One of the main topics in geographical information systems (GIS) research concerns the definition of high level visual query languages (Chrisman, 2002; Laurini & Thompson, 1992). This arises from the need to provide the user with a visual interactive tool for data manipulation and retrieval that is independent of the data’s physical organization. The use of standard query languages for spatial data handling (Rigaux, Scholl, & Voisard, 2001; Shekhar et al. 1999) has been hindered by the lack of appropriate language support. In fact, in visual query languages for GIS, a query can lead to multiple interpretations (Favetta & Aufaure-Portier, 2000).