Definition: An extension of a finite state machine that operates on n-ary constructors. Where a finite state automaton reaches a new state with a single state and character, a tree automaton takes n states and constructors. Tree automata may be top-down (starting from the root) or bottom-up (starting from the leaves), and deterministic or nondeterministic.
See also deterministic finite tree automaton, nondeterministic finite tree automaton, deterministic tree automaton, nondeterministic tree automaton, bottom-up tree automaton, top-down tree automaton.
Note: Words for finite state automata can be seen as composed of unary constructors, the alphabet, and a 0-ary constructor, the end of the word.
Nondeterministic top-down and bottom-up automata, and deterministic bottom-up automata are equivalent, but top-down automata are weaker.
Tree Automata Techniques and Applications page.
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Entry modified 22 October 2007.
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Cite this as:
David Monniaux, "tree automaton", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 22 October 2007. (accessed TODAY) Available from: http://www.nist.gov/dads/HTML/treeAutomaton.html