## 5.7.3 Acknowledge Method

The Acknowledge Method is used to acknowledge an Event Notification for a Condition instance state where AckedState is False. Normally, the NodeId of the object instance is passed as the ObjectId to the Call Service. However, some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Acknowledge Method by specifying ConditionId as the ObjectId. The Method cannot be called with an ObjectId of the AcknowledgeableConditionType Node.

Signature

Acknowledge(
[in] ByteString EventId
[in] LocalizedText Comment
);


The parameters are defined in Table 29

Table 29 – Acknowledge parameters

Argument Description
EventId EventId identifying a particular Event Notification.
Only Event Notifications where AckedState/Id was False can be acknowledged.
Comment A localized text to be applied to the Condition.

Method result codes in Table 30 (defined in Call Service)

Table 30 – Acknowledge result codes

Result Code Description
Bad_MethodInvalid The method id does not refer to a method for the specified object or ConditionId.
Bad_EventIdUnknown See Table 103 for the description of this result code.
Bad_NodeIdInvalid Used to indicate that the specified ObjectId is not valid or that the Method was called on the ConditionType Node. See OPC 10000-4 for the general description of this result code.

A Server is responsible to ensure that each Event has a unique EventId. This allows Clients to identify and acknowledge a particular Event Notification.

The EventId identifies a specific Event Notification where a state to be acknowledged was reported. Acknowledgement and the optional comment will be applied to the state identified with the EventId. If the comment field is NULL (both locale and text are empty) it will be ignored and any existing comments will remain unchanged. If the comment is to be reset, an empty text with a locale shall be provided.

A valid EventId will result in an Event Notification where AckedState/Id is set to True and the Comment Property contains the text of the optional comment argument. If a previous state is acknowledged, the BranchId and all Condition values of this branch will be reported. Table 31 specifies the AddressSpace representation for the Acknowledge Method.

Table 31 – Acknowledge Method AddressSpace definition

Attribute Value
BrowseName Acknowledge
References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasProperty Variable InputArguments Argument[] PropertyType Mandatory
AlwaysGeneratesEvent ObjectType AuditConditionAcknowledge
EventType
Defined in 5.10.5