**3.2.2 The Knowledge Layer**

Knowledge representation has been described in five distinct roles it plays in (Davis et al., 1993). Those roles are

	- The representation's fundamental conception of intelligent reasoning
	- The set of inferences the representation sanctions; and
	- The set of inferences it recommends

With these roles in view, different languages that represent the knowledge have been conceived over the time. They vary in terms of their characteristics, expressive power and computational complexity. The effectiveness of any representation language can be measured in:


knowledge model because they decide the reliability of the model. If any model contains statements which contradict with each other, the model cannot be considered reliable. For an example A cannot be a father and son of B at the same time. Such statements should be rigorously audited for the model to be reliable enough.

 The semantic within the model should not be ambiguous. The meaning of each statement within the model should be clear and unambiguous.
