摘要： 数据库是地理信息系统（GIS）的基础。复杂的GIS应用要求它对用户定义的数据类型和操作具有扩充能力。该文针对用于GIS的可扩充数据模型存在的问题。构造了一个适合地图数据库应用的可扩充数据模型。它以嵌套关系模型为基础．引入高阶算子定义操作。这些算子不但增强了代数操作的能力，而且利用它们能方便地扩充用户定义的几何操作、地图量真和几何变换。该模型具有较强的扩充能力，可以作为设计可扩充地图数据库系统的基础。

关键词: 可扩充数据模型, 地图数据库, 高阶算子

Abstract: Database is the basis of geographical information systems(GIS). Complicated GIS applications require it to be extensible for useredefined data types and functions. To attack the problems on the extensible data model for GIS applications, we propose an extensible data model for map database applications in this paper. It is based on the nested relationaldata model, and employs high-level operators to define algebraic operations. These operators not noly enhance the power of algebraic operations, but also make it easily to incorporate user-defined geometric functions and map measurement functions. It can serve as a foundation of designing extensible map database systems.

中图分类号: 

• P208