DECOMPOSITION OF WEIGHTED MULTIOPERATOR TREE AUTOMATA

2009 ◽  
Vol 20 (02) ◽  
pp. 221-245 ◽  
Author(s):  
TORSTEN STÜBER ◽  
HEIKO VOGLER ◽  
ZOLTÁN FÜLÖP
Keyword(s):  
Tree Automata ◽  
Commutative Monoid ◽  
Weighted Tree ◽  
Tree Language ◽  
Bottom Up ◽  
Tree Series ◽  
Finite State ◽  
Tree Languages ◽  
Tree Transformation

Weighted multioperator tree automata (for short: wmta) are finite-state bottom-up tree automata in which the transitions are weighted with an operation taken from some multioperator monoid. A wmta recognizes a tree series which is a mapping from the set of trees to some commutative monoid. We prove that every wmta recognizable tree series can be decomposed into a relabeling tree transformation, a recognizable tree language, and a tree series computed by a homomorphism wmta; vice versa, the composition of an arbitrary relabeling tree transformation, a recognizable tree language, and a tree series computed by a homomorphism wmta yields a wmta recognizable tree series. We use this characterization result for specific multioperator monoids and prove (1) a new decomposition of polynomial bottom-up tree series transducers over semirings and (2) a new characterization of tree series which are recognizable by weighted tree automata over semirings, in terms of projections of local tree languages.

RELATING TREE SERIES TRANSDUCERS AND WEIGHTED TREE AUTOMATA

2005 ◽  
Vol 16 (04) ◽  
pp. 723-741 ◽  
Author(s):  
ANDREAS MALETTI
Keyword(s):  
Tree Automata ◽  
Formal Representation ◽  
Weighted Tree ◽  
Bottom Up ◽  
Operation Symbol ◽  
Tree Series ◽  
Pumping Lemma ◽  
Emptiness Problem ◽  
Weighted Tree Automata ◽  
The Given

Bottom-up tree series transducers (tst) over the semiring [Formula: see text] are implemented with the help of bottom-up weighted tree automata (wta) over an extension of [Formula: see text]. Therefore bottom-up [Formula: see text]-weighted tree automata ([Formula: see text]-wta) with [Formula: see text] a distributive Ω-algebra are introduced. A [Formula: see text]-wta is essentially a wta but uses as transition weight an operation symbol of the Ω-algebra [Formula: see text] instead of a semiring element. The given tst is implemented with the help of a [Formula: see text]-wta, essentially showing that [Formula: see text]-wta are a joint generalization of tst (using IO-substitution) and wta. Then a semiring and a wta are constructed such that the wta computes a formal representation of the semantics of the [Formula: see text]-wta. The applicability of the obtained presentation result is demonstrated by deriving a pumping lemma for deterministic finite [Formula: see text]-wta from a known pumping lemma for deterministic finite wta. Finally, it is observed that the known decidability results for emptiness cannot be applied to obtain decidability of emptiness for finite [Formula: see text]-wta. Thus with help of a weaker version of the derived pumping lemma, decidability of the emptiness problem for finite [Formula: see text]-wta is shown under mild conditions on [Formula: see text].

HYPER-MINIMIZATION FOR DETERMINISTIC TREE AUTOMATA

2013 ◽  
Vol 24 (06) ◽  
pp. 815-830 ◽  
Author(s):  
ARTUR JEŻ ◽  
ANDREAS MALETTI
Keyword(s):  
Finite Difference ◽  
Minimization Problem ◽  
Fast Algorithms ◽  
Input Tree ◽  
Tree Automaton ◽  
Tree Automata ◽  
Compression Technique ◽  
Bottom Up ◽  
Finite State ◽  
Transition Table

Hyper-minimization is a recent automaton compression technique that can reduce the size of an automaton beyond the limits imposed by classical minimization. The additional compression power is enabled by allowing a finite difference in the represented language. The necessary theory for hyper-minimization is developed for (bottom-up) deterministic tree automata. The hyper-minimization problem for deterministic tree automata is reduced to the hyper-minimization problem for deterministic finite-state string automata, for which fast algorithms exist. The fastest algorithm obtained in this way runs in time [Formula: see text], where m is the size of the transition table and n is the number of states of the input tree automaton.

scholarly journals Crisp-determinization of weighted tree automata over strong bimonoids

2021 ◽  
Vol vol. 23 no. 1 (Automata, Logic and Semantics) ◽  
Author(s):  
Zoltán Fülöp ◽  
Dávid Kószó ◽  
Heiko Vogler
Keyword(s):  
Finite Order ◽  
Positive Answer ◽  
Order Property ◽  
Sufficient Condition ◽  
Tree Automata ◽  
Weighted Tree ◽  
Bottom Up ◽  
Initial Algebra ◽  
Initial Algebra Semantics ◽  
Weighted Tree Automata

We consider weighted tree automata (wta) over strong bimonoids and their initial algebra semantics and their run semantics. There are wta for which these semantics are different; however, for bottom-up deterministic wta and for wta over semirings, the difference vanishes. A wta is crisp-deterministic if it is bottom-up deterministic and each transition is weighted by one of the unit elements of the strong bimonoid. We prove that the class of weighted tree languages recognized by crisp-deterministic wta is the same as the class of recognizable step mappings. Moreover, we investigate the following two crisp-determinization problems: for a given wta ${\cal A}$, (a) does there exist a crisp-deterministic wta which computes the initial algebra semantics of ${\cal A}$ and (b) does there exist a crisp-deterministic wta which computes the run semantics of ${\cal A}$? We show that the finiteness of the Nerode algebra ${\cal N}({\cal A})$ of ${\cal A}$ implies a positive answer for (a), and that the finite order property of ${\cal A}$ implies a positive answer for (b). We show a sufficient condition which guarantees the finiteness of ${\cal N}({\cal A})$ and a sufficient condition which guarantees the finite order property of ${\cal A}$. Also, we provide an algorithm for the construction of the crisp-deterministic wta according to (a) if ${\cal N}({\cal A})$ is finite, and similarly for (b) if ${\cal A}$ has finite order property. We prove that it is undecidable whether an arbitrary wta ${\cal A}$ is crisp-determinizable. We also prove that both, the finiteness of ${\cal N}({\cal A})$ and the finite order property of ${\cal A}$ are undecidable.

Operational State Complexity of Subtree-Free Regular Tree Languages

2016 ◽  
Vol 27 (06) ◽  
pp. 705-724
Author(s):  
Sang-Ki Ko ◽  
Hae-Sung Eom ◽  
Yo-Sub Han
Keyword(s):  
The State ◽  
Tree Automaton ◽  
Top Down ◽  
Tree Language ◽  
Worst Case ◽  
Bottom Up ◽  
State Complexity ◽  
Regular Tree ◽  
Tree Languages

We introduce subtree-free regular tree languages that are closely related to XML schemas and investigate the state complexity of basic operations on subtree-free regular tree languages. The state complexity of an operation for regular tree languages is the number of states that are sufficient and necessary in the worst-case for the minimal deterministic ranked tree automaton that accepts the tree language obtained from the operation. We establish the precise state complexity of (sequential, parallel) concatenation, (bottom-up, top-down) star, intersection and union for subtree-free regular tree languages.

scholarly journals Surface Tree Languages and Parallel Derivation Trees

1975 ◽  
Vol 4 (44) ◽  
Author(s):  
Joost Engelfriet
Keyword(s):  
State Transformation ◽  
Top Down ◽  
Finite State ◽  
Tree Languages ◽  
Tree Transformation

The surface tree languages obtained by top-down finite state transformation of monadic trees are exactly the frontier-preserving homomorphic images of sets of derivation trees of ETOL systems. The corresponding class of tree transformation languages is therefore equal to the class of ETOL languages.

scholarly journals Formal Tree Series

2002 ◽  
Vol 9 (21) ◽  
Author(s):  
Zoltán Ésik ◽  
Werner Kuich
Keyword(s):  
Fixed Point Theory ◽  
Point Theory ◽  
Point Of View ◽  
Tree Automata ◽  
Survey Paper ◽  
Tree Series ◽  
Algebraic Treatment ◽  
Tree Languages ◽  
Formal Power ◽  
Kleene Theorem

In this survey we generalize some results on formal tree languages, tree grammars and tree automata by an algebraic treatment using semirings, fixed point theory, formal tree series and matrices. The use of these mathematical constructs makes definitions, constructions, and proofs more satisfactory from an mathematical point of view than the customary ones. The contents of this survey paper is indicated by the titles of the sections:<dl compact="compact"><dt>1.</dt><dd>Introduction</dd><dt>2.</dt><dd>Preliminaries</dd><dt>3.</dt><dd>Tree automata and systems of equations</dd><dt>4.</dt><dd>Closure properties and a Kleene Theorem for recognizable tree series</dd><dt>5.</dt><dd>Pushdown tree automata, algebraic tree systems, and a Kleene Theorem</dd><dt>6.</dt><dd>Tree series transducers</dd><dt>7.</dt><dd>Full abstract families of tree series</dd><dt>8.</dt><dd>Connections to formal power series</dd></dl>

A Characterization of Irreducible Sets Modulo Left-Linear Term Rewriting Systems by Tree Automata

1990 ◽  
Vol 13 (2) ◽  
pp. 211-226
Author(s):  
Z. Fülop ◽  
S. Vágvölgyi
Keyword(s):  
Term Rewriting ◽  
Linear Term ◽  
Tree Automata ◽  
Top Down ◽  
Term Rewriting Systems ◽  
Tree Language ◽  
Rewriting Systems ◽  
Term Rewriting System ◽  
Look Ahead

The concept of top-down tree automata with prefix look-ahead is introduced. It is shown that a tree language is the set of irreducible trees of a left-linear term rewriting system if and only if it can be recognized by a one-state deterministic top-down tree automaton with pre fix look-ahead.

scholarly journals ALGEBRAIC CHARACTERIZATION OF LOGICALLY DEFINED TREE LANGUAGES

2010 ◽  
Vol 20 (02) ◽  
pp. 195-239 ◽  
Author(s):  
ZOLTÁN ÉSIK ◽  
PASCAL WEIL
Keyword(s):  
Algebraic Structure ◽  
Algebraic Characterization ◽  
Tree Language ◽  
Regular Tree ◽  
First Order ◽  
Product Operation ◽  
Finite Word ◽  
Tree Languages ◽  
Block Product

We give an algebraic characterization of the tree languages that are defined by logical formulas using certain Lindström quantifiers. An important instance of our result concerns first-order definable tree languages. Our characterization relies on the usage of preclones, an algebraic structure introduced by the authors in a previous paper, and of the block product operation on preclones. Our results generalize analogous results on finite word languages, but it must be noted that, as they stand, they do not yield an algorithm to decide whether a given regular tree language is first-order definable.

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