AbstractIn this paper we discuss how metaphors, and in general the translation of meaning between different knowledge domains, relate to the understanding of the interface between a human and a computing system, hence to its naturalness. Focusing on tangible user interfaces we analyze metaphors, analogies and symbolic representations developed in the computing interaction area to represent concepts in human computer interfaces along three main dimensions: the coherence of their use in linking concepts of some domain to the implementation of the interface, the coverage of the concepts implemented with respect to the amplitude of the knowledge domain, and their compliance with respect to the expectations of the human experience. We justify th...