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

Abstract

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.

Polymorphic scenario-based specification models: semantics and applications

“…We consider only well-formed diagrams, that is, diagrams that indeed induce a partial order (see [40]). The unwinding structure is made of a set of cut-states S (with a designated minimal cut-state s min ∈ S), and a partial (transition) function R :…”

Extending LSCs for Behavioral Signature Modeling

“…Class diagrams are used to build a hierarchy of messages and describe the structure of the system. Live Sequence Charts are an extension of Message Sequence Charts and UML 2 Sequence diagrams and preserve the graphical appeal and intuitiveness of MSCs [20]. This enables the developer to start modeling right away by extending his knowledge stepwise for the special properties of the languages.…”

Check It Out: On the Efficient Formal Verification of Live Sequence Charts

“…LSC specifications may well be played in following [12] and then strengthened for formal verification using the features from [5]. Furthermore we assume well-formed LSCs [2], i.e. LSCs without internal contradictions.…”

“…Then the evaluation time for the condition is well-defined. This criterion is easily [2] checkable on the abstract syntax of the LSC. The observer automaton construction of [15] as introduced in Sect.…”

“…Scenario-based approaches in general and Live Sequence Charts (LSCs) [1] in particular have shown adequate for the formal specification of inter-object requirements on distributed systems in formal, model-based development(cf. [2] for references). That is, requirements on a system under design are formally specified by LSCs before a model of the system is built.…”