In the field of digital transformation for smart factories, the terms IoT and OPC Unified Architecture (OPC UA) have become indispensable. OPC UA enables the interoperability of a wide range of devices, machines, sensors and applications, regardless of vendors and technologies. However, many devices do not support the OPC UA standard, but rather Web of Things (WoT) from the W3C.
For the integration of W3C WoT-capable devices in OPC UA, a working group in the OPC Foundation will deal with the topic from June 27, 2023. This group has set itself the goal of creating a companion specification for OPC UA that will enable integration.
What is OPC UA?
The OPC Unified Architecture (OPC UA) is a standard for secure and platform-independent communication in the context of the Internet of Things. Thereby, a large focus is placed on Industry 4.0 and automation systems. The use of open standards and manufacturer-specific information models enables platform independence and interoperability between different devices and systems from different manufacturers.
What is Web of Things?
While OPC UA is specifically designed for Industrial IoT, WoT has an industry-independent design. This standard is designed to simplify development and implementation of IoT projects and make them more accessible. It is driven by the W3C and builds on web technologies such as HTTP, JSON and WebSockets.
Central features are:
- Simplicity: Use of familiar web technologies
- Interactivity: An abstract representation of things ensures simple interaction.
- Universal use: WoT is to support various established platforms such as OPC UA or the Open Connectivity Foundation with so-called protocol bindings.
The goal of WoT is therefore not simply to bring another standard onto the market. Rather, a defragmentation is to be carried out by reusing established web technologies and creating support for various IoT platforms with their respective protocols.
This involves working with a so-called Thing Description (TD). A Thing is the abstraction of a physical or virtual entity that can be interacted with. A TD describes metadata and interfaces for a Thing and is provided either directly by the device or via other means by the manufacturer. It is also possible to retrofit a WoT-enabled device and create a Thing Description for it, for example to make a new acquisition obsolete.
If you would like to know more about retrofitting and new acquisition, we recommend our article Retrofitting as a solution approach for problems in the implementation of Industry 4.0.
Initiative of the OPC Foundation
As already mentioned, WoT is able to interact with OPC UA endpoints. Unfortunately, it is not always the case that WoT is already established and an OPC UA server should be included. Instead, the reverse case may occur, where an OPC UA server exists that is to be enabled to communicate with non-OPC UA-capable devices that are, however, WoT-capable.
The OPC Foundation has set itself the task of solving this problem. Work has already been started on the UA-EdgeTranslator. This is to translate proprietary protocols that support WoT TDs to OPC UA. This will not only make it possible to read and write data with the OPC UA Server. It should also be possible for the first time to configure assets using the TDs. It is worth mentioning here that the configuration is supplementary and is only intended to configure WoT-enabled devices that would otherwise have to be configured via a direct HTTP interface.
Building on this initiated project, the aforementioned working group has set itself the goal of formulating and implementing a companion specification.
The OPC UA standard has an important role in Industrie 4.0 but is not supported by all devices. For this, Web of Things is a promising addition to cover an even larger set of devices with an existing IoT application built on OPC UA. The work of the OPC Foundation should soon also make it possible to integrate WoT-enabled devices into an existing OPC UA server and communicate with them without much additional effort.