State diagram

A state transition diagram is a graphical representation of finite automata, ie states and their transition conditions to visualize the links contained as possible transparent and unambiguous.

Applies the state transition diagram in the context of systems theory in diverse areas of computer science. An essential unification was achieved by David Harel's Statechart notation, which is widely regarded as the universal form of state transition diagrams seen. For the object-oriented software development, it has become normalized as part of the Unified Modeling Language ( UML) as a state diagram (UML). There are particular historical context, other variants of the representation.

Statecharts

Statechart is a representation of the form of finite automata in computer science, which was introduced by David Harel. The notation allows the precise specification of state-based systems. David Harel introduced several notation elements to make the complexity of large systems manageable by means of Finite State Machines:

  • Hierarchy of sub state machine, when in a state of a higher level state machine, a further complete inserted. The sub- state machines can either have their own start state, or sub-states can be jumped to directly.
  • Composition for the display of parallel state machines. Here, AND and OR - composition are possible, provide for the simultaneous or alternately switching the machine
  • Inter -level transitions, which can also result in a lower state to a state another level and vice versa.
  • History connector that stores for a sub state machine at the exit of the last occupied state to take this state back on re-entry in the sub- state machine. The history connector is listed with a circled H.
  • Condition connector that ( a transition) transferred a state transition depending on a condition in disjoint in different target states. The Condition - connector is listed with a circled C.
  • Temporal logic can be used in the transitions to specify, for example, timeouts.
  • Entry, exit, Throughout - Actions of conditions that specify which actions that are executed when entering, leaving or while within a state. Thus the number of times the Throughout action depends on the timing of the state machine.

Tools

In addition to the UML tools state transition diagrams are also a number of other both open commercial tools implemented, eg ( Incomplete list ):

  • MathWorks Stateflow for MATLAB / Simulink
  • Case/4/0
  • ETAS ASCET
  • Telelogic Statemate
  • PikeTec Test Tool Time Partition Testing ( TPT)
  • National Instruments MatrixX
  • Easy code
  • YAKINDU statechart tools (open source)
Finite-state machine ETAS Group
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