OPC related knowledge
1. COM - Common Object Model Component Object Model
COM provides standards for communication and internal components. With COM, an actual application can use any other application object or operating system, or allow the upgrade of the software component without affecting the operation of the entire application system. Developers and system integrators can create custom solutions using COM. CoM is a binary standard, which is the core of DCOM, ActiveX, and OLE technology.
2. OLE - Object links and embedded
OLE is used to integrate between different applications, even between multiple types of information to achieve highly application compatibility. OLE technology is based on COM, and considers the development of reusable, plug-and-play objects, and these objects can be operated between multiple applications. OLE also specifies reusable, component-based software development specifications, so that any software vendor can write software components in any language in such software development.
3. Ole Automation - OLE Automation
OLE Automation and derived COM technology are designed by Microsoft to allow components (written with C or C ) by the client (written with Visual Basic or Delphi). This model can meet the needs of the process industry because hardware developers can write software components that are data access to the device with C or C . With OPC, the developer of the application can write program code in any language, and is used to request and use the factory layer data.
4. DCOM - Distributed Component Object Model
DCOM extends COM's technology to the network (remote object). This is a highly optimized new protocol that allows remote components to look like locally. The first release of Windows NT 4.0-based DCOM is in August 1996. Microsoft's Java and VB scripts support DCOM and ActiveX development. Other companies are developing different DCOMs and ActiveX scripts for non-Microsoft platforms.
5. ActiveX
ActiveX is an update and upgrade for widely used OLE control technology, depending on COM technology, is the rename and reconstruction of OLE control technology. It is an object-based technology rather than object-oriented technologies. ActiveX is an open, integrated platform that allows program developers, webmakers to make portable applications and interactive content for Internet (WWW). ActiveX is an open technology for different platforms to get Mac, Windows, and UNIX systems.
6. DDE - Dynamic Data EXCHANGE
DDE is the predecessor of OLE technology, is a method of dynamically moved data between applications developed on Microsoft Win32 Application Interface (API). The DDE protocol transmits information between applications, allowing application to share data and use shared memory data. The application uses the DDE protocol to transfer data while switching data, so that the application can update the data with each other, and thus the latest data is always the latest. Before the OPC technology, although it recognizes the need to develop software programs to connect to their hardware, they are subject to their ability to develop communication drivers because the selection of program development can only limit DDE and a dedicated DDE export. Table between tables. Select any DDE for program development, it is possible to restrict the user's choice of software, or hinder the user's acceptance of the hardware.
