OPC-UA poised to integrate us all
By Roy Kok
The OPC Foundation, working with key industry vendors since January 2004, has defined the next generation of OPC—OPC-UA.
It is a significant upgrade of the technology invented back in 1996. With OPC-UA specifications now released, and early adopter products already on the market, OPC-UA is poised for mass adoption by the automation industry.
The first generation of OPC evolved over time, addressing the most critical issues first such as data access, followed in time by more complex data types and data interactions. This resulted in the industry haphazardly adopting many specifications.
OPC-DA (Data Access) is the most widely adopted specification, followed by OPC-A&E (Alarms and Events) and OPC-HDA (Historical Data Access). The UA is for Unified Architecture – the integration of earlier OPC specifications into one, all encompassing technology, able to handle the diverse data types of Data Access, Alarms and Events, and Historical Data Access.
OPC-UA defines how servers will highlight their capabilities, through compliance profiles, enabling client applications to understand and support server capabilities automatically.
While the first generation of OPC addressed the most pressing issue, that of software application interoperability on Microsoft platforms, time has proven the problem of interoperability is a much broader issue. OPC-UA is a communication standard, no longer limited to Microsoft platforms.
OPC-UA leverages the next generation of communications—Service Oriented Architecture, IP communications, and Web Services and is divorced of Microsoft-only technologies letting OPC-UA become a broadly applied standard, on operating system platforms from the deeply embedded, VxWorks, to Microsoft platforms and enterprise platforms like Linux.
OPC-UA Profiles also assist in scalability, to address communications from a device all the way up to interactions between MES, ERP, Historian, etc. solutions. A reliance on industry standards such as Web Services also delivers firewall friendliness and easy-to-manage access for the IT professional.
With a broader range of platforms comes the need for security that spans them all, and security that can address the unique rules, roles, and individual requirements of every installation. OPC-UA leverages industry standards delivering a very powerful, secure by default, certificate-based security.
Certificates follow the x509 standard, and their use delivers security flexibility based on users, applications, locations, and access permissions such as read/only or read/write. Process engineers will have a great deal of control over who can access what and why.
Data with context
Data is NOT information. Data is simply data. The first generation of OPC provided access to data and provided additional information of time and quality. While representing an excellent first step in interoperability, modern systems can benefit greatly from data, delivered with a much greater level of context. It is context that turns data into information.
Context can take many forms, as simple as an array of data associated with a machine or collected at a common moment of time. Context is commonly represented by Data Models, definitions of data, data attributes, and their structure. OPC-UA delivers the ability to support complex data objects, no longer requiring access to data one variable at a time. The architecture of OPC-UA enables it to support both existing data models, industry standards such as ISA95, ODVA, ISA88, or automation vendor specific models. Thus, OPC-UA is the pipe able to handle the future needs of intelligent data handling.
There are no competing technologies for automation interoperability. The OPC Foundation, as a standards body and through the support of all its members, is the only provider of technology for interoperability across all levels of the product in the automation marketplace. OPC-UA has proven flexible enough that it is attracting interest in new areas, outside the traditional market of automation such as Smart Grid, Home Automation, and Windows for Cars and applications in the medical device space, complex analyzer space, and the building control industries.
As for timing and rate of adoption, 2009 represents the year products will come to market. A handful of products are available and selling today. Many more are in design. Ideally, you will never need to know about OPC-UA specifics. The products you use today will simply arrive, as an update, or new version, with new features and benefits derived through the use of OPC-UA.
ABOUT THE AUTHOR
Roy Kok has an electrical engineering degree and over 30 years of automation industry experience. He is vice president at Kepware Communications, a company that provides communications software for automation, systems integration, and is an early adopter of OPC technology.
OLE for Process Control (OPC) is an interface specification. Applications, which implement the OPC interface, are able to interoperate without the developer needing to control both the server and client development. By following the OPC interface, clients and servers from different manufacturers can communicate and interact successfully. The OPC interface offers the types of interactions that are typical of process I/O hardware such as PLCs, DCSs, and direct I/O boards.
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