What Event Modeling is
An event model tells a business process as a story of facts on a timeline.
After this page, you can:
- say in one sentence what an event model shows
- name the five parts of the basic flow, in order
- explain why you model the work before you think about software
A story on a timeline
An event model tells how a business works. You read it from left to right, like a comic strip. Each step shows a fact that happened. For example, a pet clinic added an appointment.
A fact is something that already happened. A fact does not change later. The model shows three more things around each fact:
- The intent that caused the fact. For example, a staff member wants to add an appointment.
- The information that people see after the fact. For example, the calendar.
- The people or machines that look at this information and then act.
Try first: a pet clinic books a visit by phone. Name two facts that the clinic can write down after the call.
Show the answer
Two good answers are Owner Registered and Appointment Added. Both names use the past tense. Both say what happened. Neither says what someone wants.
Start without software
Model the work as people do it without a computer. Ask three questions:
- How do people do this work on paper?
- Who acts, and what starts each action?
- What must the person know before the action?
Leave out each step that exists only because of software. A loading spinner, a cache refresh, and a session check are not business steps. They do not belong on the timeline.
The basic flow
Every model follows the same flow. Read it from left to right:
The table gives the meaning of each part. The examples come from a pet clinic. This guide uses the same clinic on every page.
| Part | What it is | Example |
|---|---|---|
| Screen | What a person sees and acts on. | The form that schedules an appointment. |
| Command | An intent to change something. The system can refuse it. | Add Appointment |
| Event | A fact that happened because a Command worked. | Appointment Added |
| Read Model | An answer that the system builds from Events. | Calendar: which appointments are on the calendar? |
| Screen | Shows the answer, so the person can decide the next step. | The calendar page. |
A machine can start a Command in place of a person. That machine step is an Automation. You meet it on page 2.
Cause comes before effect
The order of the steps must make causal sense. Four rules keep it that way:
- Every Event comes from one Command.
- Every Command has one reason. The reason is a Screen, where a person decides, or an Automation, where the system reacts.
- A story starts with a Read Model that feeds a Screen, or with an Automation that reacts to an Event that exists. It does not start with a Command that has no reason.
- Two Commands in a row need a trigger between them. If nothing triggers the second Command, the model has a gap.
Build first, then review
You work in two modes. Do not mix them in one pass. The method calls them Modeling Mode and Critic Mode.
| Mode | What you do | How you act |
|---|---|---|
| Build | Brainstorm, order, sketch, and write the model. | Capture the process as fully as you can. Note a small mistake and move on. |
| Review | Check what the model holds. | Apply every rule. Report each problem. Do not fix a problem in silence. |
A build pass is not the time for a full audit. A review pass is not the time to add missing parts. In a review, you write down what is missing.
Check yourself
Answer each question in your head first. Then open the answer.
Which name is a fact that happened: Add Appointment, Appointment Added, or Show Calendar?
Answer
Appointment Added. It uses the past tense. Add Appointment is a Command, which is an intent. Show Calendar is a question that a Read Model answers.
A model has the Command Add Appointment. Nothing starts it. What is wrong?
Answer
Every Command needs one reason. Add the Screen where staff add the appointment, or the Automation that adds it.
A team puts a loading spinner on the timeline. What do you do?
Answer
Remove it. A spinner exists only because of software. It is not a business step.
Remember:
- A model is a story of facts on a timeline, read from left to right.
- The basic flow is Screen, Command, Event, Read Model, Screen.
- Model the work without software first.
- Build the model in one pass and review it in another.