A deep dive into the technical building blocks of your domain model… We’ll cover Domain-Driven Design patterns like entities, value objects, repositories and domain events. Besides the basics, we’ll cover in detail different guidelines for modelling your aggregates. All of this is called ‘tactical DDD’ and it might just turn out to be about the fundamentals of object-oriented programming too! This workshop will lead you straight to the core of programming and ways in which you can improve your applications in general.

1. TACTICAL DDD
Just better OOP?
Matthias Noback
@matthiasnoback

2. matthiasnoback/
tactical-ddd-workshop
Clone from GitHub
Follow the instructions in README.md

3. TACTICAL DDD
As opposed to...

4. STRATEGIC DDD
The big picture
Ubiquitous language
Domain and subdomains
Bounded contexts
Context mapping
Collaboration
Discovery

5. TACTICAL DDD
Design patterns
Aggregate
Entity
Value object
Repository
Domain service
Factory

6. TACTICAL DDD
Its concerns
Performance
Reliability
Data integrity
Insight

7. DDD
Scaling your domain model
Keep it consistent
Keep it manageable
Make it perform well
Ubiquitous language
Bounded contexts
Aggregates

8. ENTITIES
Change & identity
Identity
Provided by user, application or persistence mechanism
Repository encapsulates identity generation
Surrogate identity
Mutability & individuality
Validation & consistency (encapsulation)

9. ENTITIES
Checklist
Does the object need to be retrieved from a repository by its
unique identity?
Does the object need to track changes?
Are two instances equivalent if they have the same identity?

10. VALUE OBJECTS
Properties
Descriptive
Immutable
Conceptual whole (composite)
Replaceable
Not identifiable but comparable
Side-effect free behaviors

11. VALUE OBJECTS
Checklist
Is it irrelevant which exact instance of the object is used?
Can the object be replaced, instead of modified?
Are two objects of the same type equal if their properties
contain equal values?

12. assignment/01.md
Entities and value objects

13. AGGREGATES
Consistency
Consistency boundary
Transactional consistency
Eventual consistency

14. “When examining the use case (or
story), ask whether it's the job of the
user executing the use case to make
the data consistent.

15. AGGREGATES
Rules of thumb
Small aggregates
Reference aggregates by identity
Use eventual consistency

16. AGGREGATES
Implementation
Root entity with unique identity
Favor value object parts
Use Law of Demeter and Tell, Don't Ask
Optimistic concurrency
Avoid dependency injection and references to static services

17. assignment/02.md
Extract an aggregate

18. DOMAIN EVENTS
Messages
Immutable
Relation with commands
Authoritative
Sufficient data

19. assignment/03.md
Domain events

20. REPOSITORIES
Persistence
Collection or persistence oriented
Persistence implementation
Unit of Work, change set calculation
Event-sourcing
Reconstitution
Querying

21. ASSIGNMENT/04.MD
An aggregate repository with an event store
Feedback? https://joind.in/talk/e8a3a

22. APPLICATION SERVICES
Clients of the domain model
Task coordination of use case flows
Transaction control
No business domain logic

23. assignment/05.md
Application services

24. THAT'S IT!
Thanks
Feedback? https://joind.in/talk/e8a3a

25. Feedback? https://joind.in/talk/e8a3a

26. Feedback? https://joind.in/talk/e8a3a