Maintenance activities can be classified into different categories. This specification uses the mechanism of the ConditionClassId defined for conditions in OPC 10000-9, for such a classification of maintenance activities. In the following, specific subtypes of MaintenanceConditionClassType are defined, that should be used as ConditionClassId for specific maintenance activities. Other companion specifications and vendors might add additional subtypes of MaintenanceConditionClassType and might inherit from the types defined in this specification.