Formalisms and axiomatic theories are designed to support reasoning, they are often intended with a preferred interpretation and a targeted ontology. Questions of proper interpretations and of the possible challenge of an intended interpretation arise when integrating a particular theory in pre-existing formal and ontological settings. This paper reports on an instance of this general problem of ontological engineering. The case study is that of the integration of the Region Connection Calculus

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... for spatial reasoning in the Cyc knowledge base. We show that given the assumptions on the Cyc ontology, RCC had to be interpreted within a substantivalist metaphysic of space as a Boolean algebra of spatial regions which are distinct from their occupants. The RCC literature suggests such an intended interpretation, and this paper intends to show that this was a necessary condition of integration in Cyc's ontology. This led to the enrichment of the Cyc knowledge base, rather than to a radical modification of the upper-level ontology.