Querying by Sketch Geographical Databases and Ambiguities

This paper presents GSQL (Geographical Sketch Query Language), a sketch-based approach for querying geographical databases based on the GeoPQL query language. Geographic information is intrinsically spatial and can be conveniently represented using a bi-dimensional space. Graphical User Interfaces and Visual Languages can be used to satisfy this need. However, the growing availability of sketching tools (PDA, digital pens, etc.) enables a more informal and natural user interaction. Sketch based interaction is very effective. Each user can easily sketch his/her geographical query by drawing it, erasing and modifying its parts and highlighting the query target. A query is the expression of the configuration of the expected result. Sketch recognition and query interpretation (and solution of their ambiguities) starts from a context- independent approach and uses the characteristic application domain information. Context-independent sketch interpretation uses spatial and temporal information related to the sketching process. Context-dependent sketch interpretation uses geographic domain information to solve the remaining ambiguities and correctly interpret the drawing and query. An analysis of the ambiguities characterising object sketching in the geographic application domain and their possible solutions are presented herein. Each query identifies the set of geographical objects involved and the target; the query interpretation must unambiguously identify the set of its results.