IEC 62541-5.2015 defines the Information Model of the OPC Unified Architecture. The Information Model describes standardised Nodes of a Server's AddressSpace. These Nodes are standardised types as well as standardised instances used for diagnostics or as entry points to server-specific Nodes. This second edition cancels and replaces the first edition published in 2011 and constitutes a technical revision. This edition includes the following changes: - Defined ProgressEventType; - Defined DataType called BitFieldMaskDataType; - Delete Property SamplingRateCount in ServerDiagnosticSummaryDataType; - Added the Property "EffectiveTransitionTime" to TransitionVariableType; - Introduced VariableType OptionSetType; - Added a new EventType called SystemStatusChangeEventType; - Added properties to ServerCapabilitiesType. Added an object for operation limits. Added type OperationLimitsType containing that information; - Added SecureChannelId to AuditActivateSessionEventType; - Added normative Annex C defining FileType and Methods; - Added a Method GetMonitoredItems on ServerType; - Removed the concept of ModelParent. Added meta data for namespaces in ServerType and created types for managing that. Added representations for ModellingRules OptionalPlaceholder and MandatoryPlaceholder; - Added new types NonTransparentNetworkRedundancyType, NetworkGroupDataType and EndpointUrlListDataType.