The Post-validation action sends feedback to help enforce validation.Simple range and constraint validation may examine user input for consistency with a minimum/maximum range, or consistency with a test for evaluating a sequence of characters, such as one or more tests against regular expressions.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.These additional validity constraints may involve cross-referencing supplied data with a known look-up table or directory information service such as LDAP.For example, an experienced user may enter a well-formed string that matches the specification for a valid e-mail address, as defined in RFC 5322 but that well-formed string might not actually correspond to a resolvable domain connected to an active e-mail account.
It uses routines, often called "validation rules" "validation constraints" or "check routines", that check for correctness, meaningfulness, and security of data that are input to the system.
The difference between data validity and accuracy can be illustrated with a trivial example.
A company has established a Personnel file and each record contains a field for the Job Grade. An entry in a record may be valid and accepted by the system if it is one of these characters, but it may not be the correct grade for the individual worker concerned.
Rules can be collected through the requirements capture exercise.
In evaluating the basics of data validation, generalizations can be made regarding the different types of validation, according to the scope, complexity, and purpose of the various validation operations to be carried out.