The document discusses modeling domains and distributed systems. It recommends explicitly representing state transitions in domains. It also advocates separating commands from queries, using asynchronous context mapping, and storing events. Most queries and interactions between bounded contexts can tolerate relaxed consistency for improved scalability and availability. The domain model may differ from the client data model for screens. Getters and setters are considered an anti-pattern for domains.

1. Unleash Your Domain
Greg Young

2. Agenda
• The Issues
• The Breakthroughs
– Explicit State Representation
– Event Storage
– Command Query Separation
– Asynchronous Context Mapping
• Summary
• Questions

8. State transitions are an important part of our
problem space and should be modeled within
our domain.

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20. Data Storage
Domain Domain
Object Object
Application Services
Remote Facade
Send up DTO Request DTO
Status returned DTO returned
Client

21. DTO Sent Request DTO
Ack/Nak Response DTO returned
Send DTO Back to Show DTO on
Server Screen
User Interacts With
DTO

22. Map DTO from
Domain
Save Domain
Edit DTO in UI
Object(s)
Map Data from Send DTO to
DTO to Domain Server

23. Query Data
Save Domain
Build Commands
Object(s)
Domain Validates Send Commands
Commands to Domain

24. Data Storage
Domain Domain
Object Object Thin Read Layer (Direct to DTO)
Remote Facade
Application Services
Remote Facade
Message Sent Request DTO
Ack/Nak Response DTO returned
Client

25. Write (Command) Data Storage Read (Query)
Domain Domain
Object Object Thin Read Layer (Direct to DTO)
Remote Facade
Application Services
Remote Facade
Message Sent Request DTO
Ack/Nak Response DTO returned
Client

26. A single model cannot be appropriate for
reporting, searching, and transactional
behaviors…

29. The model that a client needs the data in a
distributed system is screen based and different
than the domain model.

31. Most queries can operate with relaxed
consistency…

32. Denormalizer
Data Storage ------------------- Data Storage
Anti
Corruption
Domain Domain
Object Object
Application Services Thin Read Layer (Direct to DTO)
Remote Facade Remote Facade
Client

34. Getters and Setters are a
domain anti-pattern.

38. Most Bounded Contexts can interact with
relaxed consistency.

40. Using relaxed consistency allows us to increase
our scalability and availability!

41. “Man acts as though he were the shaper and
master of language, while in fact it is language that
is the master of man.”

42. State transitions are an important part of our
problem space and should be modeled within
our domain.

43. Getters and Setters are a domain smell.

44. Most Bounded Contexts can interact with
relaxed consistency.

45. A single model cannot be appropriate for
reporting, searching, and transactional
behaviors…

46. Questions