Explain how you can define an object model of a system.

A list of terms that shall be used by end users to describe state and behaviour of objects in system.  

Different user classes may need different mental models of objects in the system.  This concludes:

Which type of objects there are (user objects). 

What information user can know about object of a particular type (user object attributes). 

How objects may be related to the other objects (relationships). 

Object types with 'subtypes' that have additional specialised actions or attributes i.e., User object, User object subtype, User object action, Container objects. 

A model of business objects which end users believe interact within a GUI system.