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The thesis describes novel techniques and algorithms for the practical parsing of realistic Natural Language (NL) texts with a wide-coverage unification-based grammar of English. The thesis tackles two of the major problems in this area: firstly, the fact that parsing realistic inputs with such grammars can be computationally very expensive, and secondly, the observation that many analyses are often assigned to an input, only one of which usually forms the basis of the correct interpretation. The thesis starts by presenting a new unification algorithm, justifies why it is well-suited to practical NL parsing, and describes a bottom-up active chart parser which employs this unification algorithm together with several other novel processing and optimisation techniques. Empirical results demonstrate that an implementation of this parser has significantly better practical

The ParseTalk model of concurrent, object-oriented natural language parsing is introduced. It builds upon the complete lexical distribution of grammatical knowledge and incorporates inheritance mechanisms in order to express generalizations over sets of lexical items. The grammar model integrates declarative well-formedness criteria constraining linguistic relations between heads and modifiers, and procedural specifications of the communication protocol for establishing these relations. The parser's computation model relies upon the actor paradigm, with concurrency entering through asynchronous message passing. We consider various extensions of the basic actor model as required for distributed natural language understanding and elaborate on the semantics of the actor computation model in terms of event type networks (a graph representation for actor grammar specifications) and event networks (graphs which represent the actor parser's behavior). Besides theoretical claims, we present an interactive grammar/parser workbench, a graphical development environment with various types of browsers, tracers, inspectors and debuggers that has been adapted to the requirements of large-scale grammar engineering in a distributed, object-oriented specification and programming framework.

In this report we present a Prolog tool for the development and testing of natural language grammars called GTU (German: Grammatik-Testumgebung; grammar test environment). GTU offers a window-oriented user interface that allows the development and testing of natural language grammars under three formalisms. In particular it contains a collection of German test sentences and two types of German lexicons. Both of the lexicons can be adapted to a given grammar via an integrated lexicon interface. GTU has been implemented in Prolog both under DOS and UNIX. It was originally developed as a tutoring tool to support university courses on syntax analysis but in its UNIX-version it allows for the development of large grammars. 1 Introduction Any computer system that analyses natural language input (be it a grammar checker or a tool for machine aided translation or the like) needs a formal grammar in order to map the input to a structure that groups it in some meaningful way. However, it is by ...

In this paper we describe the ideas behind the Grammar Workbench (GWB). The GWB is one of a series of tools for the development of AGFLs (affix grammars over a finite lattice) for natural languages. Its functions comprise a specialised editor, computation of properties, a random generator of sentences, and special functions to provide an overview of a grammar. This paper discusses the functions of the GWB, the grammatical formalism AGFLs, and the AGFL project. We also discuss the relationship between the complete development environment for AGFLs and other development environments, both for other grammatical formalisms and for computer programs. 1 Introduction Formal grammars for natural languages tend to become unmanageable as they get larger. Similar problems occur in the development of large computer programs. To overcome these problems with large programs, a number of techniques have been invented in the field of software engineering to ffl structure programs so as to permit deco...

The ParseTalk model of concurrent, object-oriented natural language parsing is introduced. It builds upon the complete lexical distribution of grammatical knowledge and incorporates inheritance mechanisms in order to express generalizations over sets of lexical items. The grammar model integrates declarative well-formedness criteria constraining linguistic relations between heads and modifiers, and procedural specifications of the communication protocol for establishing these relations. The parser's computation model relies upon the actor paradigm, with concurrency entering through asynchronous message passing. We consider various extensions of the basic actor model as required for distributed natural language understanding and elaborate on the semantics of the actor computation model in terms of event type networks (a graph representation for actor grammar specifications) and event networks (graphs which represent the actor parser's behavior). Besides theoretical claims, we present an interactive grammar/parser workbench, a graphical development environment with various types of browsers, tracers, inspectors and debuggers that has been adapted to the requirements of large-scale grammar engineering in a distributed, object-oriented specification and programming framework. 2 1

A review of previous work in the field of learner modelling reveals an emphasis on the surface descriptions of errors of understanding with only partial consideration of the underlying misconceptions that might explain the cause of the errors. Within a general framework for learner modelling we propose a technique, involving the use of a structured interface, for the effective acquisition of a richer and deeper model of learners' errors. The technique is considered from the perspective of a concrete domain: second language learning. Key-words: Learner Modelling, Knowledge Acquisition, Intelligent Tutoring Systems, Second Language Learning. 1. Introduction Problems associated with the acquisition of knowledge about "what" and "how" a learner understands are a stumbling block to the provision of more flexible instruction which is better adapted to the learner. This paper presents the results of initial experiments on a technique to support the acquisition of a richer knowledge about le...

Developing and, above all, maintaining a large, broad-coverage parser can be a serious exercise in software engineering. While a parser trained on an annotated corpus may be maintained by retraining on another corpus, such corpora are scarce enough for much parserwriting to require linguistic introspection. We argue that intuitiveness and readability of the underlying grammar is an essential property of a successful parser, and that it helps a lot if the results are also intuitive and readable. Given such intuitiveness, it is easier to achieve the parser's robustness, improve its coverage and its portability to new domains and applications, and generally to increase its usefulness.