Knowledge is the ability to form mental models that describe objects by combining instincts, ideas, rules, and procedures to form an action or decision. Knowledge can be classified into 3 first, procedural knowledge which relates to how to know to do something, then declarative knowledge to know whether something is right or wrong, and the last is tacit knowledge which cannot be expressed in language.
Knowledge is the key to an expert system if the algorithm combined with the data structure will produce a good program then in the expert system knowledge will be combined with conclusions. The hierarchy of knowledge starts from data that is still not clear, then the facts are searched for the truth so that it becomes valid information. Then you will get new knowledge from previous knowledge which results in knowledge and expertise to present knowledge.
Knowledge representation is used to encode knowledge in the expert system in order to capture problem information which will then be sought for a solution in the form of problem solving procedures. Knowledge representation is used by programmers to solve problems which will then be translated into programming languages by paying attention to other knowledge facts so that they can be used for reasoning.
