Database Model and Algebra for Complex and Heterogeneous Spatial Entities

Abstract

Current Geographic Information Systems (GISs) adopt spatial database models that do not allow an easy interaction with users engaged in spatial analysis operations. In fact, users must be well aware of the representation of the spatial entities and specifically of the way in which the spatial reference is structured in order to query the database. The main reason of this inadequacy is that the current spatial database models violate the independence principle of spatial data. The consequence is that potentially simple queries are difficult to specify and strongly depends on the actual data in the spatial database.

In this contribution we tackle the problem of defining a database model to manage in a unified way spatial entities (classes of spatial elements with common properties) with different levels of complexity. Complex spatial entities are defined by aggregation of primitive spatial entities; instances of spatial entities are called spatial grains.

The database model is provided with an algebra to perform spatial queries over complex spatial entities; the algebra is defined in such a way it guarantees the independence principle and meets the closure property. By means of the operators provided by the algebra, it is possible to easily perform spatial queries working at the logical level only.