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OPC Unified Architecture

Introduction

Timescales

Specifications

Downloads

UA References

Introduction

Background to UA

OPC Unified Architecture (UA) is the next generation of OPC. The first parts of the specification were released August 2006. Full release is anticipated during the early part of 2007.

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.

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.

Collaboration

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:

2003-Q4

Architecture vision.

2004-Q1

UA Committee formed.

2005-Q1

Implementation sub-committee formed.

2005-04

First prototype specifications.

2005-10

First Release Candidate specifications.

2005-10

UA demonstration at ISA Expo 2005, Chicago, IL.

2006-04

Full set of draft specifications published.

2006-05

OPC Foundation launches dedicated Unified Architecture page.

2006-06

"Final" Release Candidate specifications published.

2006-08

First OPC UA Specification parts (1-5) reach Release status.

2006-09

OPC UA Specification part 8 (Data Access) released.

2006-10

Unified Architecture DevCon held in Munich, Germany

2006-10

Beta versions of Schema and WSDL documents for UA published.

2007-01

OPC UA Specification part 11 (Historical Access) released.

2007-01

OPC UA SDK for .NET available at beta level.

2007-02

OPC UA Specification part 10 (Programs) released.

2007-06

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.

The Outlook for UA

The UA development has been a major investment of effort. The scope of the project is huge, and failure would essentially mean the end of OPC Foundation as a body of influence - there is no going back from UA. Failure would also be a disaster for automation vendors and for industry generally: enterprise-wide standards of this type are desperately needed.

OPC Foundation has been wise, therefore, to take a cautiously sensible approach to the marketing of UA. Care has been taken not to raise expectations too high too soon. Fortunately, early indications are very encouraging: specifications appear solid, and a strong presentation and demonstration were made at the ISA show in October 2005 (see References, below).

Timescales

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

Specifications

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 (with a supplemental download containing Schema and WSDL definitions)
• Part 7: Profiles

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
• Part 10: Programs - released
• Part 11: Historical Access - released

A further part has been added more recently:

• Part 12: Discovery

Downloads

An OPC UA SDK for .NET is available at beta level, to OPC Foundation corporate members.

The SDK includes:

• Implementations of the XML Web Services and UA Native Binary stack profiles
• Server and Client development toolkits
• Sample Applications

The sample applications include source code. The stack and development toolkits are currently supplied as binaries only.

UA References

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.

Other Articles

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).