OPC Unified Architecture






UA References

UA Whitepapers and Articles


Background to UA

OPC Unified Architecture (UA) is the new generation of OPC. The first parts of the specification were released August 2006, with a full phase I release in February 2009.

OPC Foundation has developed UA in recognition of the following factors:

  • Microsoft's COM and DCOM, the foundations of earlier OPC specifications, are now officially legacy technologies.
  • Web services now offer the primary mechanism for data transport between computers (and also provide a better option for communications with plant-floor devices).
  • Earlier OPC specifications failed to provide a single coherent data model - e.g. the Data Access item hierarchy was totally disjoint from that offered by Alarms & Events.
  • Backwards compatibility with earlier OPC specifications is key to acceptance of any new standard.
OPC UA motivation

The UA initiative offers a single coherent data model, and uses web services for primary transport. A .NET (WCF) API will also be offered for developer convenience and DCOM-like performance.

More on OPC UA

OPC UA is based on few main principles that highlight key benefits for users... MatrikonOPC, key member in the OPC foundation, touches briefly on those principles and benefits. Read more here!


OPC Foundation has recognised that cooperation with other standards bodies is critical to acceptance throughout the enterprise. Initial UA specification sections will address the core areas of DA, AE and HDA. In parallel, OPC Foundation is working with bodies such as MIMOSA, ISA and OMAC to extend the UA standard to Batch, Asset Management and other areas.

UA to Date

Key milestones in the history of OPC UA:

Architecture vision.
UA Committee formed.
Implementation sub-committee formed.
First prototype specifications.
First Release Candidate specifications.
UA demonstration at ISA Expo 2005, Chicago, IL.
Full set of draft specifications published.
OPC Foundation launches dedicated Unified Architecture page.
"Final" Release Candidate specifications published.
First OPC UA Specification parts (1-5) reach Release status.
OPC UA Specification part 8 (Data Access) released.
Unified Architecture DevCon held in Munich, Germany.
Beta versions of Schema and WSDL documents for UA published.
OPC UA Specification part 11 (Historical Access) released.
OPC UA SDK for .NET available at beta level.
OPC UA Specification part 10 (Programs) released.
Unified Architecture DevCon held in Scottsdale, AZ. PowerPoints and screen capture videos for more than 20 of the DevCon presentations are available to Foundation members and non-members alike.
It's announced that OPC UA is to become an IEC international standard: IEC 62541-x.
Automation security specialist Digital Bond posted information on vulnerabilities in the UA specification and SDK. OPC Foundation undertook to address these prior to full release.
Unified Architecture DevCon and Workshop held in Munich, Germany.
OPC Foundation's Analytical Device Integration (ADI) Working Group announced the availability of a completed review draft of the OPC UA Analyzer Devices Specification.
Full phase I release of the UA Specification - this includes parts 1 to 8, with the official specification version being 1.01. Simultaneously, the UA SDK reached Release Candidate status, with final release awaiting only approval of the License and Distribution Agreement by the Technical Advisory Council.
First full release of the OPC Foundation UA SDK for C/C++ and .NET.
OPC UA Specification part 9 (Alarms and Conditions) released.

The Outlook for UA

Phase 1 is UA, as desribed above, is just the first step. OPC Foundation is setting up a Working Group to take UA through it's next phase.


The OPC Foundation page on UA includes plans for timescales and deliverables.


OPC Foundation has published Release or Draft versions of the first 11 (of 12) initial parts of the UA specification. These downloads are available only to Foundation members.

Core specification parts "define the structure of the OPC address space and the services that operate on it":

  • Part 1: Concepts - released
  • Part 2: Security - released
  • Part 3: Address Space - released
  • Part 4: Services - released
  • Part 5: Information Model - released
  • Part 6: Mappings - released
  • Part 7: Profiles - released

Four "Access Type" parts build on the core framework defined by parts 2 through 7:

  • Part 8: Data Access - released
  • Part 9: Alarms and Conditions - released
  • Part 10: Programs - released
  • Part 11: Historical Access - released

Further parts have been added more recently:

  • Part 12: Discovery
  • Part 13: Aggregates


OPC Unified Architecture (OPC UA) Workshop


See our UA SDKs/Toolkits and Free Stuff pages for UA downloads from OPC Foundation and vendors.

MatrikonOPC developed a UA Wrapper, built with the latest SDK, to allow users to connect to COM/DCOM based “OPC Classic” servers using the new OPC UA specification. UA Wrapper for COM OPC Servers

UA References

OPC UA Webinars

new OPC Foundation began this series of excellent webinars for developers in April 2010.

OPC UA DevCon - June 2007

The 2007 UA DevCon was held over 3 days during June in Scottsdale, AZ. OPC Foundation has released PowerPoints and screen capture videos for more than 20 of the DevCon presentations. These are available to Foundation members and non-members alike.

ISA 2005 Presentation - October 2005

OPC Foundation has published an excellent introduction to the Unified Architecture - a presentation given at ISA 2005 by Foundation Technical Director Jim Luth.

The ISA 2005 OPC UA presentation is available from the downloads area of the Foundation site (Acrobat PDF or PowerPoint 2003 format).

The presentation shows that legacy COM-based OPC software may be accommodated through the use of Foundation-provided "UA Client Proxy" and/or "UA Server Wrapper" components. The UA Client Proxy allows existing clients to connect to UA servers, while the UA Server Wrapper allows UA clients to work with COM servers. Using the Proxy and the Wrapper together replaces DCOM with the new UA transport.

OPC UA DevCon - April 2005

OPC Foundation and Microsoft jointly hosted the OPC Unified Architecture Developer Conference 2005 in Redmond, April 19th and 20th.

UA DevCon 2005 was attended by more than 130 people, and presentations given at the conference are now available to download.

The keynote, given by OPC Foundation president Tom Burke is available to everyone. The other presentations may be accessed only by OPC Foundation members.

Original UA Press Release

OPC Foundation's original UA press release (Acrobat PDF format) from October 2003 remains available.

UA Whitepapers and Articles


White paper: "OPC UA: 5 Things Everyone Needs To Know Whitepaper" - This whitepaper talks about: What is OPC UA, how does it help you, and where can I get it? These questions are best summed up in the five things everyone needs to know about OPC UA.

White paper: "OPC UA Security: Do You Have Reservations? " - This whitepaper discusses some of the concepts of OPC UA Security.

White paper: "Implementation of the OPC UA Information Model for Analyzers" - discusses selected aspects of the OPC Unified Architecture information model. The white paper is intended for process architects and software developers to help deployment of OPC UA-ready solutions in real production environments. The general scope of the discussion makes the paper a case study that can be useful for the deployment of any OPC UA product.

White paper: "The OPC UA Security Model for Administrators" - discusses how to use the OPC UA security model to ensure application and transport security. The target audience for this document are systems administrators and end users. A second whitepaper will discuss the security model from the perspective of a software developer.

Other Articles

A Roadmap to UA Downloads - added for UA SDK 1.1.

Thoughts on the OPC UA Information Model - blog entry by Matrikon's Eric Murphy.

Unified Architecture, Vista and OPC - by John Weber of Software Toolbox, published in the online Industrial Ethernet Book.

The Magic of OPC Unified Architecture - by OPC Foundation President Tom Burke, published in the online Industrial Ethernet Book.

Unified architecture - The future of OPC - by OPC Foundation Technical Director Jim Luth, published by ControlGlobal.com.

OPC Foundation's newsletter, OPConnect, regularly carries features on the Unified Architecture: see Issue 5 (October 2005) and Issue 4 (September 2005).