Event Source

An event source can be viewed as instance grouping together all state changes to form a story for the particular entity in your domain. Each state change is represented as an event. With each event being completely autonomous and representing a just its part of the truth, the event source identifier is (EventSourceId) what what binds it together.

For instance, take the notion of a person. What identifies the person uniquely is in many systems the social security number assigned by the government for all residents. All state changes relevant for an instance of a person should be identified by this unique identifier, this is what we call an event source id.

It can be compared to the primary key often used in database modelling.

When events are appended in Chronicle, you'll see that the first argument is the EventSourceId.