 Primiero (2020) proposes a definition of implementation not as a relation between two fixed levels, but one that is allowed to range over any LoA. Under this view, an implementation I is a relation of instantiation holding between a LoA and any other one higher in the abstraction hierarchy. Accordingly, a physical computing machine is an implementation of assembly/machine code operations; by transitivity, it can also be considered as an instantiation of a set of instructions expressed in high-level programming language instructions. A program expressed in a high-level language is an implementation of an algorithm; but it can also be taken to be the instantiation of a set of specifications.