Onboard the 'Unified Architecture' train

Frank O. Smith -- Control Engineering, 8/1/2006

The OPC Foundation and four of its member companies officially announced the new Unified Architecture (OPC-UA) for data and information sharing between the plant floor and the enterprise at the ARC Advisory Group's annual forum in Boston in June. OPC-UA unifies all existing OPC specifications and leverages service-oriented architecture (SOA) based Web services technology as the communication mechanism with enterprise systems.

Interoperability is 'not about data anymore, but information—taking information from the shop floor to the top floor,' said Tom Burke, president and executive director of OPC, during the press briefing. 'We started by looking at all the protocols in our domain. The number is huge. We have thousands of applications and devices and protocols out there—and how do we make it all work together? The [OPC-UA] concept is about supporting all that and making OPC real.

'OPC-UA is very new,' he added.

The OPC Foundation, however, is not new. It was created 10 years ago by a consortium of automation vendors and interested parties to improve connectivity and interoperability through open standards. OPC—which originally stood for OLE (object linking and embedding) for process control, which was its goal—was historically based on Microsoft's OLE common object model/distributed common object model (COM/DCOM) technologies. OPC-UA is an evolutionary step forward based on Microsoft .Net technology and exploits the power of XML as the communications mechanism for invoking services between the automation and enterprise layers. OPC-UA provides complete data access and exchange services for such functions as configuration, diagnostics, and runtime operational data, enabling greater asset utilization and performance that impacts the bottom line.

'ARC is a strong advocate for anything that is based on open standards and makes interoperability easier, that can provide connectivity between the plant floor and the enterprise, but does it in a scalable way,' said Craig Resnick, ARC research director. 'OPC-UA provides for what is new in the plant, but also for what the whole legacy entails.'

Burke said that, in the early days, 'the paradigm was very narrow. DCOM was the great technology that OPC was based on, for all data within the corporate firewall. Now we have to move information across the corporate firewall.

'We took all the OPC functionality that was mapped in COM and DCOM and made it into services for things like queries, reading and writing, and subscribing. We came up with a common information model to implement it as a base set of services. Then we took the step of collaboration with ISA, IEC, OAGI, and EDDL, who are data modelers. They define what the data are, and OPC-UA becomes the transport mechanism.'

But the initiative doesn't stop there. 'It's not good enough to come up with an architecture and have vendors build to support it,' Burke said. 'You have to ensure that the products work.' The OPC Foundation has extended its vendor self-test certification program to include third-party certification for validating specification adherence. Those that pass third-party certification will be able to carry a new OPC-UA certification logo on their products, further ensuring interoperability of their products within the new Unified Architecture.

'We've all fundamentally agreed this is what the end users wanted. Now we've reached a point where it is a reality,' Burke added.

Burke was joined at the podium by representatives from Softing, Kepware, SAP, and Microsoft. Other vendors used the occasion of the forum to make announcements of OPC-UA ready products or to endorse the new standard (see box above).

Frank O. Smith is contributing editor, Control Engineering, www.controleng.com

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