Vague Relations in Spatial Databases

While qualitative relations (e.g. RCC8 relations) can readily be derived from spatial databases, a more difficult matter is the representation of vague spatial relations such as ‘near-to’,‘next-to’, ‘between’, etc. After surveying earlier approaches, this paper proposes a method that is tractable, learnable and directly suitable for use in natural language interfaces to spatial databases. The approach is based on definite logic programs with contexts represented as first class objects and supervaluation over a set of threshold parameters. Given an initial hand-built program with open threshold parameters, a polynomial-time algorithm finds a setting of threshold parameters that are consistent with a training corpus of vague descriptions of scenes. The results of this algorithm may then be compiled into view definitions which are accessed in real-time by natural language interfaces employing normal, non-exotic query answering mechanisms.