The Syntactic and Semantic Correctness of Pictorial Configurations to Query Geographic Databases by PQL

In the field of geographic information systems, one important issue is related to define a sound method of syntactic and semantic correctness analysis for queries which can lead to multiple interpretations for the system and for the user. In this paper, we propose an approach in order to determine the exact syntactic and semantic interpretations of geographic configurations that are involved in queries for a pictorial query language. This language, called PQL, supports interactive manipulation of geographic elements letting users directly to express a query by drawing. We put in evidence and underline allt he syntactically correct pictorial configurations among geographic objects which represent the topological relationships. Then, upon such analysis we determine the semanti correctness of configurations depending on the stored geographic data, and the detection of the ambiguities. We propose different solutions to determine the semantic correctness integrating the result of such approach to the set of PQL operators. Finally, we show the capability of such approach to resolve the ambiguities which arise from the formulation of complex queries involving multiple geographic objects.