NonLinear filter                                   
We came across the moment when the filtering problem can not be solved in an ordinary way with the filtering object. It is always possible to find such a problem, since life is a real miracle! Is it possible that entire our theory may fail? Do not worry, there is a solution (or one of the solutions).
Here is one of the scenarios:
 Put the brackets (real ones) on the filtering form and place the needed filtering objects (or your objects) within the brackets. This clearly demonstrates the expression which the user can have a specific view at.

If you do not like or you do not have any better idea, just go ahead…!
How to develop the non-linear filter?
                        1)       If your already know the problem, it should be incorporated into the filtering form.
                        2)       In the course of the filtering form utilization, we should improve it, superposing the existing filtering form.
                               It is more than sure that the user will, one day, come to some non-linear filtering request.