Probabilistic retrieval models - relationships, context-specific application, selection and implementation

PhDRetrieval models are the core components of information retrieval systems, which guide the document and query representations, as well as the document ranking schemes. TF-IDF, binary independence retrieval (BIR) model and language modelling (LM) are three of the most influential contemporary models due to their stability and performance. The BIR model and LM have probabilistic theory as their basis, whereas TF-IDF is viewed as a heuristic model, whose theoretical justification always fascinates researchers. This thesis firstly investigates the parallel derivation of BIR model, LM and Poisson model, wrt event spaces, relevance assumptions and ranking rationales. It establishes a bridge between the BIR model and LM, and derives TF-IDF from the probabilistic framework. Then, the thesis presents the probabilistic logical modelling of the retrieval models. Various ways of how to estimate and aggregate probability, and alternative implementation to nonprobabilistic operator are demonstrated. Typical models have been implemented. The next contribution concerns the usage of of context-specific frequencies, i.e., the frequencies counted based on assorted element types or within different text scopes. The hypothesis is that they can help to rank the elements in structured document retrieval. The thesis applies context-specific frequencies on term weighting schemes in these models, and the outcome is a generalised retrieval model with regard to both element and document ranking. The retrieval models behave differently on the same query set: for some queries, one model performs better, for other queries, another model is superior. Therefore, one idea to improve the overall performance of a retrieval system is to choose for each query the model that is likely to perform the best. This thesis proposes and empirically explores the model selection method according to the correlation of query feature and query performance, which contributes to the methodology of dynamically choosing a model. In summary, this thesis contributes a study of probabilistic models and their relationships, the probabilistic logical modelling of retrieval models, the usage and effect of context-specific frequencies in models, and the selection of retrieval models

The study of probability model for compound similarity searching

Information Retrieval or IR system main task is to retrieve relevant documents according to the users query. One of IR most popular retrieval model is the Vector Space Model. This model assumes relevance based on similarity, which is defined as the distance between query and document in the concept space. All currently existing chemical compound database systems have adapt the vector space model to calculate the similarity of a database entry to a query compound. However, it assumes that fragments represented by the bits are independent of one another, which is not necessarily true. Hence, the possibility of applying another IR model is explored, which is the Probabilistic Model, for chemical compound searching. This model estimates the probabilities of a chemical structure to have the same bioactivity as a target compound. It is envisioned that by ranking chemical structures in decreasing order of their probability of relevance to the query structure, the effectiveness of a molecular similarity searching system can be increased. Both fragment dependencies and independencies assumption are taken into consideration in achieving improvement towards compound similarity searching system. After conducting a series of simulated similarity searching, it is concluded that PM approaches really did perform better than the existing similarity searching. It gave better result in all evaluation criteria to confirm this statement. In terms of which probability model performs better, the BD model shown improvement over the BIR model

Retrieval of Spoken Documents: First Experiences (Research Report TR-1997-34)

We report on our first experiences in dealing with the retrieval of spoken documents. While lacking the tools and know-how for performing speech recognition on the spoken documents, we tried to use in the best possible way our knowledge of probabilistic indexing and retrieval of textual documents. The techniques we used and the results we obtained are encouraging, motivating our future involvement in other further experimentation in this new area of research

Classical and Probabilistic Information Retrieval Techniques: An Audit

Information retrieval is acquiring particular information from large resources and presenting it according to the user’s need. The incredible increase in information resources on the Internet formulates the information retrieval procedure, a monotonous and complicated task for users. Due to over access of information, better methodology is required to retrieve the most appropriate information from different sources. The most important information retrieval methods include the probabilistic, fuzzy set, vector space, and boolean models. Each of these models usually are used for evaluating the connection between the question and the retrievable documents. These methods are based on the keyword and use lists of keywords to evaluate the information material. In this paper, we present a survey of these models so that their working methodology and limitations are discussed. This is an important understanding because it makes possible to select an information retrieval technique based on the basic requirements. The survey results showed that the existing model for knowledge recovery is somewhere short of what was planned. We have also discussed different areas of IR application where these models could be used

Search beyond traditional probabilistic information retrieval

"This thesis focuses on search beyond probabilistic information retrieval. Three ap- proached are proposed beyond the traditional probabilistic modelling. First, term associ- ation is deeply examined. Term association considers the term dependency using a factor analysis based model, instead of treating each term independently. Latent factors, con- sidered the same as the hidden variables of ""eliteness"" introduced by Robertson et al. to gain understanding of the relation among term occurrences and relevance, are measured by the dependencies and occurrences of term sequences and subsequences. Second, an entity-based ranking approach is proposed in an entity system named ""EntityCube"" which has been released by Microsoft for public use. A summarization page is given to summarize the entity information over multiple documents such that the truly relevant entities can be highly possibly searched from multiple documents through integrating the local relevance contributed by proximity and the global enhancer by topic model. Third, multi-source fusion sets up a meta-search engine to combine the ""knowledge"" from different sources. Meta-features, distilled as high-level categories, are deployed to diversify the baselines. Three modified fusion methods are employed, which are re- ciprocal, CombMNZ and CombSUM with three expanded versions. Through extensive experiments on the standard large-scale TREC Genomics data sets, the TREC HARD data sets and the Microsoft EntityCube Web collections, the proposed extended models beyond probabilistic information retrieval show their effectiveness and superiority.

PubMed related articles: a probabilistic topic-based model for content similarity

<p>Abstract</p> <p>Background</p> <p>We present a probabilistic topic-based model for content similarity called <it>pmra </it>that underlies the related article search feature in PubMed. Whether or not a document is about a particular topic is computed from term frequencies, modeled as Poisson distributions. Unlike previous probabilistic retrieval models, we do not attempt to estimate relevance–but rather our focus is "relatedness", the probability that a user would want to examine a particular document given known interest in another. We also describe a novel technique for estimating parameters that does not require human relevance judgments; instead, the process is based on the existence of MeSH ^®in MEDLINE ^®.</p> <p>Results</p> <p>The <it>pmra </it>retrieval model was compared against <it>bm25</it>, a competitive probabilistic model that shares theoretical similarities. Experiments using the test collection from the TREC 2005 genomics track shows a small but statistically significant improvement of <it>pmra </it>over <it>bm25 </it>in terms of precision.</p> <p>Conclusion</p> <p>Our experiments suggest that the <it>pmra </it>model provides an effective ranking algorithm for related article search.</p

El modelo probabilístico: características y modelos derivados

A review of the art of the family of probabilistic model of information retrieval is presented. Based on its basic priciples, difefferent specific models are analysed: the BIR model –the most basic one– the classic BM25 and the DFR models, one of the last developed.Presentamos en este trabajo una revisión del estado del arte de la familia de los modelos probabilísticas de recuperación de información. Partiendo de los principios básicos que sustentan estos modelos, estudiaremos diferentes modelos concretos: el modelo de independencia binaria –el más básico–, el ya clásico BM25 y, finalmente, los modelos DFR –uno de los últimos desarrollos–