ZendCon 2011 UnCon Domain-Driven Design
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The document discusses domain-driven design (DDD), emphasizing the importance of collaboration between domain experts and software practitioners. It outlines core concepts such as modeling, bounded contexts, entities, value objects, aggregates, and domain events, while stressing that complexity lies within the domain rather than technology. It also highlights the need for clear communication and understanding in establishing effective software solutions based on core domains.
![Domain Event
• something important that happens within the domain that
may lead to a state change in a domain object
• current state can be computed by looking at all currently
known domain events (a.k.a. event sourcing[1])
1. http://martinfowler.com/eaaDev/EventSourcing.html](https://image.slidesharecdn.com/zendcon-2011-ddd-111018164225-phpapp01/85/ZendCon-2011-UnCon-Domain-Driven-Design-35-320.jpg)
![Domain Event
• something important that happens within the domain that
may lead to a state change in a domain object
• current state can be computed by looking at all currently
known domain events (a.k.a. event sourcing[1])
• domain events can trigger other domain events (e.g. three
strikes triggers an out)
1. http://martinfowler.com/eaaDev/EventSourcing.html](https://image.slidesharecdn.com/zendcon-2011-ddd-111018164225-phpapp01/85/ZendCon-2011-UnCon-Domain-Driven-Design-36-320.jpg)
ZendCon 2011 UnCon Domain-Driven Design
- 1. Domain-Driven Design A Collaboration Between Domain Experts and Software Practitioners
- 2. The Book http://domaindrivendesign.org/books/evans_2003
- 3. do·main dōˈmān n. a sphere of knowledge, in uence, or activity "domain." Merriam-Webster.com. 2011. http://www.merriam-webster.com/dictionary/domain (17 October 2011).
- 4. Core Domain
- 5. Core Domain • complexity is in the domain, not the technology
- 6. Core Domain • complexity is in the domain, not the technology • let technology play a supporting role
- 7. Core Domain • complexity is in the domain, not the technology • let technology play a supporting role • uncover your core domain and distill this core
- 8. The Model* *In domain-driven design, the model is not the classes or objects representing concepts within the model.
- 9. The Model* • a model is a tool for solving speci c problems within a domain *In domain-driven design, the model is not the classes or objects representing concepts within the model.
- 10. The Model* • a model is a tool for solving speci c problems within a domain • “the map is not the territory” —Alfred Korzybski *In domain-driven design, the model is not the classes or objects representing concepts within the model.
- 11. The Model* • a model is a tool for solving speci c problems within a domain • “the map is not the territory” —Alfred Korzybski • collaborative explore the model with both domain experts and software practitioners *In domain-driven design, the model is not the classes or objects representing concepts within the model.
- 12. Bounded Context
- 13. Bounded Context • there are always multiple models
- 14. Bounded Context • there are always multiple models • explicitly de ne a bounded context to which a model applies
- 15. Bounded Context • there are always multiple models • explicitly de ne a bounded context to which a model applies • speak a ubiquitous language within a bounded context
- 17. Building Blocks
- 18. Entity
- 19. Entity • de ned by a thread of continuity and identity
- 20. Entity • de ned by a thread of continuity and identity • only responsibilities should be around identity and life cycle
- 21. Entity • de ned by a thread of continuity and identity • only responsibilities should be around identity and life cycle • may be composed of other entities and/or value objects
- 22. Value Object
- 23. Value Object • de ned by its encapsulated attributes
- 24. Value Object • de ned by its encapsulated attributes • treat value objects as immutable
- 25. Value Object • de ned by its encapsulated attributes • treat value objects as immutable • delegate business logic to value objects
- 26. De ning an object as an entity or a value object is context-dependent.
- 27. Aggregate
- 28. Aggregate • a group of related entities and value objects
- 29. Aggregate • a group of related entities and value objects • useful when de ning transaction, distribution and concurrency boundaries
- 30. Aggregate • a group of related entities and value objects • useful when de ning transaction, distribution and concurrency boundaries • designate one entity as the aggregate root
- 31. Aggregate • a group of related entities and value objects • useful when de ning transaction, distribution and concurrency boundaries • designate one entity as the aggregate root • allow external references to only the aggregate root
- 32. Aggregate • a group of related entities and value objects • useful when de ning transaction, distribution and concurrency boundaries • designate one entity as the aggregate root • allow external references to only the aggregate root • delegate persistence of an aggregate root to a repository
- 33. Domain Event 1. http://martinfowler.com/eaaDev/EventSourcing.html
- 34. Domain Event • something important that happens within the domain that may lead to a state change in a domain object 1. http://martinfowler.com/eaaDev/EventSourcing.html
- 35. Domain Event • something important that happens within the domain that may lead to a state change in a domain object • current state can be computed by looking at all currently known domain events (a.k.a. event sourcing[1]) 1. http://martinfowler.com/eaaDev/EventSourcing.html
- 36. Domain Event • something important that happens within the domain that may lead to a state change in a domain object • current state can be computed by looking at all currently known domain events (a.k.a. event sourcing[1]) • domain events can trigger other domain events (e.g. three strikes triggers an out) 1. http://martinfowler.com/eaaDev/EventSourcing.html
- 37. Supple Design
- 39. Closure of Operations • have a method on a value object that returns an instance of the same type of value object
- 40. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object
- 41. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object • example: 2 + 3 = 5
- 42. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object • example: 2 + 3 = 5 • “2” is a value object of type number
- 43. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object • example: 2 + 3 = 5 • “2” is a value object of type number • number has an add method
- 44. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object • example: 2 + 3 = 5 • “2” is a value object of type number • number has an add method • add method accepts an argument of type number
- 45. Closure of Operations • have a method on a value object that returns an instance of the same type of value object • any method arguments should also be the same type as the value object • example: 2 + 3 = 5 • “2” is a value object of type number • number has an add method • add method accepts an argument of type number • add method returns a number
- 46. Other Techniques • intention-revealing interfaces • side-effect free functions • assertions
- 47. Strategic Design
- 48. Context Map
- 49. Context Map • draw a context map of the current bounded contexts
- 50. Context Map • draw a context map of the current bounded contexts • map what actually exists—not what you wish existed!
- 51. Context Map • draw a context map of the current bounded contexts • map what actually exists—not what you wish existed! • identify relationships between contexts
- 52. Relationship Patterns customer/ anticorruption partnership supplier layer shared kernel big ball of separate ways mud open host conformist published service language
- 53. Distillation
- 54. Multiple Models
- 55. Multiple Models • there are always multiple models
- 56. Multiple Models • there are always multiple models • a model my represent:
- 57. Multiple Models • there are always multiple models • a model my represent: • your core domain
- 58. Multiple Models • there are always multiple models • a model my represent: • your core domain • a supporting domain
- 59. Multiple Models • there are always multiple models • a model my represent: • your core domain • a supporting domain • a generic subdomain
- 60. Multiple Models • there are always multiple models • a model my represent: • your core domain • a supporting domain • a generic subdomain • focus your modeling efforts on the core domain
- 61. Identifying the Core Domain Ask organizational leaders and domain experts: • What keeps you awake at night? • What makes your system worth writing? • Why not buy it off the shelf? • Why not outsource it?
- 62. Don’t settle on not having access to a domain expert!
- 63. Thank You @BradleyHolt http://bradley-holt.com http://joind.in/4003 Copyright © 2011 Bradley Holt. All rights reserved.
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