16.380, Diss: Cognitive Science/Comp Ling: Chesi: 'Phases ...'

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LINGUIST List: Vol-16-380. Tue Feb 08 2005. ISSN: 1068 - 4875.

Subject: 16.380, Diss: Cognitive Science/Comp Ling: Chesi: 'Phases ...'

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1)
Date: 08-Feb-2005
From: Cristiano Chesi < chesi at media.unisi.it >
Subject: Phases and Cartography in Linguistic Computation: Toward a Cognitively Motivated Computational Model of Linguistic Competence

	
-------------------------Message 1 ----------------------------------
Date: Tue, 08 Feb 2005 12:16:09
From: Cristiano Chesi < chesi at media.unisi.it >
Subject: Phases and Cartography in Linguistic Computation: Toward a Cognitively Motivated Computational Model of Linguistic Competence


Institution: University of Siena
Program: Ph.D. in Cognitive Science
Dissertation Status: Completed
Degree Date: 2004

Author: Cristiano Chesi

Dissertation Title: Phases and Cartography in Linguistic Computation: Toward a
Cognitively Motivated Computational Model of Linguistic Competence

Dissertation URL:  http://www.ciscl.unisi.it/doc/doc_pub/chesi04-thesis.pdf

Linguistic Field(s): Cognitive Science
                     Computational Linguistics
                     Syntax


Dissertation Director(s):
Robert C Berwick
Marco Gori
Luigi Rizzi

Dissertation Abstract:

In this thesis I define and evaluate from a cognitive perspective some
fundamental properties of a computational model of linguistic competence
that aims to be descriptively/explanatorily adequate, flexible (effectively
usable in performance tasks such as parsing and generation) and realistic
(tractable in computational terms and reasonable with respect to human
performance data).

With the purpose of doing that, in the first chapter of this dissertation I
introduce the linguistic concepts that are used in most frameworks, seeking
to highlight their cognitive nature (essentially comparing processing at
other cognitive levels, such as vision); in particular, consideration will
be given to defining what features are, how they combine and which
relations shall be defined among them; additionally some essential concepts
will be provided in order to understand cost functions (complexity metrics)
of the proposed devices.

Generative frameworks will be systematically reviewed in the first part of
chapter 2 (Principle and Parameters / Extended Standard Theory, the
Minimalist Program and a 'unusual' processing perspective for this
framework, that is Phillip's (1996) left-to-right processing model; finally
the Cartographical Approach will be explored). The second part of this
chapter will show some (partially successful) attempts to
implement/formalize these linguistic frameworks (the Principle-based
parsing approach, Stabler's minimalist grammar formalization, and Fong's
minimalist parser).

The rest of the thesis will try to solve many standing problematic issues:
in order to provide a precise context, in chapter 3 I will firstly
formalize the idea of structural description then the (performance) tasks
that must access the grammar (essentially parsing and generation, which are
specific cases of comprehension and production respectively). Afterwards,
the most problematic aspects of the language (ambiguities and long distance
dependencies) will be formalized with respect to the proposed performance
tasks. Finally the formalization of a minimalist grammar (inspired by
Stabler's 1997 work and the Minimalist Program) enriched with
considerations on the articulate geometry of the functional feature
structures proposed within the Cartographic Approach will be provided.

>From the theoretical perspective, the standard minimalist approach sketches
a model that does not fit in a clear way with specific performance
algorithms such as parsing or generation even though much emphasis is put
on 'interface properties'. The grammar formalized considers some important
constraints posed both by the generation and parsing problems, in the end
defining a model that is:

- usable both in parsing and in generation;
- cognitively motivated;
- tractable;
- as much as possible deterministic.

To achieve these results I focus on three properties that are not only
cognitively plausible, but also formally and computationally advantageous:

- structure building operations can be embedded within the grammar if they
apply either top-down (in generation) or from-left-to-right (in parsing);
- using a Linearization Principle (inspired by Kayne's 1994 LCA) and fixing
the functional structure by mean of a universal hierarchy (Cartographic
Approach) makes the algorithm mostly deterministic;
- formalizing phases (cf. Chomsky 1999) helps us to make the algorithm (in
relation to dealing with ambiguities and long distance relations) tractable.

The last chapter, chapter 4, will provide a specification of
thealgorithm/grammar used, showing which empirical coverage this model can
reach. In particular cases of Argumental movement, Criterial movement,
Locality effects, Strong Island conditions, cross-serial dependencies,
covert movement and parameter setting will be explored.





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