State Model. A state model illustrates the lifecycle for instances of a particular object type. The state model depicts the major stages (states) that an instance of the object type can undergo, the allowable transitions between states, and the methods which transition the object from state to state.
The focus of a state model is typically an object type; however, a state may have a component model consisting of its substates. A substate is a partition of a more generic state. Transitions which occur between the superstates (more generic states) are connected at the substate level. For modeling convenience, transitions which are not attached to the substates are assumed to be valid for all substates.