ES (Expert Systems) is a important application field of AI (Artificial Intelligence). Its theory and technique have become more and more mature after several decades years. And its application has also been developed quickly.This paper has seven chapters. Firstly, the paper has introduced the basal concepts, characteristic and structure of ES. Then, the main techniques used in ES, knowledge expression and inference strategy, have been expounded. Soon afterward, based on all above theory, the article has discussed the design and realization of "Sewerage Disposing System". Finally, the trends of ES technology are pointed out. |