OPC UA: The One and Only

April 27, 2009
OPC UA Is the Solid Foundation, Vision and Infrastructure of the OPC Foundation
By Eric Murphy, columnist

The release of the OPC UA Phase One deliverables marked a major milestone for OPC UA adoption. Despite any quiet murmurings to the contrary, OPC Unified Architecture is the one and only specification the OPC Foundation is backing as the future of industrial connectivity. The OPC Foundation Board of Directors and the vendor representatives of the Technical Advisory Committee (TAC) have recently approved creation of the OPC UA Accelerated Adoption Working Group. This group's purpose is to refine the current OPC UA documentation and code deliverables to streamline the effort required to achieve the equivalent functionality of the classic OPC specifications in OPC UA implementations. So, what is the story behind the formation of this working group?

OPC UA Brought to Task 

Every OPC deliverable is produced from working groups made up of volunteer representatives of automation vendors, developers and industry experts. Anyone who has participated in a committee knows that not every decision is unanimous, and everyone will have different opinions on the best way to meet the needs of the greater user community. As the scope of OPC UA was introduced to the OPC community, criticisms arose from inside and outside the OPC Foundation on the complicated perception OPC UA presented. OPC UA provides a rich set of communications, reliability mechanisms and a highly configurable information modeling architecture. It is intended to provide high-speed, reliable discovery and communication for any vendor or consortium's information model architecture. Some people felt the scope of OPC UA was presenting the perception of a complicated solution and believed some users would be hesitant to fully adopt OPC UA into their products. In order to address these concerns the OPC Foundation Board of Directors commissioned a task force, codenamed OPC.NET, to investigate the feasibility of producing a streamlined approach to migrate existing classic OPC installations to the OPC UA.

Enter the Task Force

A small subset of OPC Foundation members was commissioned as a task force to perform the feasibility study. Part of the reasoning behind the original codename of OPC.NET was the belief that providing a Microsoft-specific set of interfaces based on the Windows Communication Foundation (WCF) would be a good fit with existing classic OPC installations. The main focus was to address the fundamental reliability problems associated with DCOM, and provide enhancements to allow classic OPC-based servers to be easily migrated without understanding the intricate details and underlying communications of OPC UA. As the group's scope became more defined, other codenames such as OPC UA Express and Express Interface (Xi) were used to better describe the group's goals. After about a year's work-in-progress of developing a draft specification and sample code, the group looked to other OPC vendors to validate the feasibility of proposed approach. This initial outreaching resulted in whispers of a "new" OPC specification being developed and consequently sent ripples of concern among members of the OPC community.

Give Do Process its Due

The normal process associated with any OPC feasibility type activity is to evaluate and assess both market and technical value proposition opportunities. If the opportunity merits a formal working group, then the TAC forms a working group, and the OPC-F works the process of competitors working together to develop the feasibility into a final product, inclusive of specifications, technology and a well-defined certification process. After a formal review by the Technical Advisory Council and the OPC Foundation Board of Directors, a decision was made to take the work of the feasibility task force forward by commissioning the OPC UA Accelerated Adoption Working Group. The excellent initial work by the task force provided a solid basis for the new working group charter and action items, geared toward advancing the widely acclaimed OPC Unified Architecture specifications.

Moving from Feasibility to Refinement

OPC UA has been an ongoing development by many committed OPC Foundation members for almost five years. At initial glance, the scope of OPC UA is complicated. However a more detailed view shows OPC UA has a highly scalable architecture. The concept known as Profiles allows specific vendors to develop and support the OPC UA components best suited for their specific application environment. Also, OPC UA is truly platform-independent. It is not dependent on any operating system-specific technology, but at the same time it leverages the opportunity for specific operating systems to facilitate easy adoption and deployment into real products. The main conclusion of the OPC Foundation reviews of the task force's work was that the new working group should heavily leverage the fundamental advantages of OPC UA when formally defining the charter for the new working group.

OPC UA Accelerated Adoption is Born

OPC is in the business of developing specifications through collaboration and having competitors develop best-of-breed technology. OPC technology is all about multi-platform, secure, reliable interoperability, while at the same time not being a lowest-common-denominator approach. For any OPC specification, success is measured by the level of adoption of the technology. With these precepts in mind, the charter for the Accelerated Adoption Working Group was defined as to develop further refinements to the existing OPC UA specifications, documentation and code deliverables in order to reduce the development effort to implement the equivalent functionality of the OPC DA, HDA, and A&E COM Specifications. In a later phase, the working group may consider additional accelerated adoption refinements in feature areas beyond those of the classic OPC Specifications, such as Type Model, Methods, Historical Event Access and other OPC UA features.

Main deliverables of this new working group include using newly defined Profiles and providing OPC UA Jump Start Kits (JSKs) for migrating existing classic OPC implementations to OPC UA. The Profile JSKs are to include a focused set of documents, implementation guidance, sample code, SDK and verification tools tailored for facilitating the migration of specific classic OPC capability. Reading the full set of OPC UA Specifications will no longer be necessary to provide an OPC UA implementation of an existing classic OPC service.

OPC UA: The One and Only

While these target deliverables will be designed to accelerate OPC product adoption, it is important to realize that complete interoperability with the currently released OPC UA Release 1 deliverables is paramount. As the working group name suggests, the work of the initial task force is geared toward accelerating the adoption of the proven OPC UA technology. OPC UA truly is the one and only. Tom Burke, President of the OPC Foundation sums it up best when he says, "OPC UA is the solid foundation, vision and infrastructure of the OPC Foundation. The mission of OPC is to provide multiplatform, multivendor, secure, reliable interoperability for many domains, including process control, factory automation, building automation, security, home and building control, and the whole energy portfolio. The OPC Foundation is always looking for opportunities for partnership and collaboration with both vendors and consortiums in the interest of providing the best-of-breed specifications and technology, solving problems that the end users want solved and that vendors are clearly motivated to adopt into real products and solutions."

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 is a member of the OPC Foundation Technical Advisory Council (TAC).  Eric is also a co-editor for the OPC Unified Architecture (UA) specifications as well as the chair of the OPC Historical Data Access (HDA) 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.