Boundary NLC graph grammars--basic definitions, normal forms, and complexity
Information and Control
Formal languages
Apex graph grammars and attribute grammars
Acta Informatica
Boundary graph grammars with dynamic edge relabeling
Journal of Computer and System Sciences
An elementary proof of double Greibach normal form
Information Processing Letters
Node replacement graph languages squeezed with chains, trees, and forests
Information and Computation
Context-free languages and pushdown automata
Handbook of formal languages, vol. 1
A hierarchy of eNCE families of graph languages
Theoretical Computer Science
Double Greibach operator grammars
Theoretical Computer Science
L(A) = L(B)? decidability results from complete formal systems
Theoretical Computer Science
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
Introduction to Formal Language Theory
Introduction to Formal Language Theory
| Hi-index | 5.23 |
A pushdown automaton (PDA) is quasi-rocking if it preserves the stack height for no more than a bounded number of consecutive moves. Every PDA can be transformed into an equivalent one that is quasi-rocking and real-time and every finite-turn (one-turn) PDA can be transformed into an equivalent one that is quasi-rocking or real-time. The quasi-rocking [quasi-rocking in the increasing mode, and quasi-rocking in the decreasing mode] real-time restriction in finite-turn (one-turn) PDAs coincides with the double Greibach [reverse Greibach, and Greibach] form in nonterminal-bounded (linear) context-free grammars. This provides complete grammatical characterizations of quasi-rocking and/or real-time (finite-turn and one-turn) PDAs and, together with known relations and other relations proved in the present paper, yields an extended hierarchy of PDA languages. Basic decision properties for PDAs can be stated in stronger forms by using the quasi-rocking and real-time restrictions and their undecidability/decidability status rests on the way PDAs quasi-rock.