  This paper is mainly concerned with the relation-algebraical aspects of the
well-known Region Connection Calculus (RCC). We show that the contact relation
algebra (CRA) of certain RCC model is not atomic complete and hence infinite.
So in general an extensional composition table for the RCC cannot be obtained
by simply refining the RCC8 relations. After having shown that each RCC model
is a consistent model of the RCC11 CT, we give an exhaustive investigation
about extensional interpretation of the RCC11 CT. More important, we show the
complemented closed disk algebra is a representation for the relation algebra
determined by the RCC11 table. The domain of this algebra contains two classes
of regions, the closed disks and closures of their complements in the real
plane.
