Design of a query language for accessing Spatial analysis in the web environment

Abstract

A spatial query language called SQL/Spatial has been designed to support the expression of user requests dealing with a variety of GIS analysis functions (e.g., map overlay and buffer) in the Web environment. Using the familiar SELECT - FROM - WHERE statement instead of procedural commands like macro language in some GIS packages, users can formulate their queries more easily, while conducting powerful spatial data retrieval and analysis. The language investigates an appropriate structure to express spatial queries within the framework of the on-going SQL standards for spatial extensions (i.e., Open GIS Simple Features Specification for SQL and SQL3 MultiMedia Specification Part 3: Spatial). By restructuring the FROM clause via a subquery, SQL/Spatial is well adapted to the general spatial analysis procedure by using current GIS packages, while conforming well to the SQL design concepts. The interface (client) of the language resides with a Web browser, while the query is processed by a query server. The query server, linked to the Web server via Common Gateway Interface (CGI) scripts, is composed of a query processor, Spatial Database Engine (SDE) and MapObjects Internet Map Server. It was demonstrated that the design of SQL/Spatial facilitates the access to spatial analysis functionalities on the Web.