Mr. Emde, the Pub/Sub extension for OPC UA is not yet available as a release, but OSADL is already presenting an open source implementation. Why the rush?
Emde: When we received the first reports about two years ago that a new standard protocol for industrial real-time communication was being developed, we were very keen to find out whether an old dream was now coming true. At that time, however, our members had little interest in becoming active in this direction. But then came SPS IPC Drives 2017: almost every visitor asked for an open source implementation of OPC UA Pub/Sub in the second sentence! It was immediately clear to us that we had to get such a project off the ground!

Why did the development happen so quickly and who is behind the project?
Emde: Four fortunate circumstances came together. Firstly, an implementation of OPC UA without Pub/Sub already exists - it is based on the IEC 62541 standard and is available under an open source license. Secondly, the Fraunhofer development team, which was already involved in the OPC UA implementation according to IEC 62541, offered to implement the pub/sub extensions and integrate them into the main developer branch of the open62541 project. Thirdly, Kalycito Infotech, an Indian system integrator familiar with open source software, had experience in connecting OPC UA to TSN hardware and was looking for partners for such a project. And fourthly, OSADL members Heidelberger Druckmaschinen, Kontron, Linutronix, Pilz, Sick and TQ-Systems were interested in the technology and willing to provide some of the necessary funding.

With such a good starting position, the decision of the three players - Fraunhofer IOSB, Kalycito and OSADL - was quickly made: We set up an OSADL working group and implemented initial goals. These include the implementation of a minimum required set of pub/sub functions by the Fraunhofer team, their integration into a demonstrator for embedded world 2018 by Kalycito and the establishment of a suitable test environment in the QA farm by OSADL.

What does the demonstrator show and how market-ready is the development already?
Emde: The demonstrator shows several TSN-capable embedded systems that transmit both real-time and non-real-time data. Using various measurement methods, we show that the current OPC UA pub/sub implementation via TSN makes it possible to transmit real-time data to multiple recipients without a broker and without the determinism of non-real-time data being affected. The software developed in our project is already running stably on various platforms; however, we still need practical experience and feedback from the community before it is ready for series production.

What happens after the release in March?
Emde: It depends on how the community reacts! Will we be able to get other developers excited about the new code and attract more partners? If this is the case, we want to continue developing the new and old modules and gradually implement the missing features, the priority of which will be decided by the users.

Do these developments take place in cooperation or rather in competition with the OPC Foundation?
Emde: The OPC Foundation and our project complement each other perfectly: the OPC Foundation takes care of standardization and thus makes a decisive and indispensable contribution that we could never provide. Our project helps to create suitable framework conditions so that OPC UA Pub/Sub can be implemented in an open source community supported by the industry and used worldwide without restriction - an ideal prerequisite for the further acceptance and dissemination of OPC UA Pub/Sub, which in turn is certainly in the interests of the OPC Foundation.