OPC Fundamentals

OLE is the acronym of Object Linking and Embedding. It is a technology provided by Microsoft offering the possibility to share information between applications and to provide a way to drive an application from another one.
Using such technology, it will be possible to improve the application functionalities based on the ones provided by another application.

DDE is the acronym of Dynamic Data Exchange. It is a Microsoft technology for exchanging information between two Windows applications according to a client/server model.

COM is the acronym of Component Object Model; based on a binary standard. It provides a way to ensure the interoperability between different processes without paying attention to the used development languages.
COM comes as an extension of the OLE technology. As a part of the operating system, it aims to provide a built-in standard component used to develop servers that offer various services to clients’ applications.
Using such technology, the software development will be more simple and more open, knowing that it is possible to consume existing services exposed by third-party COM servers.
With all these advantages, COM presents drawbacks. Among them, we can introduce the limitation of COM deployment on a Windows platform.

DCOM is the acronym of Distributed COM. It is a standard developed by Microsoft as an extension of the COM technology to offer the possibility to share data between different objects through the network.

OPC is the acronym of Ole for Process Control. It is a standard of interfaces based on COM/DCOM technology. This standard aims to provide interoperability in communication between software applications that supervise industrials equipments.
A typical OPC architecture is based on two components: an OPC server to handle communication with the equipments and an OPC client to read/write data from/to OPC server (from/to the equipment).

OPC Server is a software application that drives bi-directional communication with the equipment such as PLC, a database (DB) or any data source and expose collected data to the OPC Client.

OPC Client is a software application used to access (for reading and/or writing) information provided by the OPC Server through the OPC standard.

If you need additional definition or clarification, please do not hesitate to contact me at hassen.kouki@gmail.com.