this system follows the principle of intelligent, open, hierarchical and specialized, utilizing knowledge furthest . here, knowledge contains parameters library, shapes library, rules library and human assistance . in this system, we define a pattern description language to describe shapes based on line we also define line's attributes and operations 系统中定义了一个模式语言描述,以线为基础来描述图形,并定义了图形的属性和运算,为该类图形提供了一个高效的描述工具。