Origins of OPC

OPC was originally defined as a uniform solution to the recurrent task of connecting PC-based applications - particularly SCADA (Supervisory Control and Data Acquisition) and HMI (Human-Machine Interface) systems - to process peripherals.

The newly founded OPC Task Force met for the first time in May 1995. In December of the same year, the first draft specification of Data Access 1.0 was published. By 2006, just 10 years later, OPC had developed into a worldwide standard for the exchange of data and information between software components.

With over 7,500 OPC products and millions of installations in a variety of industries, the OPC initiative can be considered a complete success. Today, OPC comprises a number of specifications for various usage scenarios.

OPC is no longer merely a substitute for proprietary communication drivers for connecting SCADA systems and visualization programs to process peripherals. Today, process control systems, PC-based controllers, MES and even ERP systems are inconceivable without an OPC interface.

The OPC interface is not just used to transfer process data or individual parameters. Instead, entire ERP documents, parameter sets, control sequences, video signals and drive programs can be transported via OPC.

• OPC is a standardized software interface.
• OPC considerably minimizes the effort involved in software development and maintenance.
• OPC is powerful, flexible and user-friendly.
• OPC is established around the world with millions of installations.
• OPC is object-oriented.
• OPC follows the client/server approach
• OPC enables communication between several servers and clients at the same time.
• The OPC client and OPC server can run on the same or different computers.
• OPC enables remote access via DCOM or XML/HTTP.
• OPC defines various specifications for a wide range of uses.
• OPC is organized through the OPC Foundation.

Software manufacturers, too, only need a single driver connection: the OPC client interface. This offers advantages to both manufacturers and users.

How can users benefit from OPC?
In the past, the selection of drivers for individual automation components was usually limited. After all, drivers can't be developed for all proprietary interfaces. Today, OPC is making it possible for users to combine any visualization or control system with the hardware (such as a PC card) of their choice.

The increased quality of the drivers and OPC servers is another advantage. Thanks to the smaller number of drivers, manufacturers can concentrate on a single OPC server. This gives rise to additional functionality, and it's much more convenient for users. Furthermore, conformity tests carried out by special working groups of the OPC Foundation also contribute to the higher quality of OPC products.

Previously, proprietary drivers could often only be used with a single application. But through the OPC interface, users can access the OPC server with several OPC clients right from the start. This offers a more flexible way of accessing the functionality and data of OPC servers. This multi-client capability is effective locally on a PC, but it can also be used remotely in distributed networks through Distributed COM or XML/HTTP.

For example, a visualization system running on an office computer can be connected via a LAN to the OPC server on the factory floor without the need for additional driver software.

The more recent OPC specifications include XML and Web services so that OPC products can also communicate over the Internet through firewalls and can be used on non-Windows operating systems.