%A J. Casti %T On the theory of models and the modelling of natural phenomena. %X It is argued that a modelling relation in an encoding of a set of physical observables, characterising a natural system N, into an appropriate formal mathematical structure. The theorems of the formal structure are then decoded into true statements about N. Various system-theoretic concepts such as bifurcation, similarity, system analogy, reductionism, and complexity are then seen to be naturally expressed. %P 73-92 %B On the theory of models and the modelling of natural phenomena. %E G. Bahrenberg %E M. Fischer %E P. Nijkamp %D 1984 %I Gower %L iiasa13686