Word sense disambiguation and information retrieval

It has often been thought that word sense ambiguity is a cause of poor performance in Information Retrieval (IR) systems. The belief is that if ambiguous words can be correctly disambiguated, IR performance will increase. However, recent research into the application of a word sense disambiguator to an IR system failed to show any performance increase. From these results it has become clear that more basic research is needed to investigate the relationship between sense ambiguity, disambiguation, and IR. Using a technique that introduces additional sense ambiguity into a collection, this paper presents research that goes beyond previous work in this field to reveal the influence that ambiguity and disambiguation have on a probabilistic IR system. We conclude that word sense ambiguity is only problematic to an IR system when it is retrieving from very short queries. In addition we argue that if a word sense disambiguator is to be of any use to an IR system, the disambiguator must be able to resolve word senses to a high degree of accuracy

Word sense disambiguation and information retrieval

It has often been thought that word sense ambiguity is a cause of poor performance in Information Retrieval (IR) systems. The belief is that if ambiguous words can be correctly disambiguated, IR performance will increase. However, recent research into the application of a word sense disambiguator to an IR system failed to show any performance increase. From these results it has become clear that more basic research is needed to investigate the relationship between sense ambiguity, disambiguation, and IR. Using a technique that introduces additional sense ambiguity into a collection, this paper presents research that goes beyond previous work in this field to reveal the influence that ambiguity and disambiguation have on a probabilistic IR system. We conclude that word sense ambiguity is only problematic to an IR system when it is retrieving from very short queries. In addition we argue that if a word sense disambiguator is to be of any use to an IR system, the disambiguator must be able to resolve word senses to a high degree of accuracy

Pragmatic linguistic constraint models for large-vocabulary speech processing

Current systems for speech recognition suffer from uncertainty: rather than delivering a uniquely-identified word, each input segment is associated with a set of recognition candidates or word-hypotheses. Thus an input sequence of sounds or images leads to, not an unambiguous sequence of words, but a lattice of word-hypotheses. To choose the best candidate from each word-hypothesis set (i.e. to find the best route through the lattice) , linguistic context needs to be taken into account, at several levels: lexis and morphology, parts-of-speech, phrase structure, semantics and pragmatics. We believe that an intuitively simple, naive model will suffice at each level; the sophistication required for full Natural Language Understanding (NLU) (e.g. Alvey Natural Language Toolkit (ANLT)) is inappropriate for real-time language recognition. We describe here models of each linguistic level which are simple but robust and computationally straightforward (hence `pragmatic' in the everyday sense) and which have clear theoretical shortcomings in the eyes of linguistic purists but which nevertheless do the job

Sense resolution properties of logical imaging

The evaluation of an implication by Imaging is a logical technique developed in the framework of modal logic. Its interpretation in the context of a “possible worlds” semantics is very appealing for IR. In 1994, Crestani and Van Rijsbergen proposed an interpretation of Imaging in the context of IR based on the assumption that “a term is a possibleworld”. This approach enables the exploitation of term– term relationshipswhich are estimated using an information theoretic measure. Recent analysis of the probability kinematics of Logical Imaging in IR have suggested that this technique has some interesting sense resolution properties. In this paper we will present this new line of research and we will relate it to more classical research into word senses

Multi-level disambiguation grammar inferred from English Corpus, treebank, and dictionary

It is shown that grammatical inference is applicable to natural language processing. Given the wide and complex range of structures appearing in an unrestricted natural language like English, full grammatical inference, yielding a comprehensive syntactic and semantic definition of English, is too much to hope for at present. Instead, the authors focus on techniques for dealing with ambiguity resolution by probabilistic ranking; this does not require a full formal Chomskyan grammar. They give a short overview of the different levels and methods being investigated at CCALAS for probabilistic ranking of candidates in ambiguous English input

Corpus linguistics and language learning: bootstrapping linguistic knowledge and resources from text

This submission for the award of the degree of PhD by published work must: “make a contribution to knowledge in a coherent and related subject area; demonstrate originality and independent critical ability; satisfy the examiners that it is of sufficient merit to qualify for the award of the degree of PhD.” It includes a selection of my work as a Lecturer (and later, Senior Lecturer) at Leeds University, from 1984 to the present. The overall theme of my research has been bootstrapping linguistic knowledge and resources from text. A persistent strand of interest has been unsupervised and semi-supervised machine learning of linguistic knowledge from textual sources; the attraction of this approach is that I could start with English, but go on to apply analogous techniques to other languages, in particular Arabic. This theme covers a broad range of research over more than 20 years at Leeds University which I have divided into 8 sub-topics: A: Constituent-Likelihood statistical modelling of English grammar; B: Machine Learning of grammatical patterns from a corpus; C: Detecting grammatical errors in English text; D: Evaluation of English grammatical annotation models; E: Machine Learning of semantic language models; F: Applications in English language teaching; G: Arabic corpus linguistics; H: Applications in Computing teaching and research. The first section builds on my early years as a lecturer at Leeds University, when my research was essentially a progression from my previous work at Lancaster University on the LOB Corpus Part-of-Speech Tagging project (which resulted in the Tagged LOB Corpus, a resource for Corpus Linguistics research still in use today); I investigated a range of ideas for extending and/or applying techniques related to Part-of-Speech tagging in Corpus Linguistics. The second section covers a range of co-authored papers representing grant-funded research projects in Corpus Linguistics; in this mode of research, I had to come up with the original ideas and guide the project, but much of the detailed implementation was down to research assistant staff. Another highly productive mode of research has been supervision of research students, leading to further jointly-authored research papers. I helped formulate the research plans, and guided and advised the students; as with research-grant projects, the detailed implementation of the research has been down to the research students. The third section includes a few of the most significant of these jointly-authored Corpus Linguistics research papers. A “standard” PhD generally includes a survey of the field to put the work in context; so as a fourth section, I include some survey papers aimed at introducing new developments in corpus linguistics to a wider audience

Domain-Specific Knowledge Acquisition for Conceptual Sentence Analysis

The availability of on-line corpora is rapidly changing the field of natural language processing (NLP) from one dominated by theoretical models of often very specific linguistic phenomena to one guided by computational models that simultaneously account for a wide variety of phenomena that occur in real-world text. Thus far, among the best-performing and most robust systems for reading and summarizing large amounts of real-world text are knowledge-based natural language systems. These systems rely heavily on domain-specific, handcrafted knowledge to handle the myriad syntactic, semantic, and pragmatic ambiguities that pervade virtually all aspects of sentence analysis. Not surprisingly, however, generating this knowledge for new domains is time-consuming, difficult, and error-prone, and requires the expertise of computational linguists familiar with the underlying NLP system. This thesis presents Kenmore, a general framework for domain-specific knowledge acquisition for conceptual sentence analysis. To ease the acquisition of knowledge in new domains, Kenmore exploits an on-line corpus using symbolic machine learning techniques and robust sentence analysis while requiring only minimal human intervention. Unlike most approaches to knowledge acquisition for natural language systems, the framework uniformly addresses a range of subproblems in sentence analysis, each of which traditionally had required a separate computational mechanism. The thesis presents the results of using Kenmore with corpora from two real-world domains (1) to perform part-of-speech tagging, semantic feature tagging, and concept tagging of all open-class words in the corpus; (2) to acquire heuristics for part-ofspeech disambiguation, semantic feature disambiguation, and concept activation; and (3) to find the antecedents of relative pronouns

Parallel parsing made practical

The property of local parsability allows to parse inputs through inspecting only a bounded-length string around the current token. This in turn enables the construction of a scalable, data-parallel parsing algorithm, which is presented in this work. Such an algorithm is easily amenable to be automatically generated via a parser generator tool, which was realized, and is also presented in the following. Furthermore, to complete the framework of a parallel input analysis, a parallel scanner can also combined with the parser. To prove the practicality of a parallel lexing and parsing approach, we report the results of the adaptation of JSON and Lua to a form fit for parallel parsing (i.e. an operator-precedence grammar) through simple grammar changes and scanning transformations. The approach is validated with performance figures from both high performance and embedded multicore platforms, obtained analyzing real-world inputs as a test-bench. The results show that our approach matches or dominates the performances of production-grade LR parsers in sequential execution, and achieves significant speedups and good scaling on multi-core machines. The work is concluded by a broad and critical survey of the past work on parallel parsing and future directions on the integration with semantic analysis and incremental parsing