Notes from Domain Driven Design: Complete Software Architecture Course.
Generic terms
Domain: Subject area around which the program is going to be built.
Domain Model: Conceptual object model representing different parts of the domain (both behaviour and data).
Bounded Context: Context to which a model can be applied.
Ubiquitous Language: Common domain language used within the team and in the code.
Building blocks
Entity: Object identified by a thread of continuity and/or its identity, rather than by its attributes.
Value: Object that has attributes, but no identity. It should be treated as immutable.
Aggregate: Collection of values and entities bound together by a root entity (Aggregate Root) that encapsulates them. External objects should not reference Aggregate Root members (it ensures consistency of changes made).
Domain Event: An event directly related with the domain.
Example
Name, Address are Values:
- no need to be identifiable
- won’t change
Customer is an Entity:
- uniquely identifiable
- may need to change over time
Hotel Room is an Entity:
- uniquely identifiable
Booking is an Aggregate:
- encapsulates Customer and Hotel Room entities
- could encapsulates other properties (e.g. booking date)
Booking Created is a Domain Event:
- event directly related to the Domain
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