Qualitative Directions in Egocentric and Allocentric Spatial Reference Frames

Abstract

In this paper, we have presented a formalism for representation of and reasoning about directions in a qualitative way in two spatial reference frames, namely, an egocentric reference frame and an allocentric reference frame. Qualitative direction has been separated from dimensionality of spatial objects and as such, the formalism may be used to represent qualitative direction in a dimension-independent way. The formalism uses fewer numbers of base relations than existing formalisms and granularity can be refined easily. Algorithms for finding composition and converse of base relations have been presented. An example is presented to show how formal grammar can be used in conjunction with JEPD sets of qualitative relations for recognition of motion events involving any number of entities.