Communication, Event orientation

The processing of data and the forwardingbetweenthe individual processes (managers) in WinCC OA is event orientated normally. This means that only value changes are processed or forwarded immediately. On the contrary, without value changes, there is no communication or processing lload in steady operation.

Figure: Process of an event orientated communication connection

The system works very efficiently and is active "only on demand". The necessary structures are provided for the creator of an application. Corresponding to the communication role "Provider-Consumer" shown in the Client-Server / Provider-Consumer section, there are functions available, which enables a user software module or interface (consumer) to logon to value changes of a data source (provider). After successful logon (connect) each new value is forwarded automatically from the data source to the consumer and is processed.

The managers communicate via TCP/IP message interface. This secure and fully developed communication form also allows a data exchange beyond the computer and operating system limits. The worldwide usedstandard TCP/IP guarantees highest reliability, compatibility and performance.

If the SSL communication is used, the entries ip_deny and ip_allow can be omitted to specify access lists. The SSL certificates guarantee a secure communication.

An event orientated system normally has to process less data than a cyclic system of the same size. Even in case of the same data traffic the event orientation provides a much better reproduction of the real value developing mathematically. Resulting errors are minor to cyclic systems. Event orientated systems are also more suited for each form of tracking.