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 系統(tǒng)中定義了一個模式語言描述,以線為基礎(chǔ)來描述圖形,并定義了圖形的屬性和運算,為該類圖形提供了一個高效的描述工具。