Knowledge Level Learning

In Prolog-EBG the $h$ follows (logically) directly from B alone, independent of D. So, why do we need examples?
Examples focus Prolog-EBG on generating rules that cover the distribution of instances that occur.
So, will it ever learn to classify an instance that could not be classified by B?
No. Since $B \entails h$ then any classification entailed by $h$ is also entailed by $B$.
OK, so this this a problem with all analytical learning methods?
No. For example, let B contain a statement like
GrandDaughter(sister(x),spouse(y)) ← GrandDaughter(x,y)
This rule does nothing until we have one example, then it might identify added GrandDaughter().
Another example is provided by assertions known as determinations. If we are trying to identify "people who speak Portuguese", a determinant might be
The language spoken by a person is determined by their nationality.