The Validation rule or check system still used by many major software manufacturers was designed by an employee at Microsoft sometime between 19.
The method is to check that data follows the appropriate parameters defined by the systems analyst.
For example, a US phone number should have 10 digits and no letters or special characters.
Code and cross-reference validation includes tests for data type validation, combined with one or more operations to verify that the user-supplied data is consistent with one or more external rules, requirements, or validity constraints relevant to a particular organization, context or set of underlying assumptions.
Rules can be collected through the requirements capture exercise.
This can only be achieved through the use of all the clerical and computer controls built into the system at the design stage.
For example the delivery date cannot be before the order date.
Checks to ascertain that only expected characters are present in a field.
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.