Syntactic analysis of natural languages based on context-free grammar backbone

Mgr. Vladimír Kadlec, Ph.D.

Doctoral thesis

Abstract:

The aim of the thesis is to design algorithms and methods for an effective and robust syntactic analysis of natural languages. The algorithms are language-independent, any language with an appropriate grammar can be modeled. The analysis of sentences by the described system is based on context-free grammar for a given language supplemented by context sensitive structures. The internal representation of derivation trees allows applying contextual constraints, e.g. case agreement fulfillment. The result of the constraint application is still stored in the polynomial structure. The evaluation of semantic actions and contextual constraints helps us to reduce a huge number of derivation trees and we are also able to calculate some new information, which is not contained in the context-free part of the grammar. Also n-best trees (according to a tree rank, e.g. probability) can be selected. This is an important feature for linguistics developing a grammar by hand. We describe a robust extension of our parser that is able to return a "correct" derivation tree even if the grammar cannot generate the input sentence. Because the presented system is language-independent, results for English and French grammars are provided, as well as results for Czech.

Keywords

nlp, parsing, cfg, grammar, czech

Language used: English

Date on which the thesis was submitted / produced: 21. 1. 2008

Thesis defence

• Date of defence: 26. 2. 2008
• Supervisor: prof. PhDr. Karel Pala, CSc.
• Reader: doc. RNDr. Martin Plátek, Dr. Martin Rajman

Masaryk University

Faculty of Informatics

Doctoral programme / field:
Informatics (4-years) / Informatics