State diagram

A state diagram is a type of diagram used in computer science and related fields to describe the behavior of systems. State diagrams require that the system described is composed of a finite number of states; sometimes, this is indeed the case, while at other times this is a reasonable abstraction. Many forms of state diagrams exist, which differ slightly and have different semantics.

Overview

State diagrams are used to give an abstract description of the behavior of a system. This behavior is analyzed and represented as a series of events that can occur in one or more possible states. Hereby "each diagram usually represents objects of a single class and track the different states of its objects through the system".

State diagrams can be used to graphically represent finite state machines. This was introduced by C.E. Shannon and W. Weaver in their 1949 book "The Mathematical Theory of Communication". Another source is Taylor Booth in his 1967 book "Sequential Machines and Automata Theory". Another possible representation is the State transition table.

State diagram (UML)

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: