Modelling complex business domains with events

Modelling complex business domains with events

Ben Smith

Overview

1. Introduction to domain events
2. Modelling complex business processes with events
3. Implementing our model in Elixir

What are domain events?

Domain event

• Record of something that took place in a business domain
• An immutable, historical fact
• Named in the past tense using the language of the business
• Examples:
  • Item Added To Cart
  • Checkout Completed
  • Payment Taken
  • Order Dispatched

Event-driven systems

• Event notification
  • Publish notification domain events to other systems
• Event-carried state transfer
  • Publish enriched domain events containing details of any changes
• Event sourcing
  • Record all changes to a system as internal domain events
  • Current state is (re)built from events

See Martin Fowler's What do you mean by “Event-Driven”?

How do I model with events?

1. Big picture
   • Knowledge or learning is the most valuable outcome
   • Identify bounded contexts and/or service boundaries
2. Design level
   • Design a solution to a specific business problem
   • Desired outcome is a robust candidate solution

www.eventstorming.com

Big picture EventStorming

Design level EventStorming

Modelling an online auction system

How do I implement the model in Elixir?

Get in touch

• ben@10consulting.com
• 10consulting.com