By Stefan Hoppe, Global Vice President, OPC Foundation A central challenge posed by Industrie 4.0 and the Industrial Internet of Things (IIoT) is the secure, standardized exchange of data and information between devices, machines and services across different industries. As early as April 2015, the Reference Architecture Model for Industrie 4.0 (RAMI 4.0) recommended only IEC standard 62541 OPC Unified Architecture (OPC UA) for implementing the communication layer. In November 2016, the Industrie 4.0 Platform published a checklist for classifying and advertising products as Industrie 4.0 “Basic,” “Ready,” or “Full”. To comply with the “Industrie 4.0 communication” criterion, even the lowest category requires the product to be addressable over the network via TCP/UDP or IP and to integrate at least the OPC UA information model. As a result, any product being advertised as “Industrie 4.0-enabled” must be OPC UA-capable (either integrated or via a gateway). The checklist also stresses the information modeling property of OPC UA.
OPC UA is not just protocol – it’s a whole lot moreWhen it comes to information modeling, many small and medium-sized companies tune out, because they compare OPC UA with other protocols like MQTT and assume that it has limitations. We often hear questions like, “OPC UA can’t communicate directly with the cloud, can it?” First of all, every equipment and machine manufacturer already provides an implicit information model with data interfaces (via various protocols). Humans have learned to adapt to the computer’s way of ‘thinking’ – documenting what the bits, bytes, and hex codes mean. This new world full of devices capable of a service-oriented architecture (SoA) helps humans understand the “things” more quickly and easily, because they offer “services” and describe their underlying meaning. The subject of SoA is nothing new in the world of IT. Now, however, it extends all the way to the “things” themselves. This is where OPC UA comes to play, providing the framework for industrial interoperability. Machine and device manufacturers describe the object-oriented information of their systems and define the access rights along with integrated security features. Germany’s BSI (Bundesamt für Sicherheit in der Informationstechnik, or Federal Office for Information Security) published the results of its security analysis of OPC UA in April 2016 in highly positive terms. This was because machine builders keep full control of the data, i.e. they can distribute it in a targeted and controlled manner, which enables them to participate monetarily in big data applications and data analytics. To exchange the data, OPC UA combines two mechanisms to implement various scenarios:
- A client-server model, in which OPC UA clients use the dedicated services of the OPC UA server. This peer-to-peer approach provides a secure and confirmed exchange of information, but with limitations regarding the number of connections.
- A publisher-subscriber model where an OPC UA server makes configurable subsets of information available to any number of subscribers. This kind of broadcasting mechanism provides an unconfirmed “fire and forget”-style exchange of information.