The Bactra Review   Emergence
Let us lapse into mathematical logic --- Holland doesn't, but I doubt these parts of his book can be followed easily by anyone who can't make the silent mental adjustments into notation. We have a relation R among a class of terms A, and we write R(a, b) if the relation holds between a and b. (This is of a piece with the usual definition of a relation as a class of ordered pairs. Note that R(a, b) is not the same as R(b, a), unless a=b.) We can model R by another relation Q, between a different class of terms M, if there is an invertible function S from A to M such that R(a,b) iff Q(S(a), S(b)); as Russell would say, R and Q have the same relation-number. (This is easily extended to non-binary relations.) A model for Holland is thus essentially the same as a "representation" for Russell in "Vagueness," and rather like an "interpretation" for Sperber and Wilson in Relevance. Holland is primarily concerned with models of processes, where the relevant relation is causation, or, if you prefer, succession.