The ErrorConditionsobject contains a list of currently pending error messages.

The basis for the processing of error messages is the Alarm and Condition Model from OPC UA, which is defined in IEC 62541-9:2015.

An error message is represented by an object of the type AlarmConditionTypeor by a type derived from it.

The AlarmConditionTypeand its base types define various states such as EnabledState, AckedStateor ActiveStateand further properties such as Severity, Message, Timeand SourceNode. The Retain Propertyindicates whether an error message is of interest to the client.

Changes to the status of an error message are supplied to the clients via Events. A client can request the current status for all error messages where Retain= true as an event via the ConditionRefreshmethod. Clients can thus request a list of pending error messages after establishment of a connection.

Clients can confirm error messages via Methodsin order, for example, to change the AckedStateof the error message.