On some families of formal languages obtained by regulated derivations
Arto K. Salomaa · Annales Academiae Scientiarum Fennicae Series A I Mathematica · 1971
A. I. 4ig (1) :{(L,z,I) -q, $,2,o) and that every language in this family is recursive.ft remains an open problem whether or not the farnily occurring in (1) contains properl5r the family of context-sensitive languages.fn Section 4, we investigate the family (2) =t1z,e,o) obtained using context-free core productions (including productions rvith the empty word on the right side) with a regular control language under non-checking interpretation.An operation characteristic for this family is introduced and its properties studied.A result, concerning a subfamily of (2) is obtained.ft is known, [6], [7], that if in (2) 0 is replaced by I, the resulting family equals s41O;.However, the size of the family (2)remains an open problem.