Determine the level of state decomposition

The level of state decomposition must be determined by judgement. A too fine grained model is unsuitable, such as, modelling all possible ages of an employee as individual states. Also, a gross decomposition is ineffective, for illustration, modelling an employee as employed or not. 

You can ask whether all objects of world have behaviour which can be modelled.

Of course, not all the objects have behaviour worth modelling. Consider the example from field of object oriented nursery rhymes, sad story of Humpty Dumpty. Clearly, you will not like to model such examples.