OPC UA gives machines a common language. But a common language isn’t enough if everyone uses different vocabulary. A packaging machine and a robot arm both “speak” OPC UA — but how they describe themselves, their data, and their capabilities needs to follow a shared standard too.
That’s what companion specifications do. They define standardized data models for specific industries and device types, built on top of OPC UA’s core framework. They’re the reason a packaging machine from Vendor A describes itself the same way as one from Vendor B — making integration plug-and-play instead of a custom engineering project.
This guide explains what companion specifications are, how they work, which ones exist, and how to use them in your projects.
Table of Contents
What Is a Companion Specification?
A companion specification is a standardized information model written using OPC UA’s modeling language. It defines how a specific type of device or industry should expose its data through OPC UA.
Think of it this way. OPC UA’s core standard (IEC 62541) gives you the grammar — nodes, references, types, attributes, methods. A companion specification gives you the vocabulary — the specific words and structures that a CNC machine, a robot, or a packaging line should use to describe itself.
Without companion specifications, every vendor would invent their own OPC UA data model. Your Siemens robot would organize its data one way, your FANUC robot another way, and your ABB robot yet another way. You’d need custom integration for each vendor — defeating the purpose of having a standard in the first place.
With a companion specification like OPC UA for Robotics, all three robots expose the same types of data in the same structure. Your MES, SCADA, or analytics platform connects to any of them with zero vendor-specific configuration.
How They’re Built
Companion specifications are built on top of OPC UA’s type system. They define new ObjectTypes, VariableTypes, and ReferenceTypes that extend the base OPC UA model.
For example, the Robotics companion specification defines a MotionDeviceSystemType. Any robot that implements this type will expose its axes, controllers, safety states, and motion device information in a standardized structure. A client that understands MotionDeviceSystemType can work with any robot from any vendor that implements the spec.
Each companion specification comes with two key deliverables: a human-readable document that describes the information model, its types, and how they should be used, and a machine-readable nodeset file (XML) that OPC UA servers can import directly to implement the model.
The nodeset files are freely available from the OPC Foundation’s GitHub repository and their cloud library.
Who Creates Them?
Companion specifications are created through three main channels.
Joint working groups
The most common approach. An industry association partners with the OPC Foundation to form a joint working group. Domain experts from member companies define the information model, the OPC Foundation ensures it follows OPC UA best practices, and the result is published as an official specification.
The VDMA (German Mechanical Engineering Industry Association) is the most active organization, coordinating roughly 40 working groups across different industries. Other organizations include EUROMAP (plastics and rubber machinery), VDW (machine tools), AIM (auto identification), and many more.
Internal OPC Foundation groups
Some specifications are created by OPC Foundation working groups alone. These tend to be cross-industry foundational models — like OPC UA for Devices (Part 100), which provides base types that many industry-specific companion specs build upon.
External organizations
Standards bodies and industry consortiums can also create companion specifications independently. As long as the specification follows OPC UA modeling rules and passes the OPC Foundation’s release process, it can be published as an official companion specification.
Key Companion Specifications by Industry
Over 60 companion specifications exist today, with more in development. Here are the most significant ones organized by industry.
Plastics and Rubber Machinery (EUROMAP)
The EUROMAP series is one of the most mature sets of companion specifications. EUROMAP 83 provides the base types that all other EUROMAP specs build on. EUROMAP 77 covers injection molding machines connecting to MES systems. EUROMAP 79 handles the interface between injection molding machines and robots. EUROMAP 82.x defines connections between injection molding machines and peripheral devices like temperature controllers. EUROMAP 84 covers extrusion lines. EUROMAP 85 addresses blow molding machines.
These specs replaced the older file-based EUROMAP 63 standard with real-time OPC UA communication — a major upgrade for the plastics industry.
Robotics
OPC UA for Robotics (VDMA 40010) provides a standardized information model for any type of robot — industrial robots, mobile robots, collaborative robots, multi-arm systems, and more. Part 1 covers the basic description of a motion device system and pushes condition data upward to MES or cloud systems. Further parts cover additional use cases like configuration and control.
Machine Vision
OPC UA for Machine Vision (VDMA 40100) defines a generic model for vision systems, from simple sensors to complex multi-camera inspection stations. It abstracts machine vision behavior through a state machine concept and handles recipe management, configuration, and results in a standard way.
Machine Tools
OPC UA for Machine Tools was developed by the VDW (German Machine Tool Builders’ Association) and forms the backbone of the umati initiative — a universal machine tool interface. It covers machine identification, status monitoring, job management, and production data. The goal is that any CNC machine from any manufacturer presents the same basic data to MES and monitoring systems.
Packaging (PackML)
PackML (Packaging Machine Language) defines standard state machines and data for packaging equipment. The OPC UA companion specification maps PackML concepts to OPC UA types, enabling standardized communication between packaging lines and enterprise systems in the food, beverage, and consumer goods industries.
Food and Beverage (Weihenstephan Standards)
The Weihenstephan Standards define communication interfaces for machines in food and beverage production. The OPC UA companion specifications cover different domains — WS Food, WS Pack, WS Bake, WS Brew — with data models tailored to each segment’s unique requirements.
Weighing Technology
OPC UA for Weighing Systems covers the transport of condition data from weighing instruments to MES and higher-level systems. It handles diagnostic information and allows setting parameters for the weighing process like tare weight and offsets.
Oil and Gas (MDIS)
The MDIS (MCS-DCS Interface Standardization) companion specification defines the interface between subsea control stations and distributed control systems. It’s used in offshore oil and gas operations where reliable, standardized communication is safety-critical.
Glass Production
OPC UA for Glass Production covers flat glass cutting equipment and other glass processing machinery. It focuses on condition monitoring data flowing vertically to MES systems and horizontally to connected equipment.
Analyser Devices
OPC UA for Analyser Devices provides a unified view of analytical instruments regardless of the underlying device protocol. It covers everything from simple pH sensors to complex gas chromatographs.
Woodworking Machinery
Covers machines that process wood and similar materials — chipboard, fibreboard, plywood — including when covered with laminates or edges.
Other Active Areas
New companion specifications are being developed for battery cell manufacturing, high-pressure die casting, textile machinery, surface treatment, and many more. The OPC Foundation maintains a complete list of all published and in-progress specifications.
Base Information Models: The Foundation Layer
Many companion specifications don’t build directly on the OPC UA core. Instead, they build on intermediate base models that provide common types shared across industries.
OPC UA for Devices (Part 100) defines base types for any kind of device — DeviceType, BlockType, and related structures. Many industry-specific specs inherit from these types. For example, both OPC UA for Analyser Devices and OPC UA for Machinery build directly on Part 100.
OPC UA for Machinery (Part 200) adds common definitions specific to industrial automation that are then reused across companion specifications for machine tools, robots, packaging, and more.
This layered approach prevents duplication. Common concepts are defined once and reused everywhere, making the overall ecosystem more consistent.
How to Use Companion Specifications in Practice
For device manufacturers
If you build industrial equipment, implementing a relevant companion specification makes your device instantly interoperable with any OPC UA client that supports that spec. The steps are straightforward. Download the nodeset file from the OPC Foundation. Import it into your OPC UA server (most SDKs support this directly). Map your device’s internal data to the types defined in the specification. Test with standard OPC UA clients to verify compliance.
The OPC Foundation provides guidelines and templates for creating and implementing companion specifications, available in their developer tools section.
For system integrators
When connecting equipment from multiple vendors, check if they support a common companion specification. If they do, integration becomes dramatically simpler — you configure once against the standard model, and it works for every vendor that implements it.
If a vendor hasn’t implemented the companion spec but supports OPC UA, you can often map their proprietary data model to the standard model using middleware or gateway tools.
For end users
When specifying new equipment purchases, require support for the relevant OPC UA companion specification in your procurement documents. This ensures future interoperability and protects your investment. A machine that supports OPC UA for Machine Tools will integrate with your MES regardless of which vendor you choose for the next machine.
Compatibility note
An OPC UA client that doesn’t know about a specific companion specification can still communicate with a server that implements one. The base OPC UA types are always present, so basic data access always works. The companion specification adds richer structure and semantics on top — clients that understand the companion spec get more value, but no client is locked out.
The UA Cloud Library
The OPC Foundation hosts a cloud-based library of companion specifications at uacloudlibrary.opcfoundation.org. This allows developers and engineers to browse available information models, download nodeset files, and configure cloud applications using companion specifications before even connecting to physical assets.
This is a significant development. Traditionally, you had to connect to a live OPC UA server to discover its information model. The Cloud Library lets you design your integration offline — setting up dashboards, analytics pipelines, and data mappings during the engineering phase rather than during commissioning.
Why Companion Specifications Matter for Your Business
The practical benefits come down to three things.
Faster integration. Instead of weeks of custom engineering for each vendor’s equipment, you configure once against a standard model. Adding a new machine from a different manufacturer takes hours, not days.
Vendor independence. Your MES, SCADA, and analytics investments aren’t locked to a specific equipment vendor. Any machine that implements the companion specification works with your infrastructure.
Future-proofing. As companion specifications evolve and new ones are released, the ecosystem becomes richer. Equipment you buy today, with companion spec support, becomes more valuable as more tools and platforms support the same standards.
Conclusion
OPC UA companion specifications turn a generic communication standard into a complete interoperability solution. They define the shared vocabulary that lets machines from different vendors, in different industries, describe themselves in ways that any client can understand.
With over 60 published specifications and dozens more in development, the coverage is already broad — from plastics and robotics to food processing and oil and gas. The VDMA alone coordinates roughly 40 working groups creating these standards.
For anyone building, buying, or integrating industrial equipment: companion specifications aren’t optional extras. They’re the layer that turns OPC UA connectivity into true plug-and-play interoperability. Check what’s available for your industry, require it in your specs, and build on it. The more widely they’re adopted, the more everyone benefits.