ABSTRACT
To this point, we have discussed only the nature of software systems. All of our representations were for abstract machines: an operational machine, a functional machine, and a language machine. The users of our software systems will reside in a very different tangible physical universe. Users cannot interact with our software directly. They can only do so through some hardware artifact that we will create (or find). What this means is that user manipulation of the operational environment must occur through the manipulation of some physical artifact. This artifact will serve as an interface to the abstract machine.
