Solving spatial analysis problems with GeoSAL, a spatial query language

Database query languages are commonly used as a tool to retrieve data of interest from databases. Although some query languages provide basic functions useful for statistical data analysis and others contain spatial query capabilities, there is as yet no query language which satisfies even basic requirements of spatial analysis. By including a set of fundamental spatial operators into the query language of an extensible DBMS, a number of typical spatial operations in GISs can, however, be formulated as queries in the language. Hence, in the future spatial analysis tasks could be carried out by using such a query language, relieving users from procedural programming while retaining the advantages of a systematic language structure embedding fundamental as well as domain-specific concepts. This paper shows how to perform spatial queries and analyses with GeoSAL, a spatial query language designed for an extended relational DBMS, which is being developed at the National Defence Research Establishment in Stockholm. GeoSAL is based on an extended relational data model which integrates the object and layer models commonly found in GISs. Spatial data types and operators are part of the language. Examples given in this paper demonstrate the use of GeoSAL in modeling typical spatial operations and performing spatial analysis.