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Event Storming Overview

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Collaborative technique for discovering Ubiquitous Language through domain exploration

What is Event Storming?

Event Storming is a group of collaborative modeling techniques that help teams understand complex domains by visually mapping out key events. It is designed to help people from different parts of an organization create a shared understanding of the problem space they are going to work with.

Event Storming uses a game-like format with rules, a "board" (brown packing paper), and grammar (colored sticky notes). This collaborative approach surfaces the domain vocabulary through structured conversation.

Why Event Storming Matters for Specifications

Event Storming creates the foundation for all specifications work:

  • Discovers domain vocabulary that flows into Example Mapping and Gherkin
  • Surfaces terminology conflicts before they become specification problems
  • Identifies bounded contexts where different languages apply
  • Reveals business processes that need to be specified
  • Builds shared understanding across business and technical teams

How Event Storming Helps

Discovers Domain Vocabulary

Ubiquitous Language doesn't emerge spontaneously—it's discovered through collaborative domain exploration. Event Storming is a powerful technique for this discovery.

When domain experts explain processes, they use their natural vocabulary. When developers ask clarifying questions, misunderstandings emerge and get resolved.

Surfaces Critical Information

Event Storming workshops surface critical information for specifications:

Domain Events:

  • Things that happen in the business
  • Examples: "Order Placed", "Payment Received", "Approval Granted"
  • Become the foundation for Given/When/Then scenarios

Actors/Personas:

  • Who initiates or responds to events
  • Examples: "Customer", "Manager", "System Administrator"
  • Appear in user stories ("As a customer...")

Commands:

  • Actions that cause events
  • Examples: "Place Order", "Approve Request", "Cancel Subscription"
  • Become the "When" in scenarios

Policies:

  • Business rules that govern behavior
  • Examples: "Orders over $10,000 require manager approval"
  • Become acceptance criteria (Rule blocks)

Bounded Contexts:

  • Where different terminologies apply
  • Examples: "Customer" in Sales context vs Support context
  • Prevents terminology confusion in specifications

From Event Storming to Specifications

Event Storming → Example Mapping

Event Storming provides the vocabulary for Example Mapping workshops:

Event Storming discovered:

  • Domain event: "Order Approved"
  • Actor: "Manager"
  • Policy: "Large orders require approval"

Example Mapping applies this:

  • Yellow card: "As a manager, I want to approve large orders..."
  • Blue card: "Orders over $10,000 must be approved by a manager"
  • Green card: "Given an order of $15,000, when manager approves..."

See: Example Mapping for detailed workshop process.

Event Storming → Gherkin Specifications

Event Storming vocabulary flows directly into Gherkin:

Event Storming discovered:

  • Domain terms: "Order", "Manager", "Approved"
  • Process flow: Place order → Check amount → Require approval → Manager approves

Gherkin specification:

Feature: Order Approval Process

  Rule: Large orders require manager approval

    @ov
    Scenario: Manager approves large order
      Given an order with amount $15,000
      And the order status is "Awaiting Approval"
      When the manager approves the order
      Then the order status should be "Approved"
      And the order should be eligible for fulfillment

Notice: Every term comes from Event Storming—"order", "manager", "approved", "awaiting approval".

Maintaining Glossaries

During Event Storming: Use white definition stickies to capture term meanings

After Event Storming: Create a glossary document

Example glossary format:

# Domain Glossary: Order Management Context

**Order**: A customer request to purchase products
- Status values: "Pending", "Awaiting Approval", "Approved", "Fulfilled"
- Bounded context: Order Management

**Manager**: An employee with approval authority
- Can: Approve orders, reject orders, request more information
- Bounded context: Order Management

**Approved**: Business acceptance of an order
- Trigger: Manager approval action
- Result: Order eligible for fulfillment
- NOT the same as "Verified" (data correctness)

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