. In this paper, we propose a formal approach which could be soundly applied for modeling such business processes and legacy systems as well. By means of this approach, we can easily evaluate equivalences and differences between them, and find the reusable parts of the legacy systems. Colored Petri nets (CPN) and the Calculus of Communicating Systems (CCS) are used for constructing this formal approach. A simple example from a mail-order processing system is illustrated to show how this approach works