In most instances, a thorough validation of the ages of extremely old people can only be done by accessing personalized information. For example, the name of a person is needed to match census information with birth, marriage, or death certificates. Contributors to the IDL are required to observe all data privacy regulations in their countries and to allow only specially trained personnel to perform age validation. No personal information is supplied to the public version of the IDL, and any such personalized information is not made available to researchers or other individuals not involved in the validation process.