History of OPC
The need for OPC is probably best traced back to the introduction of Windows 3.0 in 1990. With Windows 3 it became possible, on an inexpensive, mainstream computing platform, to run multiple applications simultaneously. Even better, Windows provided a standard mechanism for those applications to exchange data at runtime. This mechanism was Dynamic Data Exchange, or DDE, and it was not long before users saw the benefits of having their process or plant data 'piped' into general purpose applications like Microsoft Excel.
Soon however, the limitations of DDE became clear. It was not terribly robust, there was no support for DDE across a network, and, worst of all, its bandwidth was very limited.
A number of notable attempts were made to rectify these shortcomings, of which Wonderware's InTouchTM SCADA software had the greatest impact. It introduced a means of networking DDE traffic (NetDDETM, which was later taken up by Microsoft), and also greatly increased the effective bandwidth of DDE by packing multiple data items into each packet or message (FastDDETM). The main drawback of this scheme, and others such as Rockwell Software's AdvanceDDETM, was that they remained proprietary, requiring payments to their inventors, and thereby guaranteeing that they would never attain the status of a true industry standard.
When OLE 2.0 was launched in 1992, it was apparent that it would eventually replace nearly all uses of DDE. It was more flexible, more robust, and used more efficient transport mechanisms.
Around the same time, a group calling itself WinSEM (Windows in Science, Engineering and Manufacturing) began meeting at Microsoft's Redmond headquarters. This group's members were largely from the areas of industrial control and data acquisition, with Microsoft acting as a catalyst.
By 1994, there was firm interest, focused through WinSEM, in the use of OLE techniques for moving process data between applications in (almost) real-time. In particular, a number of SCADA vendors saw the chance to standardize the interface between the SCADA core and the device drivers which were actually responsible for acquiring the data. Potentially, this could benefit both SCADA vendors and equipment manufacturers: the SCADA vendor would not need to invest valuable effort in writing drivers, while the equipment manufacturer would have to provide only one driver which would work with all Windows software.
The most interesting proposal was submitted by US Data in March 1995. Seen next to the released OPC specification, this document now appears ludicrously simplistic. However, most of the key concepts of OPC were already in place.
After the publication of this promising document, progress towards a standard was, sadly, very slow. It was the view of a number of the those involved in the WinSEM effort (including Microsoft) that a smaller, more tightly focused group would be needed to ensure timely delivery of a standard. This was the origin of the OPC Task Force.
The OPC Task Force went public at the 1995 ISA Show in New Orleans with a news release. Its members consisted of Fisher-Rosemount (now Emerson Process Management), Intellution (now part of GE Fanuc), Intuitive Technology (now part of Wizcon Systems), OPTO 22, and Rockwell Software. Microsoft was to be involved in a supportive and consultative role.
The first draft version of the OPC specification was released in December 1995, and was presented to the last WinSEM gathering (to date) in Redmond in January 1996. Despite a certain amount of pique due to the initial perception that an elite group had run away with the standardization effort, the overall response was quite favorable and very constructive.
A second draft specification followed in March 1996, and 'JumpStart' seminars were held in Dallas, Texas (April 1996), London, England (July 1996), and Japan (August 1996) to give interested developers a fast track introduction to the proposed standard.
The OPC specification version 1.0 was released on August 29 1996. A corrected version 1.0A of the OPC Data Access Specification, as it is now known, appeared in 1997.
Having sought opinion throughout the industry, a decision was taken that the OPC specification should be managed by an independent, non-profit organization to be called the OPC Foundation.
The OPC Foundation made its presence felt at the 1996 ISA Show in Chicago, with OPC server demonstrations from various companies at the Microsoft booth, and also the first General Assembly meeting of members. Further collaborative demonstrations have followed at major trade shows around the world.
Commercial products using OPC began to appear in late 1996. By mid-1998, the widespread support for OPC had confirmed it as the industry standard.
The Foundation has broad industry support (over 300 members in total), with off-shoots in Japan and China. It has its own website, www.opcfoundation.org.
OPC Data Access 2.0 was published in late 1998, and comprised separate specification documents for the custom and automation interfaces. The custom specification included a more robust 'advise on change' mechanism. The automation interfaces, meanwhile, were redesigned for improved ease of use, and to take advantage of technology improvements.
Also in late 1998, the scope of OPC was expanded with the publication of the Alarms and Events custom interface specification, version 1.0.
2000 was a vintage year for the OPC Foundation, with the publication of new custom interface specifications covering Historical Data Access, Batch and Security.
Arguably the most significant development of 2001 was the release of the OPC Foundation's Compliance Testing and certification program for OPC Data Access servers, which will soon be extended to cover Alarms & Events servers.
2001 also saw the release of the automation interface specification for Historical Data Access, and Batch custom interface specification version 2.0.
Little other progress was made during 2001. See our review, twelve months on, of the plans announced at Hannover Messe 2001.
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