Query Models and Languages for Geographical Information Systems

This paper presents a synthesis on the query models and languages to manipulate a geographical database. We present the different classes of query languages : based on predicates, based on operators without composition and based on operators with composition. We analyze the consequences on the data model, on the expressive power and on the query modeling. The introduction of operators as query primitives requires the closedness of these operators on geographical data. The introduction of operators increases the expressive power allowing queries involving a composition of operators. As a path operator (with the same arguments) provides several answers and may appear several times in a query, the query modeling must provide such an opportunity. Depending on the required expressive power, we present the different classes of interfaces at the user's level.