Identity is the property of an object which allows it to be uniquely specified.

Identity allows you to specify a specific object or individual out of a group of objects or individuals.

For example: If Ann asks Bob to move a rock, she may specify the specific rock from rocks in the general area by:

  • pointing her finger at the rock
  • describing the rock's size, shape and color
  • giving map coordinates of the intended rock.

For people an ambiguous specification is a person's name which may not be unique. There may be more than one Ann or even more than one Ann Baker. For computer systems individuals are usually give a unique username, so that the use of a username is unambiguous.