OPC Unified Architecture (OPC UA) Specification

OPC Unified Architecture (OPC UA) is the most recent set of OPC specifications. It unifies all the previous specifications into one. OPC UA provides all the capabilities of Classic OPC (mostly based on DCOM) and is even backwards compatible with Classic OPC. OPC UA also adds various capabilities that were unavailable in previous specifications. OPC UA enables programmers to select various data transportation methods from high-speed TCP/IP to standards-based HTTP Web Services. Messages can even be encoded in XML SOAP to enable them to easily pass across the Internet and non-Microsoft operating systems.

OPC UA also enables users to take advantage of various information models to transfer data as simple as a temperature reading to as complex as a work order. OPC UA also enables vendors to specify their own custom information models.

The OPC Foundation (www.opcfoundation.org) is responsible for defining and maintaining the OPC UA specification. The existing OPC COM based specifications have served the OPC Community well over the past 10 years, but as technology moves on so must the interoperability standards. Here are the factors that influenced the decision to create a new architecture:

• End-users want a single OPC server to house all their real-time and historical data
• End-users want to implement OPC on non-Microsoft systems, including embedded devices
• End-users are deploying OPC over the Internet, so Web Services and SOA (Service Oriented Architecture) are an appropriate alternative to DCOM
• Other collaborating organizations need a reliable, efficient way to move higher level structured data

The Unified Architecture (OPC-UA) is described in a layered set of specifications broken into Parts. It is purposely described in abstract terms and in later parts married to existing technology on which software can be built. This layering is on purpose and helps isolate changes in OPC-UA from changes in the technology used to implement it. The structure and depth of material to absorb in learning OPC-UA is harder than the OPC COM Specifications.

The OPC Training Institute's Level 3 course, called OPC Unified Architecture, takes end-users and integrators on through the OPC UA specifications and applications. Attendees will learn OPC UA and how to properly apply the technology in their plants.