Orientation and Qualitative Angle for Spatial Reasoning

Though arrangement knowledge is well suited for qualitative representations of spatial situations, if we only use this kind of knowledge, we cannot do interesting inferences about relative positions of points in the plane. For example, if we know the orientation of two triangles over four points, we cannot say anything about the orientation of the other two triangles. In this paper, we show that the augmentation of arrangement knowledge by qualitative angles leads to interesting and useful inferences.