In which we design agents that can form representations of the world, use a process of inference to derive new representation about the world and use these new representations to deduce what to do.

This chapter introduces Knowledge based agents. The concepts that we discuss the representation of knowledge and reasoning processes that bring knowledge to life are central to the entire field of AI.

Knowledge and Reasoning also play a crucial role in dealing with partially observable environments.

A Knowledge based agent can combine general Knowledge with current precepts to infer hidden aspects of the current state prior to selecting actions.Example: A physician diagnoses a patient – i.e. infers a disease state that is not directly observable – prior to choosing a treatment. Some of the knowledge that the physician uses in the form of rules learned from textbooks and teachers and some is in the form of patterns of association that the physician may not be able to consciously describe. If its inside the physicians head, it counts as knowledge.

Understanding natural language also requires in hidden state, namely, the intention of the speaker. When we hear, “John saw the diamond through the window and coveted it”. We know “it” refers to the diamond and not the window – we reason, perhaps unconsciously, with our knowledge of relative value. Similarly, when we hear, “John threw the brick through the window and broke it”. We know “it” refers to the window.

Reasoning allow us to cope with the virtually infinite variety of utterances using a finite store of common sense knowledge.

Problem – solving agents have difficulty with this kind of ambiguity because their representation o contingency problems is inherently exponential.

Our final reason for studying knowledge – based agents is their flexibility. They are able to accept new tasks in the form of explicitly described goals, then can achieve competence quickly by being told or learning new knowledge about the environment. And they can adapt to changes in the environment by updating the relevant knowledge.