Events

GreenBus Events are notifications of meaningful occurrences or changes of state in the system. They can be used to both monitor status is real-time and provide audit logs of system history.

Events are created either by the core components directly, or by system participants using the GreenBus APIs.

While any process may post an Event to the Event service, the ultimate representation of the Event is centrally configured. Events are created with an event type, which (may) correspond to an entry in the event configuration. The event configuration defines they key attributes of Events of a given type and determines whether the Event also implies an Alarm condition.

The following table describes common attributes for Events:

Attribute	Description
Message	A human readable message describing the Event.
Time	Time the Event was entered into the system.
Device time	Time of occurrence for the underlying condition that caused the Event to be published.
Severity	Severity ranking for the Event. 1 is the most severe. The number of severity levels is configurable.
Subsystem	Identifier for the process that authored this event.
Agent	The system Agent responsible for creating the Event.
Object	The object in the system model the Event is most closely related to.

Alarms

GreenBus Alarms are notifications of system occurrences which require operator intervention or explicit acknowledgement. All Alarms are associated with an Event, but not all Events cause an Alarm.

In contrast to Events, Alarms have persistent, changeable state. The three principal Alarm states are unacknowledged, acknowledged, and removed. The transitions between these states constitute the alarm lifecycle. Additionally, unacknowledged Alarms may be marked as silent to advise human interfaces on how to represent them.