Validation and Verification : Validation

A validation check is an automatic check made by computer software to ensure that any data entered into the computer is sensible. There are many different methods of validation. The most appropriate method(s) to use will depend upon what data is being entered. The most common methods are listed here.

Validation Checks
Presence Check Checks that data has been entered into a field and that it has not been left blank. e.g. check that a surname is always entered into each record in a database of addresses.
Type Check Checks that an entered value is of a particular type. e.g. check that age is numeric.
Length Check Checks than an entered value e.g. surname is no longer than a set number of characters.
Range Check Checks that an entered value falls within a particular range. For example the age of a person should be in the range 0 to 130 years.
Format Check Checks that an entered value has a particular format or pattern. e.g. a new-style car registration number should consist of a letter followed by 1 to 3 numbers followed by 3 letters.
Table Lookup Check Checks that an entered value is one of a pre-defined list of valid entries which should be allowed.
Check Digit A check digit is a digit attached to the end of a string of digits. It is calculated from the other digits and used to help ensure that the whole string is inputted correctly.
Parity Check Used in data communications to ensure that data is not corrupted when it is sent down a transmission medium such as a telephone line.
Batch/Hash Totals Batch or hash totals are used when data is entered into the computer in batches to ensure that the data is entered accurately and no data is missed out.

Validation checks can be performed by any piece of software. However you are most likely to encounter them when creating a new database. Sophisticated database packages will let you implement validation checks using validation rules. You can provide different validation rules for each different field in the database.

GCSE ICT Companion 04 - (C) P Meakin 2004