This paper is mainly concerned with the relation-algebraic aspects of the well-known Region Connection Calculus (RCC).It is shown that the complemented closed disk algebra is a representation for the relation algebra determined by the RCC11 table,which was first described by Düntsch.The domain of this algebra contains two classes of regions,the closed disks and closures of their complements in the real plane,and the contact relation is the standard Whiteheadean contact(i.e.aCb iff a∩b≠? .