Modal Scenarios as Automata

Scenario-based modeling in live sequence charts (LSC) involves specifying multi-modal inter-object scenarios, in which events can be mandatory (hot) or possible (cold). In translating LSCs into automata over infinite words, an intermediate step constructs a kind of transition system that we call a modal state structure (MSS). Here we present MSSs as abstract forms of modal scenarios (with both mandatory, possible and forbidden behavior), which may encode more general patterns than those inherent in LSC, such as loops, alternatives and breaks. MSSs are essentially automata, in which the notion of temperature is adopted from LSCs, replacing traditional acceptance conditions.