TopSig: Topology Preserving Document Signatures

Performance comparisons between File Signatures and Inverted Files for text retrieval have previously shown several significant shortcomings of file signatures relative to inverted files. The inverted file approach underpins most state-of-the-art search engine algorithms, such as Language and Probabilistic models. It has been widely accepted that traditional file signatures are inferior alternatives to inverted files. This paper describes TopSig, a new approach to the construction of file signatures. Many advances in semantic hashing and dimensionality reduction have been made in recent times, but these were not so far linked to general purpose, signature file based, search engines. This paper introduces a different signature file approach that builds upon and extends these recent advances. We are able to demonstrate significant improvements in the performance of signature file based indexing and retrieval, performance that is comparable to that of state of the art inverted file based systems, including Language models and BM25. These findings suggest that file signatures offer a viable alternative to inverted files in suitable settings and from the theoretical perspective it positions the file signatures model in the class of Vector Space retrieval models.Comment: 12 pages, 8 figures, CIKM 201

Exploring Topic-based Language Models for Effective Web Information Retrieval

The main obstacle for providing focused search is the relative opaqueness of search request -- searchers tend to express their complex information needs in only a couple of keywords. Our overall aim is to find out if, and how, topic-based language models can lead to more effective web information retrieval. In this paper we explore retrieval performance of a topic-based model that combines topical models with other language models based on cross-entropy. We first define our topical categories and train our topical models on the .GOV2 corpus by building parsimonious language models. We then test the topic-based model on TREC8 small Web data collection for ad-hoc search.Our experimental results show that the topic-based model outperforms the standard language model and parsimonious model

Creating a test collection to evaluate diversity in image retrieval

This paper describes the adaptation of an existing test collection for image retrieval to enable diversity in the results set to be measured. Previous research has shown that a more diverse set of results often satisfies the needs of more users better than standard document rankings. To enable diversity to be quantified, it is necessary to classify images relevant to a given theme to one or more sub-topics or clusters. We describe the challenges in building (as far as we are aware) the first test collection for evaluating diversity in image retrieval. This includes selecting appropriate topics, creating sub-topics, and quantifying the overall effectiveness of a retrieval system. A total of 39 topics were augmented for cluster-based relevance and we also provide an initial analysis of assessor agreement for grouping relevant images into sub-topics or clusters

The State-of-the-arts in Focused Search

The continuous influx of various text data on the Web requires search engines to improve their retrieval abilities for more specific information. The need for relevant results to a user’s topic of interest has gone beyond search for domain or type specific documents to more focused result (e.g. document fragments or answers to a query). The introduction of XML provides a format standard for data representation, storage, and exchange. It helps focused search to be carried out at different granularities of a structured document with XML markups. This report aims at reviewing the state-of-the-arts in focused search, particularly techniques for topic-specific document retrieval, passage retrieval, XML retrieval, and entity ranking. It is concluded with highlight of open problems

The Role of Document Structure and Citation Analysis in Literature Information Retrieval

Literature Information Retrieval (IR) is the task of searching relevant publications given a particular information need expressed as a set of queries. With the staggering growth of scientific literature, it is critical to design effective retrieval solutions to facilitate efficient access to them. We hypothesize that particular genre specific characteristics of scientific literature such as metadata and citations are potentially helpful for enhancing scientific literature search. We conducted systematic and extensive IR experiments on open information retrieval test collections to investigate their roles in enhancing literature information retrieval effectiveness. This thesis consists of three major parts of studies. First, we examined the role of document structure in literature search through comprehensive studies on the retrieval effectiveness of a set of structure-aware retrieval models on ad hoc scientific literature search tasks. Second, under the language modeling retrieval framework, we studied exploiting citation and co-citation analysis results as sources of evidence for enhancing literature search. Specifically, we examined relevant document distribution patterns over partitioned clusters of document citation and co-citation graphs; we examined seven ways of modeling document prior probabilities of being relevant based on document citation and co-citation analysis; we studied the effectiveness of boosting retrieved documents with scores of their neighborhood documents in terms co-citation counts, co-citation similarities and Howard White's pennant scores. Third, we combined both structured retrieval features and citation related features in developing machine learned retrieval models for literatures search and assessed the effectiveness of learning to rank algorithms and various literature-specific features. Our major findings are as follows. State-of-the-art structure-ware retrieval models though reportedly perform well in known item finding tasks do not significantly outperform non-fielded baseline retrieval models in ad hoc literature information retrieval. Though relevant document distributions over citation and co-citation network graph partitions reveal favorable pattern, citation and co-citation analysis results on the current iSearch test collection only modestly improve retrieval effectiveness. However, priors derived from co-citation analysis outperform that derived from citation analysis, and pennant score for document expansion outperforms raw co-citation count or cosine similarity of co-citation counts. Our learning to rank experiments show that in a heterogeneous collection setting, citation related features can significantly outperform baselines.Ph.D., Information Studies -- Drexel University, 201

EveTAR: Building a Large-Scale Multi-Task Test Collection over Arabic Tweets

This article introduces a new language-independent approach for creating a large-scale high-quality test collection of tweets that supports multiple information retrieval (IR) tasks without running a shared-task campaign. The adopted approach (demonstrated over Arabic tweets) designs the collection around significant (i.e., popular) events, which enables the development of topics that represent frequent information needs of Twitter users for which rich content exists. That inherently facilitates the support of multiple tasks that generally revolve around events, namely event detection, ad-hoc search, timeline generation, and real-time summarization. The key highlights of the approach include diversifying the judgment pool via interactive search and multiple manually-crafted queries per topic, collecting high-quality annotations via crowd-workers for relevancy and in-house annotators for novelty, filtering out low-agreement topics and inaccessible tweets, and providing multiple subsets of the collection for better availability. Applying our methodology on Arabic tweets resulted in EveTAR , the first freely-available tweet test collection for multiple IR tasks. EveTAR includes a crawl of 355M Arabic tweets and covers 50 significant events for which about 62K tweets were judged with substantial average inter-annotator agreement (Kappa value of 0.71). We demonstrate the usability of EveTAR by evaluating existing algorithms in the respective tasks. Results indicate that the new collection can support reliable ranking of IR systems that is comparable to similar TREC collections, while providing strong baseline results for future studies over Arabic tweets