Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Composition Closure of Linear Extended Top-down Tree Transducers   Linear extended top-down tree transducers (or synchronous tree-substitution
grammars) are popular formal models of tree transformations. The expressive
power of compositions of such transducers with and without regular look-ahead
is investigated. In particular, the restrictions of nondeletion,
epsilon-freeness, and strictness are considered. The composition hierarchy
turns out to be finite for all epsilon-free (all rules consume input) variants
of these transducers except for nondeleting epsilon-free linear extended
top-down tree transducers. The least number of transducers needed for the full
expressive power of arbitrary compositions is presented. In all remaining cases
(including nondeleting epsilon-free linear extended top-down tree transducers)
the composition hierarchy does not collapse.

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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: cond-mat
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The categories of this paper are: solv-int
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat