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OPC UA Adds Standardized REST Interface

May 9, 2023

The OPC Foundation says this addition is a significant step forward in ensuring the interoperability of industrial automation and IoT systems by allowing IT applications to access to OPC UA data.

The OPC UA standard has been expanded by the OPC Foundation to add a RESTful interface that allows remote access to information in more than 90 standardized IT application models.

The OPC Foundation says this extension was requested by IT companies that “need the ability to utilize data from operations technology for use in concepts such as data spaces, digital twins and metaverse applications.”

With the addition of HTTP REST, applications outside the OPC UA ecosystem can now access OPC UA information. The OPC Foundation notes that the OPC UA specification includes “the transfer of meta-information such as server timestamp, source timestamp, value and quality of the individual information. 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.”

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

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

Generic REST interface definition for common OPC UA services (e.g., read, write, call).
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.

What is REST?

REST is a set of architectural constraints, not a protocol or a standard, according to RedHat, a supplier of cloud infrastructure, middleware, cloud-native application development, and management and automation solutions.

Developers can implement REST in a variety of ways, RedHat says, such as: when a client request is made via a RESTful API (application programming interface), it transfers a representation of the state of the resource to the requester or endpoint. This information, or representation, is delivered in one of several formats via HTTP, such as JSON (Javascript Object Notation), HTML, XLT, Python, PHP, or plain text.