A Pictorial Query-by-Example Language

A symbolic image is an array representing a set of objects and a set of spatial relations among them. Symbolic images and related structures have been used in a number of applications including Image Databases, Spatial Reasoning, Path Planning and Spatial Pattern Matching. In this paper we describe a Pictorial Query-By-Example (PQBE) language aimed at the retrieval of direction relations from symbolic images. As in the case of verbal Query-By-Example, PQBE generalises from the example given by the user, but instead of having queries in the form of skeleton tables showing the relation scheme, we have skeleton images which are themselves symbolic images. PQBE provides an intuitive interface for use in geographic applications because of its close correspondence with the structure of space.