. OPC Unified Architecture Part 4: Services. Release 1.05.00. 2021 -10 -12. , OPC Foundation, 2021.

This document is the "Part 4: Services" specification for the OPC Unified Architecture (OPC UA) technology used in industrial automation systems. It defines a set of abstract Remote Procedure Calls (RPCs) that are implemented by OPC UA servers and invoked by clients. The document comprehensively explains service sets such as discovery, secure channel, session, node management, views, attributes, methods, monitored items, and subscriptions.