Derivation languages of grammar forms†
Hermann A. Maurer, A. Salomaa, D. Wood · International Journal of Computer Mathematics · 1981
The family of derivation languages or Szilard languages associated with a grammar form is studied. It is shown that Szilard equivalence, regular completeness and regular sufficiency are decidable properties. Although the decidability of left Szilard equivalence remains open, we reduce this problem to the equivalence problem for a special class of s-grammar forms