Virtual data sources
In addition to the physical data acquisition the function of the virtual data acquisition is also important. Virtual data are the data obtained inside the system both independently and on the basis of the physical data. Practically, the virtual data formation mechanisms are implemented in conjunction with the mechanism of user computing. Among the industrial controllers and SCADA-systems the different programming languages are used. In the case of controllers such languages can be for example low-level languages (assemblers), but in recent years the high-level languages (C, Pascal and others) are increasingly used, as well as the formal languages of IEC 61131-3 (sequential function chart SFC, function block diagrams FBD, LD relay circuits and text ST, IL). In the case of SCADA-systems, the computing is often provided with the help of high-level programming languages and formal languages.