Various information elements of a Condition are not considered to be states. However, a change in their value is considered important and supposed to trigger an Event Notification. These information elements are called ConditionVariable.
ConditionVariables are represented by a ConditionVariableType, formally defined in Table 4.
Table 4 – ConditionVariableType definition
|ValueRank||-2 (-2 = Any)|
Subtype of the BaseDataVariableType defined in OPC 10000-5.
SourceTimestamp indicates the time of the last change of the Value of this ConditionVariable. It shall be the same time that would be returned from the Read Service inside the DataValue structure for the ConditionVariable Value Attribute.