A text field such as a personal name might disallow characters such a markup-based security attack.An e-mail address might require at least one @ sign and various other structural details.
The method is to check that data falls 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.
Regular expressions are effective ways of implementing such checks.
(See also data type checks below)Checks for missing records.