Predicting the Effectiveness of Self-Training: Application to Sentiment Classification

The goal of this paper is to investigate the connection between the performance gain that can be obtained by selftraining and the similarity between the corpora used in this approach. Self-training is a semi-supervised technique designed to increase the performance of machine learning algorithms by automatically classifying instances of a task and adding these as additional training material to the same classifier. In the context of language processing tasks, this training material is mostly an (annotated) corpus. Unfortunately self-training does not always lead to a performance increase and whether it will is largely unpredictable. We show that the similarity between corpora can be used to identify those setups for which self-training can be beneficial. We consider this research as a step in the process of developing a classifier that is able to adapt itself to each new test corpus that it is presented with

Detection of Compound Word with Combination Noun and Adjective using Rule Based Technique in Malay Standard Document

In this paper we describe our methods for detecting the compound word with combination of Noun and Adjective Compound Nouns in Malay standard document. We addressed the problem on detection of combination noun and adjective in Malay sentences to become a compound word. We modified several identification rules based by using Malay grammar rules and syntactic information to increase the percentage of recall, precision and F1-Score. For compound word identification, we used dictionary-based and thesaurus information for implementing Part of Speech (POS) tagging to all words in the selected Malay document. Testing was done on selected Malay document. The result showed an improvement compared to previous research with a precision of 90.9%, a recall of 10.2% and a F1-Score of 18.1%

Textual Data Selection for Language Modelling in the Scope of Automatic Speech Recognition

International audienceThe language model is an important module in many applications that produce natural language text, in particular speech recognition. Training of language models requires large amounts of textual data that matches with the target domain. Selection of target domain (or in-domain) data has been investigated in the past. For example [1] has proposed a criterion based on the difference of cross-entropy between models representing in-domain and non-domain-specific data. However evaluations were conducted using only two sources of data, one corresponding to the in-domain, and another one to generic data from which sentences are selected. In the scope of broadcast news and TV shows transcription systems, language models are built by interpolating several language models estimated from various data sources. This paper investigates the data selection process in this context of building interpolated language models for speech transcription. Results show that, in the selection process, the choice of the language models for representing in-domain and non-domain-specific data is critical. Moreover, it is better to apply the data selection only on some selected data sources. This way, the selection process leads to an improvement of 8.3 in terms of perplexity and 0.2% in terms of word-error rate on the French broadcast transcription task

Language modeling for speech recognition of spoken Cantonese.

Yeung, Yu Ting.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (leaves 84-93).Abstracts in English and Chinese.Acknowledgement --- p.iiiAbstract --- p.ivChapter 1 --- Introduction --- p.1Chapter 1.1 --- Cantonese Speech Recognition --- p.3Chapter 1.2 --- Objectives --- p.4Chapter 1.3 --- Thesis Outline --- p.5Chapter 2 --- Fundamentals of Large Vocabulary Continuous Speech Recognition --- p.7Chapter 2.1 --- Problem Formulation --- p.7Chapter 2.2 --- Feature Extraction --- p.8Chapter 2.3 --- Acoustic Models --- p.9Chapter 2.4 --- Decoding --- p.10Chapter 2.5 --- Statistical Language Modeling --- p.12Chapter 2.5.1 --- N-gram Language Models --- p.12Chapter 2.5.2 --- N-gram Smoothing --- p.13Chapter 2.5.3 --- Complexity of Language Model --- p.15Chapter 2.5.4 --- Class-based Langauge Model --- p.16Chapter 2.5.5 --- Language Model Pruning --- p.17Chapter 2.6 --- Performance Evaluation --- p.18Chapter 3 --- The Cantonese Dialect --- p.19Chapter 3.1 --- Phonology of Cantonese --- p.19Chapter 3.2 --- Orthographic Representation of Cantonese --- p.22Chapter 3.3 --- Classification of Cantonese speech --- p.25Chapter 3.4 --- Cantonese-English Code-mixing --- p.27Chapter 4 --- Rule-based Translation Method --- p.29Chapter 4.1 --- Motivations --- p.29Chapter 4.2 --- Transformation-based Learning --- p.30Chapter 4.2.1 --- Algorithm Overview --- p.30Chapter 4.2.2 --- Learning of Translation Rules --- p.32Chapter 4.3 --- Performance Evaluation --- p.35Chapter 4.3.1 --- The Learnt Translation Rules --- p.35Chapter 4.3.2 --- Evaluation of the Rules --- p.37Chapter 4.3.3 --- Analysis of the Rules --- p.37Chapter 4.4 --- Preparation of Training Data for Language Modeling --- p.41Chapter 4.5 --- Discussion --- p.43Chapter 5 --- Language Modeling for Cantonese --- p.44Chapter 5.1 --- Training Data --- p.44Chapter 5.1.1 --- Text Corpora --- p.44Chapter 5.1.2 --- Preparation of Formal Cantonese Text Data --- p.45Chapter 5.2 --- Training of Language Models --- p.46Chapter 5.2.1 --- Language Models for Standard Chinese --- p.46Chapter 5.2.2 --- Language Models for Formal Cantonese --- p.46Chapter 5.2.3 --- Language models for Colloquial Cantonese --- p.47Chapter 5.3 --- Evaluation of Language Models --- p.48Chapter 5.3.1 --- Speech Corpora for Evaluation --- p.48Chapter 5.3.2 --- Perplexities of Formal Cantonese Language Models --- p.49Chapter 5.3.3 --- Perplexities of Colloquial Cantonese Language Models --- p.51Chapter 5.4 --- Speech Recognition Experiments --- p.53Chapter 5.4.1 --- Speech Corpora --- p.53Chapter 5.4.2 --- Experimental Setup --- p.54Chapter 5.4.3 --- Results on Formal Cantonese Models --- p.55Chapter 5.4.4 --- Results on Colloquial Cantonese Models --- p.56Chapter 5.5 --- Analysis of Results --- p.58Chapter 5.6 --- Discussion --- p.59Chapter 5.6.1 --- Cantonese Language Modeling --- p.59Chapter 5.6.2 --- Interpolated Language Models --- p.59Chapter 5.6.3 --- Class-based Language Models --- p.60Chapter 6 --- Towards Language Modeling of Code-mixing Speech --- p.61Chapter 6.1 --- Data Collection --- p.61Chapter 6.1.1 --- Data Collection --- p.62Chapter 6.1.2 --- Filtering of Collected Data --- p.63Chapter 6.1.3 --- Processing of Collected Data --- p.63Chapter 6.2 --- Clustering of Chinese and English Words --- p.64Chapter 6.3 --- Language Modeling for Code-mixing Speech --- p.64Chapter 6.3.1 --- Language Models from Collected Data --- p.64Chapter 6.3.2 --- Class-based Language Models --- p.66Chapter 6.3.3 --- Performance Evaluation of Code-mixing Language Models --- p.67Chapter 6.4 --- Speech Recognition Experiments with Code-mixing Language Models --- p.69Chapter 6.4.1 --- Experimental Setup --- p.69Chapter 6.4.2 --- Monolingual Cantonese Recognition --- p.70Chapter 6.4.3 --- Code-mixing Speech Recognition --- p.72Chapter 6.5 --- Discussion --- p.74Chapter 6.5.1 --- Data Collection from the Internet --- p.74Chapter 6.5.2 --- Speech Recognition of Code-mixing Speech --- p.75Chapter 7 --- Conclusions and Future Work --- p.77Chapter 7.1 --- Conclusions --- p.77Chapter 7.1.1 --- Rule-based Translation Method --- p.77Chapter 7.1.2 --- Cantonese Language Modeling --- p.78Chapter 7.1.3 --- Code-mixing Language Modeling --- p.78Chapter 7.2 --- Future Works --- p.79Chapter 7.2.1 --- Rule-based Translation --- p.79Chapter 7.2.2 --- Training data --- p.80Chapter 7.2.3 --- Code-mixing speech --- p.80Chapter A --- Equation Derivation --- p.82Chapter A.l --- Relationship between Average Mutual Information and Perplexity --- p.82Bibliography --- p.8

A Corpus-based Approach to the Chinese Word Segmentation

For a society based upon laws and reason, it has become too easy for us to believe that we live in a world without them. And given that our linguistics wisdom was originally motivated by the search for rules, it seems strange that we now consider these rules to be the exceptions and take exceptions as the norm. The current task of contemporary computational linguistics is to describe these exceptions. In particular, it suffices for most language processing needs, to just describe the argument and predicate within an elementary sentence, under the framework of local grammar. Therefore, a corpus-based approach to the Chinese Word Segmentation problem is proposed, as the first step towards a local grammar for the Chinese language. The two main issues with existing lexicon-based approaches are (a) the classification of unknown character sequences, i.e. sequences that are not listed in the lexicon, and (b) the disambiguation of situations where two candidate words overlap. For (a), we propose an automatic method of enriching the lexicon by comparing candidate sequences to occurrences of the same strings in a manually segmented reference corpus, and using methods of machine learning to select the optimal segmentation for them. These methods are developed in the course of the thesis specifically for this task. The possibility of applying these machine learning method will be discussed in NP-extraction and alignment domain. (b) is approached by designing a general processing framework for Chinese text, which will be called multi-level processing. Under this framework, sentences are recursively split into fragments, according to a language-specific, but domainindependent heuristics. The resulting fragments then define the ultimate boundaries between candidate words and therefore resolve any segmentation ambiguity caused by overlapping sequences. A new shallow semantical annotation is also proposed under the frame work of multi-level processing. A word segmentation algorithm based on these principles has been implemented and tested; results of the evaluation are given and compared to the performance of previous approaches as reported in the literature. The first chapter of this thesis discusses the goals of segmentation and introduces some background concepts. The second chapter analyses the current state-of-theart approach to Chinese language segmentation. Chapter 3 proposes a new corpusbased approach to the identification of unknown words. In chapter 4, a new shallow semantical annotation is also proposed under the framework of multi-level processing

Using Comparable Corpora to Augment Statistical Machine Translation Models in Low Resource Settings

Previously, statistical machine translation (SMT) models have been estimated from parallel corpora, or pairs of translated sentences. In this thesis, we directly incorporate comparable corpora into the estimation of end-to-end SMT models. In contrast to parallel corpora, comparable corpora are pairs of monolingual corpora that have some cross-lingual similarities, for example topic or publication date, but that do not necessarily contain any direct translations. Comparable corpora are more readily available in large quantities than parallel corpora, which require significant human effort to compile. We use comparable corpora to estimate machine translation model parameters and show that doing so improves performance in settings where a limited amount of parallel data is available for training. The major contributions of this thesis are the following: * We release ‘language packs’ for 151 human languages, which include bilingual dictionaries, comparable corpora of Wikipedia document pairs, comparable corpora of time-stamped news text that we harvested from the web, and, for non-roman script languages, dictionaries of name pairs, which are likely to be transliterations. * We present a novel technique for using a small number of example word translations to learn a supervised model for bilingual lexicon induction which takes advantage of a wide variety of signals of translation equivalence that can be estimated over comparable corpora. * We show that using comparable corpora to induce new translations and estimate new phrase table feature functions improves end-to-end statistical machine translation performance for low resource language pairs as well as domains. * We present a novel algorithm for composing multiword phrase translations from multiple unigram translations and then use comparable corpora to prune the large space of hypothesis translations. We show that these induced phrase translations improve machine translation performance beyond that of component unigrams. This thesis focuses on critical low resource machine translation settings, where insufficient parallel corpora exist for training statistical models. We experiment with both low resource language pairs and low resource domains of text. We present results from our novel error analysis methodology, which show that most translation errors in low resource settings are due to unseen source language words and phrases and unseen target language translations. We also find room for fixing errors due to how different translations are weighted, or scored, in the models. We target both error types; we use comparable corpora to induce new word and phrase translations and estimate novel translation feature scores. Our experiments show that augmenting baseline SMT systems with new translations and features estimated over comparable corpora improves translation performance significantly. Additionally, our techniques expand the applicability of statistical machine translation to those language pairs for which zero parallel text is available

Toward a Unified Approach to Statistical Language Modeling for Chinese

This paper presents a unified approach to Chinese statistical language modeling (SLM). Applying SLM techniques like trigram language models to Chinese is challenging because (1) there is no standard definition of words in Chinese, (2) word boundaries are not marked by spaces, and (3) there is a dearth of training data. Our unified approach automatically and consistently gathers a highquality training data set from the web, creates a high-quality lexicon, segments the training data using this lexicon, and compresses the language model, all using the maximum likelihood principle, which is consistent with the trigram model training. We show that each of the methods leads to improvements over standard SLM, and that the combined method yields the best pinyin conversion result reported