A Pictorial Query Language for Querying Geographic Databases Using Positional and OLAP Operators

The authors propose a declarative Pictorial Query Language (called PQL*) that is able to express queries on an Object-oriented geographic database drawing the features which form the query. These features refer to the classic ones of a geographic environment (geo-null, geo-points, geo-polyline, and geo-region) and define the alphabet of the above mentioned language. This language, extended with respect to a prevoius one, considers twelve positional operators and a set of their specifications. Moreover, the possibilty to use the mentioned language to query multidimensional databases is discussed. Finally, the characteristic of the mentioned language by a query example is shown.