Using Thèrcc' Formalism to Describe the Topology of Spherical Regions 1

1 The support of the EPSRC under grant no. GR/H 78955, and helpful comments from Tony Cohn, are gratefully acknowledged. Abstract This research report concerns the topology of 2-dimensional regions embedded in spherical surfaces, such as that of the Earth (`spherical regions'). It shows that the RCC (Region-Connection Calculus) rst-order logic formalism for qualitative spatial representation and reasoning is suuciently expressive to support a rich topological taxonomy of uniformly two-dimensional regions forming parts of a spherical surface such as the Earth's. However, there are potentially useful constraints on the topology of such regions which the language of RCC cannot capture. Furthermore, the spherical model of the RCC axiom set developed here permits the construction of a proof that the theory axiomatised by this axiom set is undecidable (a result also derivable from (Grzegorczyk 1951).