Geo-query: A Geo-object oriented query system integrated with Oracle for GIS
Zhong Zhenxiang, Lu Zhonghui
Dept. of Computer Science,
Peking University, Beijing, China
Zhou Xintie
National Remote Sensing Centre of China
Abstract
This thesis discusses the design of the spatial object-oriented query interface integrated with the relational database management system ORACLE in a Geo-Information System (GIS) Geo-union. The integrated query interface not only relates to the spatial relations between the objects, but also relates to the textual attributes by which the objects are characterized in a relations database. The objects in spatial queries can usually be classified into three categories: point, lien and polygon. Based on this, six basic spatial relations among point, lien and polygon are analysed, and the design of a Geo-object oriented Query Languages (GQL) and a graphical interactive man-machine query interface are presented. The GQL uses an object identifier to connect the spatial information of a object with the textual attributes of the object stored in RDBMS (ORACLE). By adding the map overlay and clip operations in queries, the capability of the query interface is greatly reinforced.
Introduction
The GIS systems the information based on spatial objects (usually divided into points, lien and polygons) in varies kinds of subject maps. In a subject map, each spatial object has different kinds of information: the object's geometric structure and topological relations with other objects (e.g. a series of connected line-segments from a polygon). In addition, textual attributes, for example, an administration district name, the total population of district and the principal governor's name etc. can be attached to polygonal object. These kinds of information are represented in different forms in a computer. In a view of the GQL query system, queries often involve all of these kinds of information. Following example is a typical query:
"find the province names and the names of province governors, where their average annual incomes per person is greater the $300, and the Yangtze river passes through them."
In the sequel, firstly, six categories of spatial relations are discussed, nest the design of GQL is introduced and then the connection between GQL and RDBMS is described briefly, and finally the conclusion is given.
Six categories of spatial relations
- Relations between Point-object to Point-Object
- Nearest - Point Relation: Find the nearest point-object to the given point in a given map
- Farest-point Relation: Find the farest point-object to the given point in a given map.
- Point-buffer Relation: Given a point and a buffer size, find all point-objects, which lie within the buffer of the point in a given map.
- Relations between Point-objects to Line-Objects
- Common Point Line Relations: Given a Point, find all line-objects, which pass thru the same point.
- Nearest-to-Point Line Relation: Given a line, find all point-objects, which are lie on the line, in a given map.
- Lien-Pass-through Point Relation: Given a line, find all point-objects, which are lie on the line, in a given map.
- Nearest-to-Lien Point Relation: Give a line, find the point-object which is nearest to this lien I a given map.
- Side point Relation: Given a lien and a side (left or right), find all point-objects which are lie in the same side in a given map.
