Abstract not found

This paper presents a novel probabilistic information retrieval framework in which the retrieval problem is formally treated as a statistical decision problem. In this framework, queries and documents are modeled using statistical language models (i.e., probabilistic models of text), user preferences are modeled through loss functions, and retrieval is cast as a risk minimization problem. We discuss how this framework can unify existing retrieval models and accommodate the systematic development of new retrieval models. As an example of using the framework to model non-traditional retrieval problems, we derive new retrieval models for subtopic retrieval, which is concerned with retrieving documents to cover many different subtopics of a general query topic. These new models differ from traditional retrieval models in that they go beyond independent topical relevance.

Statistical language models have recently been successfully applied to many information retrieval problems. A great deal of recent work has shown that statistical language models not only lead to superior empirical performance, but also facilitate parameter tuning and open up possibilities for modeling nontraditional retrieval problems. In general, statistical language models provide a principled way of modeling various kinds of retrieval problems. The purpose of this survey is to systematically and critically review the existing work in applying statistical language models to information retrieval, summarize their contributions, and point out outstanding challenges. 1

Information retrieval is, in general, an iterative search process, in which the user often has several interactions with a retrieval system for an information need. The retrieval system can actively probe a user with questions to clarify the information need instead of just passively responding to user queries. A basic question is thus how a retrieval system should propose questions to the user so that it can obtain maximum benefits from the feedback on these questions. In this paper, we study how a retrieval system can perform active feedback, i.e., how to choose documents for relevance feedback so that the system can learn most from the feedback information. We present a general framework for such an active feedback problem, and derive several practical algorithms as special cases. Empirical evaluation of these algorithms shows that the performance of traditional relevance feedback (presenting the top K documents) is consistently worse than that of presenting documents with more diversity. With a diversity-based selection algorithm, we obtain fewer relevant documents, however, these fewer documents have more learning benefits.

The main aspects of XML retrieval are identified by analysing and comparing the following two behaviours: the behaviour of the assessor when judging the relevance of returned document components; and the behaviour of users when interacting with components of XML documents. We argue that the two INEX relevance dimensions, Exhaustivity and Specificity, are not orthogonal dimensions; indeed, an empirical analysis of each dimension reveals that the grades of the two dimensions are correlated to each other. By analysing the level of agreement between the assessor and the users, we aim at identifying the best units of retrieval. The results of our analysis show that the highest level of agreement is on highly relevant and on non-relevant document components, suggesting that only the end points of the INEX 10-point relevance scale are perceived in the same way by both the assessor and the users. We propose a new definition of relevance for XML retrieval and argue that its corresponding relevance scale would be a better choice for INEX. 1.

Handwritten historical document collections in libraries and other areas are often of interest to researchers, students or the general public. Convenient access to such corpora generally requires an index, which allows one to locate individual text units (pages, sentences, lines) that are relevant to a given query (usually provided as text). Several solutions are possible: manual annotation (very expensive), handwriting recognition (poor results) and word spotting - an image matching approach (computationally expensive).

Ranking blog posts that express opinions regarding a given topic should serve a critical function in helping users. We explored three types of opinion retrieval methods in the framework of probabilistic language models. The first method combines topic-relevance model and opinion-relevance model that captures topic dependence of the opinion expressions. The second method makes use of probability that any of opinion-bearing words appear in each target document as document prior probability in query-likelihood model. The third method makes use of probability that any of adjectives or adverbs appear in each target document as document prior probability, assuming opinionated documents tend to contain more adjectives or adverbs than other documents. 1

Abstract: We address the issue of combining explicit background knowledge with pseudo-relevance feedback from within a document collection. To this end, we use document-level annotations in tandem with generative language models to generate terms from pseudo-relevant documents and bias the probability estimates of expansion terms in a principled manner. By applying the knowledge inherent in document annotations, we aim to control query drift and reap the benefits of automatic query expansion in terms of recall without losing precision. We consider the parameters which are associated with our modeling and describe ways of estimating these automatically. We then evaluate our modeling and estimation methods on two test collections, both provided by the TREC Genomics track. 1

The novelty task consists of finding relevant and novel sentences in a ranking of documents given a query. In the literature, different techniques have been applied to address this problem. Nevertheless, little is known about Language Models for novelty detection and, especially, the effect of smoothing on the selection of novel sentences. Language Models can be used to study novelty and relevance in a principled way. These statistical models have been shown to perform well empirically in many Information Retrieval tasks. In this work we study formally the effects of smoothing on novelty detection. To this aim, we compare different techniques based on the Kullback-Leibler divergence and we analyze the sensitivity of retrieval performance to the smoothing parameters. The ability of Language Modeling estimation methods to handle quantitatively the uncertainty associated to the use of natural language is a powerful tool that can drive the future development of noveltybased mechanisms.

... we address are threefold: (i) what are the effects of estimating and applying relevance models to the domain specific collection used at CLEF 2008, (ii) what are the results of parsimonizing these relevance models, and (iii) what are the results of applying concept models for blind relevance feedback? Parsimonization is a technique by which the term probabilities in a language model may be re-estimated based on a comparison with a reference model, making the resulting model more sparse and to the point. Concept models are term distributions over vocabulary terms, based on the language associated with concepts in a thesaurus or ontology and are estimated using the documents which are annotated with concepts. Concept models may be used for blind relevance feedback, by first translating a query to concepts and then back to query terms. We find that applying relevance models helps significantly for the current test collection, in terms of both mean average precision and early precision. Moreover, parsimonizing the relevance models helps mean average precision on title-only queries and early precision on title+narrative queries. Our concept models are able to significantly outperform a baseline query-likelihood run, both in terms of mean average precision and early precision on both title-only and title+narrative queries.