Conditions are used in specific application domains like Maintenance, System or Process. The ConditionClass hierarchy is used to specify domains and is orthogonal to the ConditionType hierarchy. The ConditionClassId Property of the ConditionType is used to assign a Condition to a ConditionClass. Clients can use this Property to filter out essential classes. OPC UA defines the base ObjectType for all ConditionClasses and a set of common classes used across many industries. Figure 23 informally describes the hierarchy of ConditionClass Types defined in this standard.

Figure 23 – ConditionClass type hierarchy

ConditionClasses are not representations of Objects in the underlying system and, therefore, only exist as Type Nodes in the Address Space.