Acta Cybernetica
Jewels are Forever, Contributions on Theoretical Computer Science in Honor of Arto Salomaa
Typechecking for XML transformers
Journal of Computer and System Sciences - Special issue on PODS 2000
Tree-walking automata do not recognize all regular languages
Proceedings of the thirty-seventh annual ACM symposium on Theory of computing
Tree-walking automata cannot be determinized
Theoretical Computer Science - Automata, languages and programming: Logic and semantics (ICALP-B 2004)
Complementing deterministic tree-walking automata
Information Processing Letters
Nested pebbles and transitive closure
STACS'06 Proceedings of the 23rd Annual conference on Theoretical Aspects of Computer Science
XML transformation by tree-walking transducers with invisible pebbles
Proceedings of the twenty-sixth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
XPath, transitive closure logic, and nested tree walking automata
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Language and Automata Theory and Applications
Information Processing Letters
Pebble alternating tree-walking automata and their recognizing power
Acta Cybernetica
Pebble Macro Tree Transducers with Strong Pebble Handling
Fundamenta Informaticae
Transitive closure logic, nested tree walking automata, and XPath
Journal of the ACM (JACM)
On pebble automata for data languages with decidable emptiness problem
Journal of Computer and System Sciences
Pebble weighted automata and transitive closure logics
ICALP'10 Proceedings of the 37th international colloquium conference on Automata, languages and programming: Part II
Foundations of XML based on logic and automata: a snapshot
FoIKS'12 Proceedings of the 7th international conference on Foundations of Information and Knowledge Systems
Pebble Macro Tree Transducers with Strong Pebble Handling
Fundamenta Informaticae
Complexity of pebble tree-walking automata
FCT'07 Proceedings of the 16th international conference on Fundamentals of Computation Theory
Adding pebbles to weighted automata
CIAA'12 Proceedings of the 17th international conference on Implementation and Application of Automata
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Two variants of pebble tree-walking automata on binary trees are considered that were introduced in the literature. It is shown that for each number of pebbles, the two models have the same expressive power both in the deterministic case and in the nondeterministic case. Furthermore, nondeterministic (resp. deterministic) tree-walking automata with n + 1 pebbles can recognize more languages than those with n pebbles. Moreover, there is a regular tree language that is not recognized by any tree-walking automaton with pebbles. As a consequence, FO+posTC is strictly included in MSO over trees.