This book is written for software engineers, software project leaders, and software managers who would like to introduce a new advanced software technology, expert systems, into their product. Expert system technology brings into programming a new dimension in which "rule of thumb" or heuristic expert knowledge is encoded in the program. In contrast to conventional procedural languages {e. g., Fortran or C}, expert systems employ high-level programming languages {Le., expert system shells} that enable us to capture the judgmental knowledge of experts such as geologists, doctors, lawyers,...