What is data validation?

We validate certain types of data by testing according to a particular set of rules.  For example, given a Zip Code and an associated city name, we can easily validate each against the other according to our database.  Likewise for valid street names within an area, and for items such as URLs, email addresses, 10 or 13-digit ISBNs for books, SIC and NAICS codes, etc. 

We can also do partial validation, for example against lists of proper names, organization names against a directory, product or technology terms, or special entities according to validation rules you might provide.