An important part of our information-gathering behavior has always been to find out what other people think. With the growing availability and popularity of opinion-rich resources such as online review sites and personal blogs, new opportunities and challenges arise as people now can, and do, actively use information technologies to seek out and understand the opinions of others. The sudden eruption of activity in the area of opinion mining and sentiment analysis, which deals with the computational treatment of opinion, sentiment, and subjectivity in text, has thus occurred at least in part as a direct response to the surge of interest in new systems that deal directly with opinions as a first-class object.

This survey covers techniques and approaches that promise to directly enable opinion-oriented information-seeking systems. Our focus is on methods that seek to address the new challenges raised by sentiment-aware applications, as compared to those that are already present in more traditional fact-based analysis. We include material on summarization of evaluative text and on broader issues regarding privacy, manipulation, and economic impact that the development of opinion-oriented information-access services gives rise to. To facilitate future work, a discussion of available resources, benchmark datasets, and evaluation campaigns is also provided.

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Opinion Mining and Sentiment Analysis

In today's world, there is no shortage of information. However, for a specific information need, only a small subset of all of the available information will be useful. The field of information retrieval (IR) is the study of methods to provide users with that small subset of information relevant to their needs and to do so in a timely fashion. Information sources can take many forms, but this thesis will focus on text based information systems and investigate problems germane to the retrieval of written natural language documents.

Central to these problems is the notion of "topic." In other words, what are documents about? However, topics depend on the semantics of documents and retrieval systems are not endowed with knowledge of the semantics of natural language. The approach taken in this thesis will be to make use of probabilistic language models to investigate text based information retrieval and related problems.

One such problem is the prediction of topic shifts in text, the topic segmentation problem. It will be shown that probabilistic methods can be used to predict topic changes in the context of the task of new event detection. Two complementary sets of features are studied individually and then combined into a single language model. The language modeling approach allows this problem to be approached in a principled way without complex semantic modeling.

Next, the problem of document retrieval in response to a user query will be investigated. Models of document indexing and document retrieval have been extensively studied over the past three decades. The integration of these two classes of models has been the goal of several researchers but it is a very difficult problem. Much of the reason for this is that the indexing component requires inferences as to the semantics of documents. Instead, an approach to retrieval based on probabilistic language modeling will be presented. Models are estimated for each document individually. The approach to modeling is non-parametric and integrates the entire retrieval process into a single model. One advantage of this approach is that collection statistics, which are used heuristically for the assignment of concept probabilities in other probabilistic models, are used directly in the estimation of language model probabilities in this approach. The language modeling approach has been implemented and tested empirically and performs very well on standard test collections and query sets.

In order to improve retrieval effectiveness, IR systems use additional techniques such as relevance feedback, unsupervised query expansion and structured queries. These and other techniques are discussed in terms of the language modeling approach and empirical results are given for several of the techniques developed. These results provide further proof of concept for the use of language models for retrieval tasks.

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A language modeling approach to information retrieval

This tutorial is concerned with a comprehensive introduction to the research area of learning to rank for information retrieval. In the first part of the tutorial, we will introduce three major approaches to learning to rank, i.e., the pointwise, pairwise, and listwise approaches, analyze the relationship between the loss functions used in these approaches and the widely-used IR evaluation measures, evaluate the performance of these approaches on the LETOR benchmark datasets, and demonstrate how to use these approaches to solve real ranking applications. In the second part of the tutorial, we will discuss some advanced topics regarding learning to rank, such as relational ranking, diverse ranking, semi-supervised ranking, transfer ranking, query-dependent ranking, and training data preprocessing. In the third part, we will briefly mention the recent advances on statistical learning theory for ranking, which explain the generalization ability and statistical consistency of different ranking methods. In the last part, we will conclude the tutorial and show several future research directions.

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Learning to Rank for Information Retrieval

We explore the relation between classical probabilistic models of information retrieval and the emerging language modeling approaches. It has long been recognized that the primary obstacle to effective performance of classical models is the need to estimate a relevance model: probabilities of words in the relevant class. We propose a novel technique for estimating these probabilities using the query alone. We demonstrate that our technique can produce highly accurate relevance models, addressing important notions of synonymy and polysemy. Our experiments show relevance models outperforming baseline language modeling systems on TREC retrieval and TDT tracking tasks. The main contribution of this work is an effective formal method for estimating a relevance model with no training data.

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Relevance-Based Language Models

Language modeling approaches to information retrieval are attractive and promising because they connect the problem of retrieval with that of language model estimation, which has been studied extensively in other application areas such as speech recognition. The basic idea of these approaches is to estimate a language model for each document, and then rank documents by the likelihood of the query according to the estimated language model. A core problem in language model estimation is smoothing, which adjusts the maximum likelihood estimator so as to correct the inaccuracy due to data sparseness. In this paper, we study the problem of language model smoothing and its influence on retrieval performance. We examine the sensitivity of retrieval performance to the smoothing parameters and compare several popular smoothing methods on different test collections.

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A Study of Smoothing Methods for Language Models Applied to Ad Hoc Information Retrieval

Information retrieval (IR) research has reached a
point where it is appropriate to assess progress and
to define a research agenda for the next five to ten
years. This report summarizes a discussion of IR
research challenges that took place at a recent
workshop.
The attendees of the workshop considered
information retrieval research in a range of areas
chosen to give broad coverage of topic areas that
engage information retrieval researchers. Those
areas are retrieval models, cross-lingual retrieval,
Web search, user modeling, filtering, topic detection
and tracking, classification, summarization, question
answering, metasearch, distributed retrieval,
multimedia retrieval, information extraction, as well
as testbed requirements for future work. The
potential use of language modeling techniques in
these areas was also discussed.
The workshop identified major challenges within
each of those areas. The following are recurring
themes that ran throughout:
• User and context sensitive retrieval
• Multi-lingual and multi-media issues
• Better target tasks
• Improved objective evaluations
• Substantially more labeled data
• Greater variety of data sources
• Improved formal models
Contextual retrieval and global information access
were identified as particularly important long-term
challenges.

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Challenges in information retrieval and language modeling: report of a workshop held at the center for intelligent information retrieval, University of Massachusetts Amherst, September 2002

We investigate the problem of text segmentation by topic. Applications for this task include topic tracking of broadcast speech data and topic identification in full-text databases. Researchers have tackled similar problems before but with different goals. This study focuses on data with relatively small segment sizes and for which within-segment sentences have relatively few words in common making the problem challenging. We present a method for segmentation which makes use of a query expansion technique to find common features for the topic segments. Experiments with the technique show that it can be effective.

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Text Segmentation by Topic

Disclosed is a system for performing online data queries. The system for performing online data queries is a distributed computer system with a plurality of server nodes each fully redundant and capable of processing a user query request. Each server node includes a data query cache and other caches that may be used in performing data queries. The data query, as well as request allocation, is performed in accordance with an adaptive partitioning technique with a bias towards an initial partitioning scheme. Generic objects are created and used to represent business listings upon which the user may perform queries. Various data processing and integration techniques are included which enhance data queries. An update technique is used for synchronizing data updates as needed in updating the plurality of server nodes. A multi-media data transfer technique is used to transfer non-text or multi-media data between various components of the online query tool. Optimizations for searching, such as the common term optimization, are included for those commonly performed data queries. Also disclosed is a system for targeting advertisements that are displayed to a user of the system.

Data merging techniques

A distributed system is described that reliably mines parallel text from large corpora. The approach can be regarded as cross-language near-duplicate detection, enabled by an initial, low-quality batch translation. In contrast to other approaches which require specialized metadata, the system uses only the textual content of the documents. Results are presented for a corpus of over two billion web pages and for a large collection of digitized public-domain books.

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Jay Ponte

Papers

A language modeling approach to information retrieval

Challenges in information retrieval and language modeling: report of a workshop held at the center for intelligent information retrieval, University of Massachusetts Amherst, September 2002

Text Segmentation by Topic

Data merging techniques

Large Scale Parallel Document Mining for Machine Translation