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In [[computer science]], '''data validation''' is the process of ensuring that a program operates on clean, correct and useful data. It uses routines that check for correctness or meaningfulness of data that are input to the system.
The simplest data validation verifies that the characters provided come from a valid set. For example, telephone numbers should include the [[numerical digit|digit]]s and possibly the characters <tt>+</tt>, <tt>-</tt>, <tt>(</tt> and <tt>)</tt> (plus, minus and the parentheses). A more sophisticated data validation routine would check to see the user has entered a valid country code; the number of digits entered matches the convention for the country or area specified, etc.
Incorrect data validation can lead to [[data corruption]] or a [[software security vulnerability|security vulnerability]].
Data validation checks that the data are valid and sensible/reasonable before they are processed.
Methods used for validation are...
*'''Format or picture check'''
Checks that the data is in a specified format (template), e.g., dates have to be in the format DD/MM/YYYY.
*'''Range check'''
Checks that the data lie within a specified range of values, e.g., the month of a person's date of birth should lie between 1 and 12.
*'''Presence check'''
Checks that important data are actually present and have not been missed out, e.g., customers may be required to have their telephone numbers listed.
*'''Check digits'''
Used for numerical data. An extra digit is added to a number which is calculated from the digits. The computer checks this calculation when data are entered, e.g., The [[ISBN]] for a book. The last digit is a check digit calculated using a [[modulus]] 11 method.
*'''Batch totals'''
Checks for missing records. Numerical fields may be added together for all records in a batch. The batch total is entered and the computer checks that the total is correct, e.g., add the 'Total Cost' field of a number of transactions together.
*'''Hash totals'''
This is just a batch total done on one or more numeric fields which appears in every record , e.g., add the Telephone Numbers together for a number of Customers.
== External links ==
* [http://www.thevickerage.worldonline.co.uk/theteacher/newgcse/module5/task10.htm Data Validation]
{{Uncategorized|November 2006}}
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