The state diagram in the Unified Modeling Language is essentially a Harel statechart with standardized notation , which can describe many systems, from computer programs to business processes. In UML 2 the name has been changed to State Machine Diagram. The following are the basic notational elements that can be used to make up a diagram:
Filled circle, representing to the initial state
Hollow circle containing a smaller filled circle, indicating the final state (if any)
Rounded rectangle, denoting a state. Top of the rectangle contains a name of the state. Can contain a horizontal line in the middle, below which the activities that are done in that state are indicated
Arrow, denoting transition. The name of the event (if any) causing this transition labels the arrow body. A guard expression may be added before a "/" and enclosed in square-brackets ( eventName[guardExpression] ), denoting that this expression must be true for the transition to take place. If an action is performed during this transition, it is added to the label following a "/" ( eventName[guardExpression]/action ).
Thick horizontal line with either x>1 lines entering and 1 line leaving or 1 line entering and x>1 lines leaving. These denote join/fork, respectively.