OPC UA and Bridging the Chasm
Anyone who is working with new or innovative technology, and wants the world to adopt it as their standard, is aware of the all important need to cross the chasm between early adopters and mainstream markets. As OPC UA begins its approach to the chasm, the infrastructure is already being laid to ensure it can successfully bridge the gap.
Im referring of course to Geoffrey Moores book Crossing the Chasm , which explores the revised Technology Adoption curve, comprised of five main segments; innovators, early adopters, early majority, late majority and the laggards. Figure 1 below depicts the chasm that exists between the early adopters of the idea (the technology enthusiasts and visionaries) and the early majority (the pragmatists).
Crossing the chasm between visionaries and pragmatists.
The two groups have very different expectations. OPC has successfully crossed the chasm, and is well up the slope of the Early Majority, where as OPC UA is just being released, it is clearly left of the gap among the Visionaries.
OPC and the Pragmatists
OPC provides a functional interface for reading and writing data in an efficient and deterministic way. There are separate specifications to address different data semantics, including real-time data, historical data, alarm and event information and batch data. The OPC specifications are implemented on the Microsoft COM/DCOM protocol which offered several advantages, including high speed data transfer capability, efficient handling of multiple client/server connections and built-in operating system level security. Many of the major control systems, machine interfaces, historians, expert systems and other automation applications are widely deployed on Microsoft platforms. In addition, the interfaces are comprehensive enough to provide the functionality that users require, yet simple and practical to implement, which results in wide vendor acceptance. These factors all aided OPC in gaining enough momentum to cross into the pragmatist domain.
OPC UA and the Visionaries
The primary purpose of OPC was to solve the integration problem between devices and PC based client applications. Industrys desire for connectivity standardization has led to OPC being used in a wider range of applications than was originally considered. The scope now extends to enterprise level interoperability, which includes applications from the field level all the way to realm of enterprise spanning software. OPC UA was introduced to meet the changing technology and market requirements. The OPC UA architecture encompasses and unifies the functional data formats addressed by the COM based OPC specifications. The OPC UA specifications also go farther in setting standards for application security, reliability, audit tracking and information management. Another key difference of the OPC UA specifications is that they are implemented on a service base architecture, which leverages existing standards such as XML, SOAP and the WS initiatives. In order for this newer technology to gain adoption with the conservative organizations on the right of the chasm, it must submit proof that the technology works in practice. The OPC Foundation is supplying the infrastructure for that proof in several ways.
Bridging the Gap
OPC UA has an advantage over other technologies facing the chasm, in that OPC is already firmly established on the other side. The OPC Foundations migration plan is more analogous to constructing a bridge, than jumping the divide. Just like building a suspension bridge, the implementation will be done in stages. The stages can be thought of as; installing the cable anchors, constructing the towers, spinning the cables, and finally construct the decking and finishing features. Since my background is in Chemical engineering, the Civil Engineers will have to forgive my simplification of the process.
Stage 1: Installing the Cable Anchors. The anchors provide the foundation and main support for the structure. OPC UA is based on the firm foundation provided by the OPC specifications, as well as other existing service based standards. The Data Access, Historical Data Access and Alarms and Events OPC specifications have countless installations, with years of time tested performance. The OPC UA specification Parts 8, 9 and 11 respectively map onto these proven and familiar foundations. In addition, the OPC UA specifications are built on Service Orientated Architecture technologies that themselves are successfully crossing or have already moved into the mainstream domain.
Stage 2: Constructing the Towers. The towers are the framework of the bridge which carry the load and therefore are key components of the infrastructure. Since OPC UA is anchored by existing OPC installations and products, the ability to easily leverage and extent the current user base is a fundamental aspect of adoption. To that end, the OPC Foundation will also be releasing industrial-grade Wrappers and Proxies that will seamlessly add OPC UA functionality to existing OPC clients and servers. Software components will be available for OPC DA, HDA, A&E and XML-DA products that will provide additional OPC UA features such as improved security, reliability, transport and session management.
Stage 3: Spinning the Cables. The technique of cable spinning allows for a cable of any length and thickness to be formed by binding together thin wires. To achieve mainstream adoption, implementers will need to easily add functionality to the base structures to create powerful OPC UA products. In addition to the Wrapper and Proxies software, the OPC Foundation will also be providing the OPC members with the source code, supporting documentation and reference designs used to create the OPC UA components. This will significantly improve the time to market, and quality of additional OPC UA products, that offer richer information models, complex data handling and industry specific applications
Stage 4: Deck Construction. The deck system is comprised of girders, beams, stringers and concrete. This is the final stage of creating the solid, trusted link between both sides of the divide, in preparation for the public masses. In terms of OPC UA, this represents the supporting activities that the OPC Foundation is spearheading to ensure that OPC UA is accepted and used by a wide audience. These activities include the development of a comprehensive Testing and Certification process for OPC products. Pragmatists require proof that a technology is compliant, interoperable and maintainable. There is a separate OPC Compliance group that is working on defining OPC UA test procedures, comprehensive compliance testing tools, interoperability testing sessions as well as an independent Test Lab. In addition, the OPC Foundation is working closely with major standards bodies, such as ISA, IEC, MIMOSA, EDDL, FDT and others. Collaboration with these standards will help to better facilitate adoption and acceptance of the OPC UA specification.
OPC UA represents a significant step towards transforming data into information for the enterprise, but that does not mean adopters should have to take a leap of faith to achieve this. The majority of OPC users today are comprised of individuals who choose solutions that are standardized, practical and secure. Therefore every effort is being made to ensure there is a clear, effective and seamless migration path to OPC UA, and build the infrastructure for the interoperable data link from the shop floor to the top floor.
- Moore, Geoffrey A., Crossing the Chasm: Marketing and Selling High-Tech Products to Mainstream Customers, HarperCollins Publishers, New York, N.Y., 1991.
|About the Author|
Eric Murphy, BSc, PEng (Alberta), is a chemical engineer with a process control specialization and an OPC expert. Eric has been a part of the OPC community since its early beginnings in the mid-1990s. He is heavily involved with the OPC Foundation and currently acts as the chair for the OPC Historical Data Access (HDA) working group. Eric is also a member of the OPC Technical Steering Committee (TSC) and an active member of the OPC Unified Architecture (UA) working group. Visit Eric at his Blog the OPC Exchange to follow the latest trends and discussions about OPC technology, or click here for free downloads.