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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

Attribute		Value
BrowseName		ConditionVariableType
DataType		BaseDataType
ValueRank		-2 (-2 = Any)
IsAbstract		False
References	NodeClass		BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the BaseDataVariableType defined in OPC 10000-5.
HasProperty	Variable		SourceTimestamp	UtcTime	PropertyType	Mandatory

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.