From Regions to Transitions, From Transitions to Objects

Abstract

This paper describes the construction of a qualitative spa-tial reasoning system based on the sensor data of a mobile robot. The spatial knowledge of the robot is formalised in three sets of axioms. First of all, axioms for relations be-tween pairs of spatial regions are presented. Assuming the distance between regions as a primitive function in the lan-guage, the main purpose of this initial axiom set is the clas-sification of relations between images of objects (from the robot’s vision system) according to their degree of displace-ment. Changes in the sensor data, due to the movement either of objects in the robot’s environment or of the robot itself, are represented by transitions between the displacement rela-tions. These transitions are formalised by the second set of axioms. The predicates defining the transitions between im-age relations are connected to possible interpretations for the sensor data in terms of object-observer relations, this issue is handled by the third set of axioms. These three axiom sets constitute three layers of logic-based image interpretation via abduction on transitions in the sensor data.