Composition Closure of Linear Extended Top-down Tree Transducers
نویسندگان
چکیده
منابع مشابه
Composition Closure of ε-Free Linear Extended Top-Down Tree Transducers
The expressive power of compositions of linear extended topdown tree transducers with and without regular look-ahead is investigated. In particular, the restrictions of ε-freeness, strictness, and nondeletion are considered. The composition hierarchy is finite for all ε-free variants of these transducers except for ε-free nondeleting linear extended top-down tree transducers. The least number o...
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In this survey (functional) compositions of weighted tree transformations computable by weighted extended top-down tree transducers are investigated. The existing results in the literature are explained and illustrated. It is argued, why certain compositions are not possible in the general case, and 3 informed conjectures provide an insight into potentially 3 new composition results that extend...
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Unfortunately, the class of transformations computed by linear extended top-down tree transducers with regular look-ahead is not closed under composition. It is shown that the class of transformations computed by certain linear bimorphisms coincides with the previously mentioned class. Moreover, it is demonstrated that every linear epsilon-free extended top-down tree transducer with regular loo...
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A composition procedure for linear and nondeleting extended top-down tree transducers is presented. It is demonstrated that the new procedure is more widely applicable than the existing methods. In general, the result of the composition is an extended top-down tree transducer that is no longer linear or nondeleting, but in a number of cases these properties can easily be recovered by a post-pro...
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Many aspects of machine translation of natural languages can be formalized by employing weighted finite-state (string) transducers [22, 40]. Successful implementations based on this wordor phrasebased approach are, for example, the At&t Fsm toolkit [41], Xerox’s finite-state calculus [24], the Rwth toolkit [23], Carmel [19], and OpenFst [2]. However, the phrase-based approach is not expressive ...
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ژورنال
عنوان ژورنال: Theory of Computing Systems
سال: 2015
ISSN: 1432-4350,1433-0490
DOI: 10.1007/s00224-015-9660-2