An Inverse Homomorphic Characterization of Full Principal AFL

Abstract

The main result of this paper is: Let L be a full principal AFL closed under context-free substitution. Then there is a fixed language l 0 in L such that for each L in L there exist a weak coding h and a homomorphism g such that L = hg −1( L 0). As a corollary, it immediately follows that there is a fixed ETOL language L 0 such that for each ETOL language L there exist a weak coding h and a homomorphism g such that L = hg −1( L 0).