Knowledge acquisition and expression in 3Sbased expert system for alfalfa disease diagnose

The knowledge acquisition and expression is the coral step to build up expert system. The semiauto knowledge acquisition method based on 3S (Geography Information System, Remote Sensing, Globe Positioning System) was used, which combined advantages of the manual method and automatic method for knowledge acquisition so that the accuracy of alfalfa disease diagnosis could be improved. Meanwhile, the traditional database and vector data with spatial attribute were associated by 3S technologies, then it generated a new knowledge database with spatial attribute, and this enhanced reliability of alfalfa disease diagnosis, and it was more advantageous to update the knowledge base in time. In the knowledge expression, the traditional If-Then regulation was used, which was natural, simple, and closer to people's thinking and easy for local technicians to understand. And it was helpful for the extension of Alfalfa Disease Diagnosis Expert System and then the development of alfalfa industry.