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.