Question

4.3 Explain the major OPC specifications, which belong to "OPC Common" of "Classic OPC

Answer 1

There are three OPC Classic specifications:

• OPC Data Access (OPC DA) defines OPC client-server technology and how software can read and write data, as well as the data types and structures available.
• OPC Alarms and Events (OPC AE) describes the ways OPC server software can monitor systems and send alarms to client software.
• OPC Historical Data Access (HDA) defines the queries and analytics that can be applied to the historical time-stamped data collected from devices

The original OPC Classic specification is OPC DA (Data Access), which defines an interface between client and server applications to exchange process and manufacturing data. Other important OPC Classic specifications include OPC Alarms & Events (OPC AE) and OPC Historical Data Access (OPC HDA).

OPC Classic continues to be an integral part of the OPC technology portfolio. In 2010, OPC Classic was enhanced with the OPC .NET 4.0 specifications to adapt to the new technical innovations of the Microsoft platforms providing better connectivity, reliability, security and interoperability.

In the world of automation security has become a major source of discussion and an important part of most systems. The OPC Foundation has for a long time support secure interoperability between systems made by multiple vendors, initially with its OPC DA, OPC A&E, OPC HAD and OPC Security interfaces (collectively now termed OPC Classic) and most recently with OPC Unified Architecture (UA). These two standards provide common functionality, but OPC UA unifies and enhances the functionality provide by the OPC Foundation Classic interfaces. These two standards provide, when consider from a security point of view, a somewhat different view of security and a very different manner of implementing the view.