Handbook of formal languages, vol. 3
The Simulation of Two-Dimensional One-Marker Automata by Three-Way Turing Machines
Proceedings of the 5th International Meeting of Young Computer Scientists on Machines, Languages, and Complexity
New Results on Alternating and Non-deterministic Two-Dimensional Finite-State Automata
STACS '01 Proceedings of the 18th Annual Symposium on Theoretical Aspects of Computer Science
A note on one-pebble two-dimensional Turing machines
Information Sciences: an International Journal
Automata on a 2-dimensional tape
FOCS '67 Proceedings of the 8th Annual Symposium on Switching and Automata Theory (SWAT 1967)
Complexity of multi-head finite automata: Origins and directions
Theoretical Computer Science
Graph Algorithms
Two-dimensional sgraffito automata
DLT'12 Proceedings of the 16th international conference on Developments in Language Theory
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We compare two types of automata for accepting picture languages to each other: the two-dimensional one-marker automaton and the sgraffito automaton. On the one hand, it is shown that deterministic sgraffito automata are strictly more powerful than deterministic two-dimensional one-marker automata. On the other hand, nondeterministic two-dimensional one-marker automata accept some picture languages that cannot be accepted by sgraffito automata. However, if nondeterministic two-dimensional one-marker automata were to accept all picture languages that are accepted by (deterministic) sgraffito automata, then the complexity classes NL (nondeterministic logarithmic space) and P (deterministic polynomial time) would coincide. Accordingly, it is likely that the classes of picture languages accepted by these two types of nondeterministic automata are incomparable under inclusion.