Object Oriented Software Architecture Design based on UML/Petri Net approach for deadlock prevention of Real Time Systems

The objective of this article is to present an approach based on UML dynamic diagrams and on Petri Net Objects for the deadlock prevention of Real Time Systems. The main idea consists of translating the sequence diagrams which express the initial specifications of the system in a unique Petri Net model which represents the global behaviour of the entire system and which belongs to the special class of Petri Nets called Simple Sequential Process with Resources. After the detection of possible unmarked siphons in the structure of the global model, a deadlock prevention strategy based on the addition of local control places is applied in order to remove structural deadlocks. The augmented Petri Net model is then translated into a set of collaboration and state-transition diagrams which represent the final deadlock free UML specification. Finally, a software architecture free of deadlocks based on an object which contains the global behaviour of the system and which centralises all the interactions between the software objects is presented. The approach is illustrated through an example of Real Time System used at the global coordination level of a Batch System.