<P> A Validation rule is a criterion or constraint 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 Validation rule or check system still used by many major software manufacturers was designed by an employee at Microsoft some time between 1997 and 1999 . </P>
when does the validation rule check the entered data
after the data has been encoded onto an input medium