A connection point reference represents a usage (as part of a submachine state) of an entry/exit point defined in the statemachine reference by the submachine state.

A guard is a condition or restriction expressed in natural language text or in a machine readable language that must be fulfilled for a transition to become possible.

A region is an orthogonal part of either a composite state or a state machine. It contains states and transitions.

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.

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.

A protocol transition specifies a legal transition for an operation.

Transitions of protocol state machines have the following information: a pre condition (guard), on trigger, and a post condition.

Every protocol transition is associated to zero or one operation (referred BehavioralFeature) that belongs to the context classifier of the protocol state machine.

A transition is a directed relationship between a source vertex and a target vertex.

It may be part of a compound transition, which takes the state machine from one state configuration to another, representing the complete response of the state machine to an occurrence of an event of a particular type.