This document provides an overview of key concepts in Domain-Driven Design (DDD) including the ubiquitous language, bounded contexts, value objects, entities, repositories, collections, mappers, identity maps, units of work, and services. It explains that DDD is a set of principles and patterns that help developers create elegant systems by focusing on the core domain and language of the business. It also emphasizes separating business processes into bounded contexts and using ubiquitous language consistently throughout the code.

1. Implementing DDD
Concepts in PHP
Steve Rhoades
Panasonic Avionics
http://github.com/steverhoades
@steverhoades
http://linkedin.com/in/steverhoades
http://stephenrhoades.com
Aleksey Khudyakov
Roave, LLC
http://github.com/Xerkus
http://roave.com
Special Thanks
Marco Pivetta, Roave LLC http://github.com/ocramius

2. Overview
• Ubiquitous Language
• Bounded Context
• Value Object
• Entity
• Repository
• Collection
• Mapper
• Identity Map
• Unit of Work
• Services

3. What is Domain Driven Design

4. Collection of principles and
patterns that help developers
craft elegant systems

5. Ubiquitous Language

6. Allows for precise communication
of ideas between stakeholders
and developers

7. Developers should speak the
language as well as include the
language in the code base

9. Bounded Context

10. Keep varying business processes
separated

11. Overlapping of business
concerns should communicate
through services

12. Value Object

13. An object that contains attributes
but does not have an identity

14. Value Objects are Immutable

16. Don’t forget behaviors!

18. Entity

19. An entity is an object in your
application that has an identity.

20. Anemic Entity anti-pattern

21. Look like Value Objects but
have identity

22. Lack behavior

25. Repository

26. A segregated interface that
utilizes the ubiquitous
language to hide the
infrastructure layer

27. Storage, Memory, Remote Service

31. Collections

34. Mapper (Data Mapper)

35. Used to pull Entity data
from persistence

36. Developers can create
custom Data Mappers
without affecting the rest of
the application

37. • Unit Test
• MongoDB
• Redis
• MySQL
• Oracle
• Web Services
• File System

40. Identity Map

41. Caches Entities in memory
to ensure there is only one
instance in memory at any
given time

42. Martin Fowler
P of EAA
READ THIS!

44. Services

45. Utilized when the natural
processing on an Entity or a
Value Object is no longer
valid

46. Domain Services should
not contain state

48. Application Services and
Domain Services are often
confused

49. Application Services
orchestrate demands from
a given use case or
workflow

50. Application Services
“should not” contain
business logic will make
calls to Domain and
Infrastructure services as
well as Entities

51. Helpful to think of an
Application Service as a
command object

52. Unit of Work
(example of Application Service)

53. Maintains a list of objects affected by a
business transaction and coordinates the
writing out of changes and the resolution
of concurrency
- Martin Fowler, P of EAA

55. Further Resources
• Domain Driven Design, Eric Evans
• Patterns of Enterprise Application Architecture,
Martin Fowler
• Applying Domain-Driven Design and Patterns,
Jimmy Nilsson
• Implementing Domain Driven Design, Vernon
Vaughn

56. Please Review
https://joind.in/9594