Validation Files are using the PG-File format and they are necessary inputs the simulation is expecting a performance indicator for the match between any simulation variable and the variables in the simulation.
The Validation Files are linked by the information that is stored in the Sim-File.
They are defined the first time when Validation of time series are enabled in the Validation sheet of the document menu
Please note that the Validation file will have a format with time and value for each variable. The duration for the measured validation variable and the estimated error for the validation variable can be specified in the Simulation document