The Good, the Bad and the Ugly: Well-Formedness of Live Sequence Charts

  • Bernd Westphal
  • Tobe Toben
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3922)


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.


Precedence Relation Instantaneous Message Local Invariant Concrete Syntax Precedence Graph 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Bernd Westphal
    • 1
  • Tobe Toben
    • 1
  1. 1.Carl von Ossietzky Universität OldenburgOldenburgGermany

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