Rent’s rule and related concepts of connectivity such as dimensionality, line-length distributions, and separators have found great use in fundamental studies of different interconnection media, including superconductors and optics, as well as the study of optoelectronic computing systems. In this paper generalizations for systems for which the Rent exponent is not constant throughout the interconnection hierarchy are provided. The origin of Rent’s rule is stressed as resulting from the embedding of a high-dimensional information flow graph to two- or three-dimensional physical space. The applicability of these traditionally solid-wire-based concepts to free-space optically interconnected systems is discussed.