Finite State Machine

Finite State Machines are all around us. From microwave ovens to dishwashers, from elevators to computers, from cars to airplanes, everything inside is controlled by Finite State Machines. The use cases for Finite State Machines are countless. If you are not familiar with the concept of state machines, you can find many good explanations of what a state machine on Internet.

This chapter explains how a Finite State Machine can represent a business process. We will use the UML Sate Diagram from the previous chapter as an example:

Finite State Machine

Let's look at the definition of a Finite State Machine by comparing it with the knowledge we have gained about a business process, its sub-processes, and how to model them.

· FSM is an abstract machine that can be in exactly one of a finite number of states at any given time. – This statement also applies to a business sub-process, since at any given time it can be in exactly one state.

· The FSM can change from one state to another in response to some external inputs. – This statement also applies to a business sub-process, since only external event (indicated by trigger in the diagram above) causes a transition of the sub-process from its current state to one of the target states.

The following statements can be directly applied to a sub-process, and we have already used them in the same way in previous chapters:

· The change from one state to another is called a transition.

· An FSM is defined by a list of its states, its initial state, and the conditions for each transition.

· An input that doesn't cause a change of state (like “Searching patient’s data” in our example) is represented by a circular arrow returning to the original state .

And the last statement “ State machine can also be represented by a directed graph called a state diagram” summarizes all the above, allowing us to say that a programmed state machine can represent any business process.

Alternative Definition of a Business Process

Business Process is a programmed Finite State Machine.

Table of Content Introduction into Business Process Previous: UML State Diagrams Next: States and Transitions