Aggregate - MerrionComputing/CQRSAzure GitHub Wiki

An aggregate is any business meaningful thing that is uniquely identifiable. (This is somewhat analogous to an Entity in a relational model.)

An aggregate has two properties - the aggregate type (which is conceptually similar to a class definition or table definition) and the aggregate instance which is an uniquely identifiable instance of that type.

An aggregate is something to which an event can occur and when this happens the event detail is appended to the end of the event stream for that aggregate instance.

In this implementation we do not store any data for an aggregate excepting identifying data - how the aggregate is uniquely identified. This is because all other attributes of an aggregate instance can change over time when events occur to it.

Example

From the CQRS Farm Demo Example we could have aggregate types for, for example, "Cow", "Field", "Tractor" etc. and have instances of "Cow" identified by ear tag numbers (102, 103, 104 etc.)