Complex sentence: The verification and validation of a simulation model starts after functional specifications have been documented and initial model development has been completed; and requires the definition of a domain of applicability within which the model is executed to make predictions.
Split into simpler sentences: The verification and validation of a simulation model starts after functional specifications have been documented and initial model development has been completed. Verification and validation of simulation models requires the definition of a domain of applicability within which the model is executed to make predictions.