Comment, severity and quality are important elements of Conditions and any change to them will cause Event Notifications.
The Severity of a Condition is inherited from the base Event model defined in OPC 10000-5. It indicates the urgency of the Condition and is also commonly called ‘priority’, especially in relation to Alarms in the ProcessConditionClassType.
A Comment is a user generated string that is to be associated with a certain state of a Condition.
Quality refers to the quality of the data value(s) upon which this Condition is based. Since a Condition is usually based on one or more Variables, the Condition inherits the quality of these Variables. E.g., if the process value is “Uncertain”, the “Level Alarm” Condition is also questionable. If more than one variable is represented by a given condition or if the condition is from an underlining system and no direct mapping to a variable is available, it is up to the application to determine what quality is displayed as part of the condition.