OPC UA Companion Specification

Defines a formal, object-oriented type system for a particular industry vertical. This model extends the base OPC UA specification with domain-specific ObjectTypes, VariableTypes, and ReferenceTypes.

• Standardizes the representation of physical entities like a 'CNC Axis' or 'Robot Arm'
• Defines mandatory and optional properties, such as CurrentPosition or MotorTemperature
• Enables a server to self-describe its capabilities to any generic OPC UA client

Ensures that the meaning of data is unambiguous and automatically understood by all connected systems. This moves beyond simple data transfer to shared understanding.

• Uses OPC UA Nodeset files to formally define the semantics of each data point
• A Temperature value from Vendor A's sensor is semantically identical to Vendor B's
• Eliminates the need for manual signal mapping and custom driver development

A Companion Specification is created and governed by a joint working group of industry competitors, ensuring no single vendor's proprietary format becomes the standard.

• Developed under the OPC Foundation umbrella by organizations like VDMA or OMAC
• Prevents vendor lock-in by making the interface public and royalty-free
• Allows end-users to mix and match best-in-class equipment on a single unified network

Inherits the robust, defense-in-depth security architecture of the OPC UA framework, which is mandatory for industrial communication.

• Supports X.509 certificate exchange for application and user authentication
• Provides message signing and encryption at the transport layer
• Defines a role-based access control model to restrict which users can read or write specific nodes in the information model

Formalizes the operational states and permitted transitions of a physical asset, such as a machine tool or robot. This is critical for supervisory control.

• Defines a Finite State Machine with states like Idle, Executing, Held, and Aborted
• Standardizes the method calls to trigger transitions, e.g., Start, Hold, Reset
• Enables a single supervisory system to orchestrate a heterogeneous production line with a unified state model

Allows system integrators to design and configure automation networks before physical hardware is connected, using the specification as a contract.

• A client can query a server for its TypeDefinition to discover its capabilities at runtime
• Engineering tools can import the specification's Nodeset2.xml file to pre-populate project databases
• Supports Virtual Commissioning by allowing a simulated server to present the exact same interface as the real device

The ability of two systems to exchange data with unambiguous, shared meaning. This is the core problem solved by Companion Specifications.

• Syntactic interoperability: Agreed data formats (XML, JSON)
• Semantic interoperability: Agreed meaning ("Is 'Temperature' in Celsius or Fahrenheit? Is it ambient or process temperature?")
• Companion Specs achieve this through formal ontologies and standardized type definitions, ensuring a robot from Vendor A understands a command from Controller B without custom mapping code.

An open, XML-based data exchange format for storing and transferring engineering data between heterogeneous software tools. It is the static design-time counterpart to OPC UA's runtime communication.

• Stores plant topology, geometry, kinematics, and logic
• Complements OPC UA by providing the engineering context that gives runtime data its meaning
• Often used to generate the initial OPC UA information model for a production cell

The practice of testing and validating industrial control logic against a simulated digital model before physical deployment. OPC UA Companion Specifications accelerate this process by providing a standardized interface to the virtual controller.

• The simulation tool connects to the virtual PLC via the same OPC UA interface as the real hardware
• Eliminates the need for custom signal mapping between simulation and control
• Reduces on-site commissioning time by up to 80% by catching logic errors in the virtual environment

A centralized software infrastructure that manages, runs, and visualizes multiple digital twins. OPC UA Companion Specifications serve as the standardized ingestion protocol for these platforms.

• A Twin Registry uses the Companion Spec's type system to discover and classify new assets automatically
• Real-time telemetry streams in via the standardized OPC UA Pub/Sub or Client/Server models
• Enables vendor-agnostic dashboards that can visualize any compliant asset without custom drivers

An extension to the OPC UA framework that enables connectionless, one-to-many communication patterns. While traditional Client/Server is request-response, Pub/Sub allows a sensor to broadcast data to multiple subscribers simultaneously.

• Uses UDP multicast or broker-based protocols like MQTT and AMQP
• Companion Specifications define the DataSetMetaData so subscribers know the exact structure of published messages
• Critical for high-speed, deterministic data distribution across large-scale systems