Physical and Computational Description

Abstract This chapter examines physical and computational descriptions and their respective targets. It introduces the elements of physical description and a classification of physical descriptions by their granularity, specificity, and completeness. Depending on their level of granularity, physical descriptions may be microscopic or macroscopic. Depending on their degree of specificity, physical descriptions may be structural or constitutive. Finally, physical descriptions may be complete or partial. The chapter similarly introduces the elements of formal definitions of computations and highlights similarities and differences between physical and computational descriptions in preparation for their hybridization in physical-computational descriptions of physical computing systems. The key difference is that a physical system may possess features not captured by some of its physical descriptions, whereas a formally defined computing system is completely specified by its formal computational description.