Pseudostates

The Initial element represents a pseudostate used to denote the default state of a Composite State; there can be one Initial vertex in each Region of the Composite State.

Entry Point pseudostates are used to define the beginning of a StateMachine. An Entry Point exists for each region, directing the initial concurrent state configuration.

Exit Points are used in StateMachine elements and StateMachine diagrams to denote the point where the machine is exited and the transition sourcing this exit point.

The Choice pseudostate is used to compose complex transitional paths, where the outgoing transition path is decided by dynamic, run-time conditions.

Junction pseudostates are used to design complex transitional paths in StateMachine diagrams. A Junction can be used to combine or merge multiple paths into a shared transition path.

There are two types of History pseudostate defined in UML: shallow and deep history.

The Terminate pseudostate indicates that upon entry of its pseudostate, the StateMachine's execution ends.

The Activity Final element indicates the completion of an Activity; upon reaching the Final, all execution in the Activity diagram is aborted.

A Fork/Join element can be used to: 1) split a single flow into a number of concurrent flows, 2) join a number of concurrent flows or 3) both join and fork a number of incoming flows to a number of outgoing flows.