Rules

• Name: The value can be anything.

  The name of the diagram.

• Documentation: The value can be anything.

  A textual description of the element.

An element of one of the following kinds:

• Final State (Final State)

  A special kind of state signifying that the enclosing region is completed.

  If the enclosing region is directly contained in a state machine and all other regions in the state machine also are completed, then it means that the entire state machine is completed.

• Protocol State Machine (Protocol State Machine)

  A protocol state machine is always defined in the context of a classifier. It specifies which operations of the classifier can be called in which state and under which condition, thus specifying the allowed call sequences on the classifier's operations.

  A protocol state machine presents the possible and permitted transitions on the instances of its context classifier, together with the operations which carry the transitions. In this manner, an instance lifecycle can be created for a classifier, by specifying the order in which the operations can be activated and the states through which an instance progresses during its existence.

• State (State)

  A state models a situation during which some (usually implicit) invariant condition holds.

  The states of protocol state machines are exposed to the users of their context classifiers. A protocol state represents an exposed stable situation of its context classifier: when an instance of the classifier is not processing any operation, users of this instance can always know its state configuration.

• State Machine (State Machine)

  State machines can be used to express the behavior of part of a system.

  Behavior is modeled as a traversal of a graph of state nodes interconnected by one or more joined transition arcs that are triggered by the dispatching of series of (event) occurrences. During this traversal, the state machine executes a series of activities associated with various elements of the state machine.