COM

The term OPC is an abbreviation for OLE for Process Control. OLE in turn is an abbreviation for Object Linking and Embedding which is a Microsoft programming technology based on the COM technology (Component Object Model). This long line of abbreviations is unfortunate but it is important to understand that OPC servers are built on COM technology.

COM is an ABI that allows an application to communicate to a software component. That software component can reside in the same physical machine or in another networked computer. In the latter case Distributed COM or DCOM can be used to provide the networking communications functionality. OPC uses COM technology to communicate between an OPC application (such as the MetaBridge application) and OPC servers.

Most of the time, Deployment Engineers will not have to worry about the COM details and simply install the OPC server and OPC MetaBridge on the same physical Windows computer. If required the OPC MetaBridge application can run on a separate computer and communicate using DCOM to the actual OPC server. The details of how this is achieved is outside the scope of this document. It is recommended that the MetaBridge application runs on the same computer as the OPC server as this greatly simplifies the network/software set up.