基于快照方式的面向对象模型探讨

TGIS(Spatial-TemporalGIS)是GIS的重要分支,是实现动态数字地球的关键技术。静态3DGIS的技术已基本成熟,而其加上时间维的4DTGIS的关键技术是时空数据库的建立及其操作,它们与时空数据模型有关,主要处理超海量数据的存取和查询。本文结合快照模型的简单易行性和面向对象模型的方便灵活性,同时避开快照模型的不一致性和冗余性,以及面向对象的复杂性,探讨基于快照方式的面向对象模型,是一种实用的TGIS数据模型。它在对时间属性的处理方面采用独到的方法,首先建立一个基数据,然后通过快照方式产生缓冲数据,经过比较形成一个以对象变化为主的带有时间戳的新数据层。这样,在数据存储方面,节省了很多空间;在查询分析方面,以对象变化分层的数据算法更容易实现。此理论方法有效解决了TGIS的“瓶颈”问题,并通过自动元胞机理论(CA)予以证明。

Rudimentary Research on Snapshot Based Object-oriented Data Modeling

Spatial-Temporal GIS is an important branch of GIS, which, in other words, is an inevitable tendency to realize dynamic digital earth with the essential technology. The technology of static 3D GIS is already well developed, but 4D GIS, i.e., traditional GIS plus temporal dimension, is still under the stage of theoretical study because its essential technology involves creation and manipulation of the temporal data base, which are related to temporal data base modeling, mainly dealing with storage and research of mass data. In this paper, it is a reasonable TGIS data modeling to combine simple and feasible snapshort modeling with convenient flexible object-oriented data modeling, while avoiding the consistent and redundant snapshort modeling and complex object-oriented data modeling. The paper adopts a special way in dealing with the attribute of time, which firstly creates a fundamental data, then produces buffer data through snapshot data modeling, finally forms a new data pool with time stab. By so doing a plenty of space is saved in data storage and it is easier to realize calculation of data, which is to divide store layers based on the varying objects. The theoretical approach efficiently settles the "bottleneck" of TGIS and has been substantiated through Automatic Cellar Theory.