地图符号库系统不仅是地理信息系统中不可缺少的基础功能模块之一，也是GIS的一个重要研究课题。
The Map Symbol Base System is not only one of the basic functions of Geographic Information System, but also an important research issue in GIS.
地图符号库系统是电子地图系统中不可缺少的功能模块之一。
The Map Symbol base System is one of the indispensable base functions in Electronic Map System.
标点符号是现代书面语中不可缺少的衔接和连贯标志。
Punctuation marks are an integrant sign of cohesion and coherence in modern writing.
地图要素与地图符号类型之间的关系长期被人们忽略。但它确是专题地图设计专家系统中不可缺少的重要环节，是地图符号设计的基础。
The relationship between map element and map symbol, which is the important key link of Thematic Map Design Expert System and the basis of map symbol design, has always been ignored.
地图要素与地图符号类型之间的关系长期被人们忽略。但它确是专题地图设计专家系统中不可缺少的重要环节，是地图符号设计的基础。
The relationship between map element and map symbol, which is the important key link of Thematic Map Design Expert System and the basis of map symbol design, has always been ignored.
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