Explain about the Object Identity of object oriented analysis

Object identity is a feature of an object that differentiates the objects from all other objects in the applications. With this, objects can contain, or refer to other objects. Object identity can be created in three ways:  

1)  You can refer as memory address in programming languages.

2) By assigning identifier keys in the database. 

3) Or by user-specified names, used for both database and programming. 

In a complete object oriented system every object is given an identity that will remain permanently associated with the object instead of the object's state or structural transitions. The object identity is also independent of the location, or address of that object.  It provides the most natural modelling primitive to allow the "same object to be a sub-object of multiple parent objects".