Graqula-A Visual Information-flow Query Language for a Geographical Information System

Abstract

The query language Graquala, described and discussed here, is designed for a geographical information system. The basic map data structure to which Graquala has been adapted is a homogeneous raster-based structure of run-length-code (RLC) type. Because of the homogeneity of the map data structure, queries can be applied in a more or less generic way; that is, queries can be applied to all map data regardless of their type. For this reason it has been possible to design a visual data-flow query language that allows compound queries which can become quite complex. In this work, Graqula and some elements of its environment, including a brief overview of the basic map data structure, will be discussed.