What is an expert? An artificial intelligence system that fits the type of systems based on knowledge. A system must use knowledge to generate all solutions for which task it was designed. What is an intelligent diagnosis system? A particular case of the expert system. What is right? The rules are used to represent knowledge Heuristic, providing a set of actions on data, verifiable. Developing an expert system consists of defining a set of rules that will lead to solutions. A rule consists of history (part conditional, LHS left-hand side – the left) and consistent (the actions RHS right-hand side – the right). History contains a set of conditions (conditional elements) that must be satisfied for the rule is applicable. But a fact? The basic form of representation for the Clips knowledge. The facts are organized into lists of facts. A fact can be specified by index or address. When one is added to the list of facts or receives as a unique index in the list of facts. Index of facts starting from scratch and incrementează with every new one is added or changed. When calling reset or clear orders index is set to zero. Operations that can make the facts are: * adding new facts to the list of facts; * removal of facts from the facts, that an amendment * * duplication of fact. Facts are of three categories: a) ordered, consisting of a symbol followed by a sequence of zero or more fields separated by spaces and bounded by parentheses “()”. b) neordonate consist of an abstract structure (similar to structure of C) in which each field has a name. c) initial facts using manufacturer deffacts may be placed in the collection of facts for facts using the command reset.