An authority file is used to ensure that named people, places or other things can be connected in a dataset. For example, the name 'Alan Dix' might refer to the author of AI, HCI and statistics textbooks, or Alan Dix the theatre maker. An authority file would allocate each a unique identifier, say AlanDix_276493 and AlanDix_835672 and then these identifiers would be used in other data records to ensure it is clear which Alan Dix is being refered to. In pseudonomised data the identifier is deliberately chosen to be anonymous (unlike those in the example) and the authority file is either kept securely or deleted after use.