The Good, the Bad and the Ugly: Well-Formedness of Live Sequence Charts
The Life Sequence Chart (LSC) language is a conservative extension of the well-known visual formalism of Message Sequence Charts. An LSC specification formally captures requirements on the inter-object behaviour in a system as a set of scenarios. As with many languages, there are LSCs which are syntactically correct but insatisfiable due to internal contradictions. The authors of the original publication on LSCs avoid this problem by restricting their discussion to well-formed LSCs, i.e. LSCs that induce a partial order on their elements.
This abstract definition is of limited help to authors of LSCs as they need guidelines how to write well-formed LSCs and fast procedures that check for the absence of internal contradictions. To this end we provide an exact characterisation of well-formedness of LSCs in terms of concrete syntax as well as in terms of the semantics-giving automata. We give a fast graph-based algorithm to decide well-formedness. Consequently we can confirm that the results on the complexity of a number of LSC problems recently obtained for the subclass of well-formed LSCs actually hold for the set of all LSCs.
KeywordsPrecedence Relation Instantaneous Message Local Invariant Concrete Syntax Precedence Graph
- 2.Bohn, J., Damm, W., Wittke, H., Klose, J., Moik, A.: Modelling and validating train system applications using Statemate and Live Sequence Charts. In: Proc. IDPT 2002, Society for Design and Process Science (June 2002)Google Scholar
- 3.Bontemps, Y.: Relating Inter-Agent and Intra-Agent Specifications. PhD thesis, University of Namur (Belgium) (April 2005)Google Scholar
- 4.Bontemps, Y., Heymans, P., Kugler, H.: Applying LSCs to the specification of an air traffic control system. In: Proc. SCESM 2003 (2003)Google Scholar
- 10.ITU-T. ITU-T Rec. Z.120: Message Sequence Chart (MSC). ITU-T, Geneva (1999)Google Scholar
- 11.Klose, J.: Live Sequence Charts: A Graphical Formalism for the Specification of Communication Behavior. PhD thesis, C. v. O. Universität Oldenburg (2003)Google Scholar
- 12.Knieke, C., Huhn, M., Goltz, U.: Modelling and simulation of an automotive system using lscs. In: Houmb, S.H., Jürjens, J., France, R. (eds.) Proc. CSDUML 2005, TUM (September 2005)Google Scholar
- 14.Schinz, I., Toben, T., Mrugalla, C., Westphal, B.: The Rhapsody UML Verification Environment. In: Cuellar, J.R., Liu, Z. (eds.) Proc. SEFM 2004, pp. 174–183 (September 2004)Google Scholar
- 15.Toben, T., Westphal, B.: On the expressive power of Live Sequence Charts. In: Proceedings of the SofSem 2006 Poster Session, Matfyz Press (to appear, 2006)Google Scholar