industrial//industrial data layer//OPC//OPC UA

**OPC Unified Architecture** is the modern evolution of OPC: platform independent, no COM/DCOM, no Windows requirement, with built-in security (certificates, encryption, authentication) and, above all, an **information model**: objects, variables, methods and hierarchies with semantics.

OPC Unified Architecture is the modern evolution of OPC: platform independent, no COM/DCOM, no Windows requirement, with built-in security (certificates, encryption, authentication) and, above all, an information model: objects, variables, methods and hierarchies with semantics.

Modbus: register 40123 = 72.4.

OPC UA: Boiler1 has a Temperature whose Value is 72.4, Unit is degrees Celsius, Quality is Good and Timestamp is such-and-such; Compressor_17 exposes Speed, Temperature, State, Manufacturer and a Start() method.

That richness is the difference between a number and a datum, and it is why OPC UA is central to digitalization: a consumer can browse a server and discover what exists, with units and types, instead of reading a register map.

It runs over TCP/IP and so over any stack, including 4G and radio at a remote station (protocol stack). Modern PLCs embed an OPC UA server; a legacy plant gets one from the edge gateway, which reads Modbus, HART and PROFIBUS and exposes them as OPC UA nodes.

Its natural partner rather than rival is MQTT in the plant: OPC UA describes and serves data, MQTT distributes it; a common pattern publishes OPC UA structured payloads over MQTT.