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OPC UA adds RESTful API for IT application access

May 2, 2023

The OPC Foundation reported Apr. 17 that it’s expanding the OPC UA networking standard with a representational state transfer (RESTful) application program interface (API) to allow worldwide access to data made available by implementations of more than 90 standardized information models by IT applications.

This extension was requested by IT companies to ensure efficient and standardized access to important information. IT applications need to use data from OT in data spaces, digital twins and the metaverse. These solutions often share information between multiple companies. In many cases, they exchange information via proprietary hypertext transfer protocol (HTTP) REST APIs.

OPC UA is already equipped with many building blocks, such as session-less services and security features. Those building blocks already cover many aspects required to provide standardized information via RESTful interfaces. With the addition of HTTP REST, applications outside of the OPC UA ecosystem can now access this information. OPC UA also includes the transfer of meta-information, such as server timestamp, source timestamp, value, and quality of the individual information. Direct access via OPC UA allows these pieces of information to be shared with the cloud and used in applications like the digital twin.

The expansion of OPC UA with REST is less likely to be adopted at the field level, but in gateways and cloud services. Cloud companies can now access standardized information and use it efficiently to optimize the business processes of their customers and unlock new use cases.

"This extension of OPC UA with a standardized mapping to a RESTful interface is a step forward in ensuring the interoperability of industrial automation and IoT systems," says Stefan Hoppe, president and executive director of the OPC Foundation. "By enabling access to information provided by implementations of more than 90 OPC UA domain-specific information models through standardized RESTful APIs, we’re making it easier for developers to create OPC UA-enabled applications that can communicate with other web-based systems and applications such as digital twins and the metaverse."

Erich Barnstedt, chief architect for standards, consortia and IIoT, Azure Edge and Platform at Microsoft Corp., adds, “When volunteering to chair this working group to cover the requirements of our projects, I didn’t expect such a big industry interest from others. With more than 50 companies participating, I’m sure the resulting extensions will be of great value for the entire industry.”

The REST group, as a sub-group of the OPC Foundation UA Working Group, the REST group will discuss use cases for OPC UA in edge and cloud-computing environments using the proposed HTTP REST interface. Non-exclusive examples for work items are:

  • Generic REST interface definition for common OPC UA services (read, write, call, etc);
  • Standardized mapping of OPC UA service parameters to datatypes commonly used in RESTful APIs;
  • How the existing session-less OPC UA service can be used with a REST interface;
  • Define a concept to provide REST interfaces for companion specification use cases;
  • Define requirements for security;
  • Building prototypes and a demonstration; and
  • Define an OpenAPI-compatible REST interface using Swagger.

For more information or to join the REST group, contact Karola Wauro at the OPC Foundation at [email protected].

About the Author

Jim Montague | Executive Editor

Jim Montague is executive editor of Control.