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Title:Formal and Computational Aspects of Optimality-theoretic Syntax [Dissertation]
Authors:Jonas Kuhn
Comment:Dissertation, Univ. Stuttgart (2 pages on 1 sheet)
Abstract:In this dissertation, I propose a formal framework for stating in
detail a class of Optimality-Theoretic models for syntax. I discuss
empirical consequences of the key choices in the formalization and
investigate computational properties of the models, in particular
decidability of the parsing and generation tasks.

The candidate analyses I assume are non-derivational, represented as
tuples of parallel representation structures whose elements stand
in a correspondence relation in the style of Lexical-Functional
Grammar (LFG). The assumption of this type of candidates is
motivated by learnability considerations and has the advantage that
one can exploit formal and computational results for LFG and related
grammar formalisms. The formalization I discuss (in chapter 4)
builds on Joan Bresnan's original proposal of casting Optimality-
Theoretic Syntax in an LFG setting (OT-LFG). The set of all
possible candidates is specified by a formal LFG-style grammar; a
particular candidate set is defined as those possible candidates
whose functional (f-)structure is subsumed by an f-structure
representing the input. OT constraints are specified as structural
description schemata using the primitives of LFG. I discuss details
of the status of candidates violating Faithfulness constraints, as
they are required to derive expletive elements (like English do) and
non-overt elements (like in pro-drop). I argue that in OT-LFG,
Faithfulness violations can be modelled very naturally as a tension
between a candidate's f-structure and its categorial structure and
lexical material. Thus the subsumption-based definition of
candidate sets can be kept up without implying an overly restricted
candidate generation function Gen; in this formal model all language
differences can be viewed as an effect of constraint (re-)ranking.

Besides the standard production-based (or expressive) optimization
model, I discuss comprehension-based (or interpretive) optimization,
in which the terminal string is fixed across the members of the
candidate set (chapter 5). Formally, this is only a minor
modification of the definition of the candidate set, but there are
interesting conceptual and empirical issues concerning parallelism
between the two 'directions' of optimization, and in particular the
combination of both in a bidirectional model. I present a
bidirectional account of pro-drop in Italian, which derives a
recoverability condition as an effect of the interaction of the two

Building on computational results for LFG generation, I discuss the
processing tasks associated with the two types of uni-directional
optimization models and with their combination in a bidirectional
system (chapter 6). The two main issues in processing are the
control of the infinite candidate set and directionality of
processing. I show that generally, the conceptually and
empirically well-motivated formalization that I argue for provides
a sufficiently restricted basis for a computational account. While
parsing (and generation) with an unrestricted OT Syntax system is
undecidable in the general case, decidability is guaranteed if
either a recoverability condition based on a finite context
representation is assumed, or a specific type of bidirectional
model (with strong bidirectionality) is applied.
Area/Keywords:Syntax,Computation,Formal Analysis
Article:Version 1