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Adpositional Grammars. A multilingual grammar formalism for NLP.

In the field of computational linguistics, the representation of natural languages (NL) in formal grammar terms is a well-known issue and a wicked problem indeed. In fact, some formal grammars lack of lexical and semantic information representation, reducing the linguistic structure to syntax.
On the other side, approaches like dependency grammars lose expressive power, under a computational point of view. Adpositional grammars (adgrams) are a novel grammar formalism that overcomes these limitations. Adgrams are based on Pennacchietti’s research, who put together Brøndal’s logic description of prepositions, Tesnerian notion of valence, Langacker ’s cognitive dichotomy trajector/landmark and Silvio Ceccato’s pioneer work in the field on machine translation (MT). The result is a quasi-formal description of adpositions, being the junctors of language structure. This description is called adpositional space. Each adpositional space is made of
four adpositional types: Plus (⊕), Minus (⊖), Slash (⊘), Times (⊗). The resulting structure is cognitively sound and formally inspiring, as adpositional trees (adtrees) can be built as special Porphyrian trees, going beyond the Tesnerian somehow fuzzy concept of dependency.
This dissertation puts Pennacchietti’s work a step forward. In fact, here adgrams consider the ultimate unit of NLs being the morpheme, not the word, and therefore they offer a coherent theory of both morphology and syntax. Hence, the collocation phenomena are considered like zero morphemes. Moreover, a sharp distinction in the dictionary between the adpositional space, essentially made of closed morphemes, and the lexicon, made of open morphemes. Moving again from Tesnerian structural syntax, open morphemes always have a fundamental grammar character: stative (O), adjunctive (A, as stative modifiers), and verbal (I), circumstantial (E, as verbal modifiers). The Tesnierian approach is validated through Whorf ’s
research results comparing grammars of typologically distant NLs.

The second part shows that adgrams are computable, as they can be implemented with a strong, robust formalism. A concrete instance of the formal model of adgrams is given through the quasi-natural language Esperanto (QNL, Lyons), showing the linguistic viability of the model. The
formal model should be used appropriately in an ad hoc epistemological scenario, called ‘the translation game’, designed as a Gedankenexperiment à la Turing. A toy example is also given. In the third part the implementation is explained with all its details: the implementation of Esperanto is made in exactly 179 logic formulas, 56 of which are predicates. The formal model is promising to be generalised for any NLs, and how to do this was explained in various points of the third part. Finally, this dissertation shows that adgrams are a powerful NL grammar formalism which is at the
same time cross-linguistic, cognitively grounded and formally robust and computationally sound.

Mostra/Nascondi contenuto.
Chapter 1 Introduction How are the laws of human thought made? How can linguistic knowledge be formalised? These two questions were posed as two sides of the same coin first by Gottfried Wilhelm Leibniz in the 17th century. His answer to the first question was the characteristica universalis. Af- ter him, improvements were achieved by many others, among them George Boole with his calculus of logic, Gottlob Frege with his Begriffsschrift, Giu- seppe Peano with his axiomatisation of arithmetics, not to mention Kurt Go¨del’s theorem and the Church-Turing thesis, which is eventually the foundation of Computer Science.1 In order to answer the second question, Leibniz proposed the lingua generalis.2 After him, this research path was also followed by Ludwik Lejzer Zamenhof Esperanto and again by Giuseppe Peano with his Latino sine Flexione. Zamenhof succeeded where Peano failed, i.e., to build a sta- ble speech community for the newborn language. As a scientific object of study, Esperanto indirectly influenced linguistics since its very begin- ning. In fact, the mathematician Rene´ de Saussure was also a pioneer of Esperantology, – i.e., the linguistic analysis of Esperanto – deeply influ- encing his brother Ferdinand, exactly during the years of his conception of linguistics and structuralism as sciences.3 After Ferdinand de Saussure, improvements were achieved by Noam Chomsky’s generative grammars and Lucien Tesnie`re’s syntaxe structurale.4 Peano’s life and work, as well as Chomsky-Schu¨tzenberger’s hierarchy of formal grammars, both demonstrate that the intuition of Leibniz was correct – i.e., that these two questions are intertwined one with the other. Standing on the shoulders of giants, the aim of this dissertation is to take a step forward in this direction, which will be hopefully made by using the specific tool of adpositional grammars. 21

Tesi di Dottorato

Dipartimento: DICOM

Autore: Federico Gobbo Contatta »

Composta da 375 pagine.

 

Questa tesi ha raggiunto 231 click dal 22/09/2009.

 

Consultata integralmente una volta.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.