The OPC UA Standards include provisions for auditing. Auditing is an important security and tracking concept. Audit records provide the “Who”, “When” and “What” information regarding user interactions with a system. These audit records are especially important when Alarmmanagement is considered. Alarmsare the typical instrument for providing information to a user that something needs the user’s attention. A record of how the user reacts to this information is required in many cases. Audit records are generated for all Methodcalls that affect the state of the system, for example, an Acknowledge Methodcall would generate an AuditConditionAcknowledgeEventType Event.
The standard AuditEventTypesdefined in OPC 10000-5already include the fields required for Conditionrelated audit records. To allow for filtering and grouping, this standard defines a number of sub-types of the AuditEventTypesbut without adding new fields to them.
This standard describes the AuditEventType thateach Methodis required to generate. For example, the Disable Methodhas an AlwaysGeneratesEvent Referenceto an AuditConditionEnableEventType. An Event of this type shall be generated for every invocation of the Method. The audit Event describes the user interaction with the system, in some cases this interaction may affect more than one Conditionor be related to more than one state.