descriptional systems in an abstract fashion. We aim at categorizing

non-recursive trade-offs by bounds on their growth rate, and show

how to deduce such bounds in general. We also identify criteria

which, in the spirit of abstract language theory, allow us to deduce

non-recursive tradeoffs from effective closure properties of

language families on the one hand, and differences in the

decidability status of basic decision problems on the other. We

develop a qualitative classification of non-recursive trade-offs in

order to obtain a better understanding of this very fundamental

behaviour of descriptional systems