Foundations of the Theory of Learning Systems (Enhanced Edition‪)‬

When we talk about learning, we always have in mind the existence of
a certain goal that has to be reached through the learning process. Very
often this goal of learning cannot be specified explicitly due to insufficient
a priori information. In other words, the goal of learning is not completely
defined. In the opposite case, that is, when the goal of learning is given in
an explicit form, there is no need for learning since such a goal can be
reached without any learning, for instance, by designing the system in
advance. The characteristic feature of learning is that the lack of a priori
information, that is, incomplete definition of the goal of learning, is compensated
by necessary processing of current information.