High Quality Content by WIKIPEDIA articles! A Validation rule is a criterion used in the process of data validation, carried out after the data has been encoded onto an input medium and involves a data vet or validation program. This is distinct from formal verification, where the operation of a program is determined to be that which was intended, and that meets the purpose. The method is to check that data falls the appropriate parameters defined by the systems analyst. A judgement as to whether data is valid is made possible by the validation program, but it cannot ensure complete accuracy.