Ordering actions in sequence diagrams of UML

The Unified Modeling Language (UML) proposes a set of models but does not have a methodology that clearly fixes both the use of these various models (diagrams) and the semantic links able to exist between them. In particular, the interaction diagrams of UML do not have, according to the current metamodel, an operational semantics defining formally how such a diagram is executed. The objective of this article is twofold: to propose a step towards a formal semantics to the interaction diagrams of UML by defining a partial order between messages and actions; and to generate a Petri net that defines the semantics of this diagram. Such a semantics can help the designer in the validation of his specifications, establishing a link between the interaction diagrams and the activity diagrams and also allowing to generate code.