空间信息要素模型可视化的设计模式与应用

GIS系统的实现是一个相当复杂的过程,分层次模块化的方法被广泛采用,同时应用设计模式更加简单方便地重复使用成功的设计和体系结构,更有利于GIS系统的开发和重构。本文通过对描述地理信息系统空间信息模型中要素模型的几何体结构分析,充分运用和组合各种设计模式,在要素可视化设计和实现中,探讨要素组织采用组合模式与访问者模式相结合的形式,实现异构几何体的聚集访问;要素可视化的实现总体上采用合成模式与绘制采用策略模式相结合的形式,实现要素与绘制的有机分离及各种绘制形式的充分支持。这种结构的好处在于不但能很方便地实现Open GIS中有关要素几何体的抽象规范和相应的实现规范,而且能使系统结构清晰、模块分明,组织自然,有利于系统的开发、维护和扩展。

Research of Design Pattern on Visualization of Feature Model

As the realization of Geographical Information System (GIS) is a quite complicated course, the method of modeling and hierarchical structure is used widely. Furthermore, the applied design pattern makes it easier and more convenient to use successful designs and software architecture repeatedly than ever before, which benefits the development and reconstruction of GIS. The thesis, through the analysis of geometry model architecture of Geographical Information System feature model, fully uses and combines various kinds of design patterns to probe into the combination of composite pattern and visitor pattern together for feature organization, and makes it possible to access inhomogeneous geometry in geometry collects. Generally speaking, composite pattern and strategy pattern on rendering geometry for feature visualization enable us to separate rendering from feature naturally and sustain various kinds of rendering during the development and implementation of visualization of geographic feature. Advantages of this kind of structure lie in not only satisfying easily OpenGIS abstract specification and implementing specification of simple geometry, but also keeping structure clearly and module democratized, and making the structure more flexible and natural. It is beneficial to the development, maintenance and expansion of the Geographical Information System.