OPC UA Fundamentals

Most important to understand how to model and access information are the OPC UA specifications Part 3 and 4. These two specifications are the key documents for the design and development of OPC UA applications. This part of the documentation provides an abstract of these fundamentals of the OPC Unified Architecture. See OPC UA Specifications for a complete list of OPC UA specifications.

OPC Unified Architecture Overview

The Address Space Model in UA Part 3 specifies the building blocks to expose instance and type information and thus the OPC UA meta model used to describe and expose information models and to build an OPC UA server address space.

The base information model specified in UA Part 5 provides the framework for all information models using OPC UA. It defines the following:

  • The entry points into the address space used by clients to navigate through the instances and types of an OPC UA server
  • The base types building the root for the different type hierarchies
  • The built-in but extensible types like object types and data types
  • The Server Object providing capability and diagnostic information.

The abstract UA Services defined in UA Part 4 represent the possible interactions between UA client and UA server applications. The client uses the Services to find and access information provided by the server. The Services are abstract because they are defining the information to be exchanged between UA applications but not the concrete representation on the wire and also not the concrete representation in an API used by the applications. The concrete representation in an API used for this SDK is defined by the ANSI C UA Stack.