# state - Statecharts By Kendra Cooper Contents Introduction...

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Statecharts By Kendra Cooper Contents Introduction State Diagrams Depth (hierarchy) Orthogonality (concurrency) Broadcast Communication Example Problems Introduction Statecharts were introduced by David Harel in 1987 D. Harel, “Statecharts: A visual formalism for complex systems”, Science of Computer Programming 8, 1987, pp. 231-274. Statecharts are useful for describing large, complex, reactive systems a reactive system is one which must continuously react to external and internal stimuli They are a graphic notation (“visual”) Statechart = state-diagrams + depth (also known as abstraction) + orthogonality (also known as concurrency) + broadcast communication The Statechart notation is a kind of extended FSM with abstraction, concurrency, and communication State Diagrams Composed of states, transitions transitions from one state to another happen when the event that is labeled on the arc (if any) occurs and the condition (if any) is true an output can be associated with the transition o In the diagram below, the state changes from A to B when event b occurs and the condition P is true; the output is c o c is global (can be seen everywhere in the Statechart model) c can be used as an input on a transition

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this supports communication in the model Depth (hierarchy) statecharts extend this with: o refinement, clustering o AND, OR decomposition of states (actually XOR, not OR) Example (clustering, bottom up approach)
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state - Statecharts By Kendra Cooper Contents Introduction...

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