43859978
Encoding XML in Vector Spaces
We develop a framework for representing XML documents and queries in vector spaces and build indexes for processing text-centric semi-structured queries that support a proximity measure between XML documents. The idea of using vector spaces for XML retrieval is not new. In this paper we (i) unify prior approaches into a single framework; (ii) develop techniques to eliminate special purpose auxiliary computations (outside the vector space) used previously; (iii) give experimental evidence on benchmark queries that our approach is competitive in its retrieval quality and (iv) as an immediate consequence of the framework, are able to classify and cluster XML documents.
2844508
Visualizing tags over time
We consider the problem of visualizing the evolution of tags within the Flickr (flickr.com) online image sharing community. Any user of the Flickr service may append a tag to any photo in the system. Over the past year, users have on average added over a million tags each week. Understanding the evolution of these tags over time is therefore a challenging task. We present a new approach based on a characterization of the most interesting tags associated with a sliding interval of time. An animation provided via Flash in a web browser allows the user to observe and interact with the interesting tags as they evolve over time.New algorithms and data structures are required to support the efficient generation of this visualization. We combine a novel solution to an interval covering problem with extensions to previous work on score aggregation in order to create an efficient backend system capable of producing visualizations at arbitrary scales on this large dataset in real time.
14496529
Variable latent semantic indexing
Latent Semantic Indexing is a classical method to produce optimal low-rank approximations of a term-document matrix. However, in the context of a particular query distribution, the approximation thus produced need not be optimal. We propose VLSI, a new query-dependent (or "variable") low-rank approximation that minimizes approximation error for any specified query distribution. With this tool, it is possible to tailor the LSI technique to particular settings, often resulting in vastly improved approximations at much lower dimensionality. We validate this method via a series of experiments on classical corpora, showing that VLSI typically performs similarly to LSI with an order of magnitude fewer dimensions.
53245339
Randomized Algorithms
For many applications, a randomized algorithm is either the simplest or the fastest algorithm available, and sometimes both. This book introduces the basic concepts in the design and analysis of randomized algorithms. The first part of the text presents basic tools such as probability theory and probabilistic analysis that are frequently used in algorithmic applications. Algorithmic examples are also given to illustrate the use of each tool in a concrete setting. In the second part of the book, each chapter focuses on an important area to which randomized algorithms can be applied, providing a comprehensive and representative selection of the algorithms that might be used in each of these areas. Although written primarily as a text for advanced undergraduates and graduate students, this book should also prove invaluable as a reference for professionals and researchers.
25665502
Incentive networks
We propose a notion of incentive networks, modeling online settings in which multiple participants in a network help each other find information. Within this general setting, we study query incentive networks, a natural abstraction of question-answering systems with rewards for finding answers. We analyze strategic behavior in such networks and under a simple model of networks, show that the Nash equilibrium for participants' strategies exhibits an unexpected threshold phenomenon.
13408394
Structure and evolution of blogspace
A critical look at more than one million bloggers and the individual entries of some 25,000 blogs reveals blogger demographics, friendships, and activity patterns over time.
1173806
A Combinatorial Scheme for Developing Efficient Composite Solvers
Many fundamental problems in scientific computing have more than one solution method. It is not uncommon for alternative solution methods to represent different tradeoffs between solution cost and reliability. Furthermore, the performance of a solution method often depends on the numerical properties of the problem instance and thus can vary dramatically across application domains. In such situations, it is natural to consider the construction of a multi-method composite solver to potentially improve both the average performance and reliability. In this paper, we provide a combinatorial framework for developing such composite solvers. We provide analytical results for obtaining an optimal composite from a set of methods with normalized measures of performance and reliability. Our empirical results demonstrate the effectiveness of such optimal composites for solving large, sparse linear systems of equations.