Conditionsare used in specific application domains like Maintenance, System or Process. The ConditionClasshierarchy is used to specify domains and is orthogonal to the ConditionTypehierarchy. The ConditionClassId Propertyof the ConditionTypeis used to assign a Conditionto a ConditionClass. Clientscan use this Propertyto filter out essential classes. OPC UA defines the base ObjectTypefor all ConditionClassesand a set of common classes used across many industries. Figure 21informally describes the hierarchy of ConditionClass Typesdefined in this standard.

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Figure 21– ConditionClass type hierarchy

ConditionClassesare not representations of Objects in the underlying system and, therefore, only exist as Type Nodesin the Address Space.