Thread-based analysis of sequence diagrams

Sequence Diagrams (SDs) offer an intuitive and visual way of describing expected behaviour of Object Oriented (OO) software. They focus on modelling the method calls among participants of a software system at runtime. This is an essential difference from its ancestor, basic Message Sequence Charts (bMSCs), which are mainly used to model the exchange of asynchronous messages. Since method calls are regarded as synchronous messages in the Unified Modelling Language (UML) Version 2.0, synchronous messages play a significantly more important role in SDs than in bMSCs. However, the effect of this difference has not been fully explored in previous work on the semantics of SDs. One important aim of this paper is to identify the differences between SDs and bMSCs. We observe that using traditional semantics to interpret SDs may not interpret SDs correct under certain circumstances. Consequently, we propose a new method to interpret SDs which uses thread tags to deal with identified problems.