The identity document is used to connect a person to information about the person, often in a database. The photo and the possession of it is used to connect the person with the document. The connection between the identity document and information database is based on personal information present on the document, such as the bearer's full name, age, birth date, address, an identification number, card number, gender, citizenship and more. A unique national identification number is the most secure way, but some countries lack such numbers or don't mention them on identity documents.