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Step 1 - Crowdsource events

The first step in any EventStorming session is crowdsourcing events. Individuals brainstorm events and write them down on orange sticky notes. To get started, think about the first and last events in your business domain.

As an example, when modeling "onboarding users" the first domain event could be name entered and the last event may be converted to active. There will be many more events between these starting and ending events. Everyone's job is to brainstorm events without worrying about naming them right, duplicates or ordering. Don't over-complicate it! Many people worry about getting things "right". What's most important at this phase is "doing."

Orange sticky notes represent domain events

However, this begs the question: what is an event? In EventStorming and event-driven architecture we define an event as:

Domain event

noun

  1. Something that a domain expert cares about.
  2. An immutable fact that has occurred in the past.

Events are written in the past tense. They are facts that have already occurred and cannot be changed. What constitutes a domain event is defined by you and your domain experts. What may be irrelevant in one business domain may be important in another.

Is a user scrolling the to bottom of a webpage a domain event? It depends. If you are operating in the domain of e-commerce, it's unlikely you may care when a user scrolls to the bottom of a page. However, if you're building a web analytics platform, a user moving to the bottom of the page may be very important. It's up to you and the other domain experts to define what is or is not a domain event.

Add a time constraint when starting the workshop and creating events. 10 or 15 minutes will usually suffice to get started. What's most important is participation from everyone and building momentum. When doing a Big Picture session more time isn't better. With more time, people may feel like they need to go into more detail. Remember that a Big Picture session is just that...big picture! It can be a challenge but try to save the details for later.

Once the team has created some events it's time to sequence them. Read the next section to learn how to run this next phase.