An event is an individual happening, taking place at a given moment. Each event is indivisible and instantaneous. The event execution is defined by its event type.

Discreteness is a property of an event stating that the changes in the state could be counted (i.e. changes are discrete in the mathematical definition).

Each event defines following outputs:
 * a simulation state update regarding the event that happened.
 * a list of events that should be inserted in the future events.
 * some events that are postponed.
 * some events that are cancelled.

[See the entity](docs/archi/event_entity.png)

An event type: The event type is used to define what event execution will happen.

Event structure is a map with at least two keys:
* `type` a the event type as found in `evt-type-priority`.
* `date` as a date.

An event execution is updating the state and may trigger some new events to be added in the future events. The result of the event execution could be dependent on the state or random variable.

* [See entity](docs/archi/event_execution.png)

What is returned by an event.

A scheduler snapshot is a consistent set of data for the scheduler.
It is containing the simulation state, past events and future events and iteration number scheduler snapshot is identified with an id property and is related to exactly one date. Past and Future events are sorted collection of events.

Remarks:
* An entity using the scheduler snapshot should not access past or future events to have some information on the state the simulation.

  * [See entity](docs/archi/snapshot_entity.png)