demanded of system-theoretic
interpretations.  This account is tantamount to the other side of the ledger,
the &quot;model-theoretic&quot; aspect of a symbol system, at least in so far as the
present discussion has dealt with it.

More is required of the modeler, however, in order to find the desired
kinds of system-theoretic models, for example, state transition systems,
and this brings the search for realizations of formal systems down to the
tougher part of the exercise.  Some of the problems that emerge