Handbook of formal languages, vol. 1
Handbook of formal languages, vol. 3
On the state complexity of k-entry deterministic finite automata
Journal of Automata, Languages and Combinatorics - Special issue: selected papers of the second internaional workshop on Descriptional Complexity of Automata, Grammars and Related Structures (London, Ontario, Canada, July 27-29, 2000)
Journal of Computer and System Sciences
On the minimization of XML Schemas and tree automata for unranked trees
Journal of Computer and System Sciences
A Second Course in Formal Languages and Automata Theory
A Second Course in Formal Languages and Automata Theory
Descriptional and Computational Complexity of Finite Automata
LATA '09 Proceedings of the 3rd International Conference on Language and Automata Theory and Applications
Operational state complexity of nested word automata
Theoretical Computer Science
Descriptional complexity of unambiguous nested word automata
LATA'11 Proceedings of the 5th international conference on Language and automata theory and applications
Deterministic automata on unranked trees
FCT'05 Proceedings of the 15th international conference on Fundamentals of Computation Theory
State complexity of the concatenation of regular tree languages
Theoretical Computer Science
State complexity of kleene-star operations on trees
WTCS'12 Proceedings of the 2012 international conference on Theoretical Computer Science: computation, physics and beyond
Transformations Between Different Models of Unranked Bottom-Up Tree Automata
Fundamenta Informaticae
State complexity of projection and quotient on unranked trees
DCFS'12 Proceedings of the 14th international conference on Descriptional Complexity of Formal Systems
Lower bounds for the size of deterministic unranked tree automata
Theoretical Computer Science
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A common definition of tree automata operating on unranked trees uses a set of vertical states that define the bottom-up computation, and the transitions on vertical states are determined by so called horizontal languages recognized by finite automata on strings. It is known that, in this model, a deterministic tree automaton with the smallest total number of states (that is, vertical states and states used for automata to define the horizontal languages) does not need to be unique nor have the smallest possible number of vertical states. We consider the question by how much we can reduce the total number states by introducing additional vertical states. We give an upper bound for the state trade-off for deterministic tree automata where the horizontal languages are defined by DFAs (deterministic finite automata). Also, we give a lower bound construction that reduces the number of horizontal states, roughly, from 4n to 8n by doubling the number of vertical states. The lower bound is close to the worst-case upper bound in the case where the number of vertical states is multiplied by a constant. We show that deterministic tree automata where the horizontal languages are specified by NFAs (nondeterministic finite automata) can have no trade-offs between the numbers of vertical states and horizontal states, respectively. We study corresponding trade-offs also for nondeterministic tree automata.