Another approach, used for example in the ConditionClass of Alarms (and with version 1.05.02 also in normal Events). The ConditionClassId Variable and also the ConditionSubClassId Variable are of DataType NodeId and point to specific ObjectTypes (either BaseConditionClassType or a subtype). This approach is actually more than an enumeration, as it allows the specialization of enumeration values in the ObjectType hierarchy. If such a specialization is required, it is recommended to use this approach.