This implies that the discernibility function f(B) computes the minimal sets of attributes required to discern any equivalence class from all the others. Similarly, the relative discernibility function f(E, B) computes the minimal sets of attributes required to discern a given class E from the others.
For the example above, the following relative discernibility functions can be calculated:
From the example, over the set of classes the attributes values for the attributes education and works go hand in hand. Whenever education is good, works is yes, and whenever education is poor, works is no. Thus, IND(C) = IND() = IND(). The only indispensable attribute in our example is studies.