TABLE OF CONTENTS A modern automation system needs more than just configuration and monitoring capability. Software infrastructure has therefore become an increasingly important criterion in recent years for selecting an automation system. Because the applications have to work together, an open software architecture is even more important.
Software is the operator display, but software also handles advanced control, data logging, reports, etc.
Different plant people need different information. Software is a key part in the information architecture, displaying process variable readings to operators and computing key performance indexes to managers. Standard software interfaces permit applications to exchange data.
Several technologies are involved in open software architecture (see Figure 29-1). In a client-server scheme, a client application displays data from a server application such as a database or hardware source. A basic client-server interface is in the Windows operating system provided by Microsoft's Component Object Model (COM), extended by Distributed COM (DCOM) between networked computers. To provide simpler browsing and exchange of live automation system data, such as process variables, the OLE for Process Control-Data Access (OPC-DA) technology was developed by the OPC Foundation. Some software, particularly non-automation software, still rely on an old Windows technology called Dynamic Data Exchange (DDE) for live data exchange, but it is not as fast or easy to use as OPC. Alarms and events are propagated between applications using the OPC-A&E subscription and filter technology. Database engines are used to store configurations and historical plant data.
