Finite State Machine

In the previous chapter, we used a state diagram to describe a sub-process. Now we take one more step and connect that diagram to a simple idea used in software: the finite state machine (FSM).

You do not need to be an expert in state machines to follow this chapter. We will use the same “Person Identification” example and translate it into plain language.

What Is a Finite State Machine

A finite state machine is a model of behavior. It describes a system that can be in one state at a time, and can move to another state when something happens.

Here is the entire concept in two simple statements:

• At any moment, the machine is in exactly one of a finite number of states.
• The machine changes state in response to external input (an event).

If this sounds familiar, it should. That is exactly how we described a business sub-process.

How a Sub-Process Becomes a State Machine

Look at the diagram again. Each rounded rectangle is a state where the sub-process waits. Nothing happens until a trigger occurs.

When a trigger occurs, the sub-process performs work and then ends up in a new state. This movement from one state to another is called a transition.

In business language, a transition is simply:

• A set of activities performed according to rules that moves the sub-process from the current state to a target state.

Some events do not change the state. In a diagram, this is often shown as an arrow that returns to the same state. In real life, it represents an action that happens without changing the overall situation.

Why This Matters

When we say that a business process (or sub-process) can be represented as a finite state machine, we are not changing the meaning of a business process. We are gaining a precise way to implement it.

A state machine gives us a clear structure:

• States (where the process waits)
• Triggers (events that start work)
• Transitions (the work that moves the process forward)
• Rules (decisions that choose outcomes)

Alternative Definition of a Business Process

A business process is a programmed finite state machine.

This definition is useful because it connects business language to software structure. It explains why state diagrams are not just drawings: they can become executable logic.

In the next chapter, we will look more closely at the two building blocks that make this work: states and how they are connected.

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