IEC 62541-9:2015 specifies the representation of Alarms and Conditions in the OPC Unified Architecture. Included is the Information Model representation of Alarms and Conditions in the OPC UA address space. This second edition cancels and replaces the first edition published in 2012 and constitutes a technical revision. This edition includes the following changes: - added section to describe expect behaviour for A&C servers and the associated information model in the case of redundancy or communication faults; - changed the DialogConditionType to be not abstract since it is expect that instance of this type will exist in the system; - updated ConditionRefresh Method to allow the use of the well know NodeIds associated with the types for the MethodId and ConditionId instead of requiring the call to use only the MethodId and ConditionId that is part of an instance; - Fixed ExclusiveLimitStateMachineType and ShelvedStatemachineType to be sub-types of FinitStateMachineType not StateMachineType.