Table C.1 lists EEMUA terms and how OPC UA terms map to them.

Table C.1 – EEMUA Terms



EEMUA Definition


Acknowledged = True

An Alarm is accepted when the Operator has indicated awareness of its presence.

In OPC UA this can be accomplished with the Acknowledge Method.

Active Alarm

Active = True

An Alarm Condition which is on (i.e. limit has been exceeded and Condition continues to exist).

Alarm Message

Message Property (defined in 10000-5.)

Test information presented to the Operator that describes the Alarm Condition.

Alarm Priority

Severity Property (defined in 10000-5.)

The ranking of Alarms by severity and response time.



A lower priority Notification than an Alarm that has no serious consequence if ignored or missed. In some Industries also referred to as a Prompt or Warning”.

No direct mapping! In UA the concept of Alerts can be accomplished by the use of severity. E.g., Alarms that have a severity below 50 may be considered as Alerts.


Active = False

An Alarm state that indicates the Condition has returned to normal.


Enabled = False

An Alarm is disabled when the system is configured such that the Alarm will not be generated even though the base Alarm Condition is present.



A request from the control system that the Operator perform some process action that the system cannot perform or that requires Operator authority to perform.


Active = True

An Alarm is Raised or initiated when the Condition creating the Alarm has occurred.



A ‘release’ is a facility that can be applied to a standing (UA = active) Alarm in a similar way to which Shelving is applied. A released Alarm is temporarily removed from the Alarm list and put on the shelf. There is no indication to the Operator when the Alarm clears, but it is taken off the shelf. Hence, when the Alarm is raised again it appears on the Alarm list in the normal way.


Retain = False

An Alarm is Reset when it is in a state that can be removed from the Display list.

OPC UA includes Retain flag which as part of its definition states: “when a Client receives an Event with the Retain flag set to False, the Client should consider this as a Condition/Branch that is no longer of interest, in the case of a “current Alarm display” the Condition/Branch would be removed from the display”



Shelving is a facility where the Operator is able to temporarily prevent an Alarm from being displayed to the Operator when it is causing the Operator a nuisance. A Shelved Alarm will be removed from the list and will not re-annunciate until un-shelved.


Active = True

An Alarm is Standing whilst the Condition persists (Raised and Standing are often used interchangeably).



An Alarm is suppressed when logical criteria are applied to determine that the Alarm should not occur, even though the base Alarm Condition (e.g. Alarm setting exceeded) is present.


Acknowledged = False

An Alarm is accepted when the Operator has indicated awareness of its presence. It is unaccepted until this has been done.