Combining sequence diagrams and OCL for liveness.

Sequence diagrams in UML 2.0 have been considerably extended, partially influenced by variants of Message Sequence Charts (MSCs) and Live Sequence Charts (LSCs). However, sequence diagrams cannot satisfactorily express liveness/progress properties or differentiate between necessary and possible behaviour. To address this limitation, we propose to use an OCL template for liveness and enrich sequence diagrams with constraints as needed. We argue that our extended sequence diagrams are more expressive than LSCs. Further, if automatic code generation from inter-object behaviour specifications is feasible it will lead to more realistic solutions. Additionally, we discuss several problems and ambiguities in sequence diagrams as defined in the UML 2.0 superstructure specification. We discuss directions for future work.© 2004 Elsevier B.V. Open access under CC BY-NC-ND license