基于“3S”的甘肃省苜蓿病害诊断专家系统的知识获取与表示

知识获取和知识表示是构建专家系统的核心环节。在知识获取方面采用了基于“3S”（地理信息系统GIS、遥感RS、全球定位系统GPS）的半自动获取方式，这一方式结合了人工获取和自动获取的优势，提高了苜蓿Medicago spp.病害诊断的准确性。同时，应用“3S”技术把传统的关系数据库与具有空间属性的矢量数据关联起来，生成具空间属性的新知识库，增强了苜蓿病害诊断的可靠性，更加有利于苜蓿病害知识库的及时更新。在知识表示方面，则采用传统的产生式(If-Then)表示法，表示方式自然、简洁，易于广大基层农业人员所理解和接受，增强了苜蓿病害诊断专家系统实用性，有利于苜蓿病害诊断专家系统的推广应用，进而促进苜蓿产业的快速发展。

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.