State Diagram

Icon

The icon is of a diagram with a state in it.

Owner Hierarchy/Prerequisites

• A state diagram shows the contents of precisely one state machine.

• The state diagram always shows the complete state machine.

• Each state machine needs one behaviored classifier; its states should be described by the machine.

Use

The state diagram can be created in the Model Structure below a behaviored classifier.

Dependencies between states and elements from other diagrams are shown in the whiteboard diagram.

Elements in the State Diagram

The following model elements can be shown as nodes and edges in state diagrams:

Icon	Element	Description
	State Machine	A state machine describes a system using states and transitions between these states. A state machine describes a hypothetical machine ("finite machine") which always exists within a set of finite states. State machines primarily map behaviors of classes. Unlike activities which describe activities, states which an object can have during its lifecycle are set in state machines. Conditions and controls are used to set which transitions (state transitions) can be executed.
	Region	Regions are used to model parallel flows. Each state machine contains at least one region. Each region contains multiple states; one of these states is always active.
	Init State	An init state shows the starting point for entering a state machine. This is the starting point which flows to the first state in the machine.
	Final State	The final state shows the end point of a state machine. The state machine has finished running once this point is reached.
	Terminator	Reaching a terminator cancels the state machine's execution and also ends the lifecycle of the classifier being described at the same time.
	State	A simple state maps a situation; a special condition applies for it during its progression. A state is used to model a situation; it executes a relatively long-lasting task. The system is in the respective state while the task is being processed.
	Entry point	Entry points merge similar inflowing transitions into one composite state.
	Exit point	Exit points combine similar outflowing transitions into one composite state.
	Shallow history	A shallow history stores the last active substate of a composite state once it is left.
	Deep history	A deep history stores the last active substate of all hierarchy levels of a composite state once it is left.
	Trigger	Triggers are used to trigger internal or external transitions.
	Decision	Decisions enable single or multiple transitions to be selected using a decision criteria.
	Fork/join	Forking splits a transition into multiple parallel target states. Joining ends this.
	Junction	Junctions can be used for transitions nested one after another.
	Transitions can run via one or more pseudo states to show complex relationships between states.	A transition is a directed relationship between one source and one target state. The source state is inactive for this and the target state is active. You can enter a condition for a transition if required. The transition will then only be run through if the condition is met at the time of the evaluation.

Example of a State Diagram

Further Information

http://www.uml.org/