Simple Call Interface API
Two different interfaces to system:inmation exist at the moment. The Simple Call Interface API (or SCI) consists of a set of C# DLL’s that can be used by any external application. The Web service serves as a simpler interface to system:inmation, which uses HTTP/TCP calls (covered in the next chapter). Both interfaces have a similar scope meaning that similar tasks may be performed. In the following section the SCI is explained in detail including security aspects and examples.
The Simple Call Interface API (or SCI) consists of a set of C# DLL’s which can be used by any external application, either RESTful or not. It’s primary purpose is to serve as a simple interface for external C# applications to system:inmation. The currently supported scope includes:
Secure reads from any VQT item hosted in a system:inmation object namespace
Secure writes to any VQT item hosted in a system:inmation object namespace
Secure queries of any VQT item hosted in a system:inmation object namespace configured for data historization
In order to read data, the external application uses the ReadValue function. In order to write data the appropriate WriteValue function is used.
The SCI is split into two parts:
Stateless programming, for applications with short lifetimes
Stateful programming, for use in long running applications that benefit from using multiple threads, event based communication and internal caching in the SCI library
Stateless calls are initiated by first creating the StatelessInterface() object and configuring the TCP connection.
With Stateful calls, the library needs to be initialized by calling the static method SimpleCallInterface.Start(), and disposed by calling the static method SimpleCallInterface.Stop(). These methods must only be called once each, at the beginning and at the end of the application’s lifetime.
Prior to using any 'read' or 'write' method, the connection with the inmation server should be configured using the static method SimpleCallInterface.Initialize(). An already established connection to the inmation server may be terminated using the static method SimpleCallInterface.Dispose(). Both methods may be called multiple times.
The SCI library can be used for applications which run inside Microsoft Internet Information Services to provide web-based access, or WPF, Windows Forms and Windows Service applications.