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.
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.
34246581
Query Incentive Networks
We formulate a model for query incentive networks, motivated by users seeking information or services that pose queries, together with incentives for answering them. This type of information-seeking process can be formulated as a game among the nodes in the network, and this game has a natural Nash equilibrium. 
 
How much incentive is needed in order to achieve a reasonable probability of obtaining an answer to a query? We study the size of query incentives as a function both of the rarity of the answer and the structure of the underlying network. This leads to natural questions related to strategic behavior in branching processes. Whereas the classically studied criticality of branching processes is centered around the region where the branching parameter is 1, we show in contrast that strategic interaction in incentive propagation exhibits critical behavior when the branching parameter is 2. 
 
This lecture is based on the paper [14] with Jon Kleinberg of Cornell University.
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.
15130102
Towards a Grid enabled system for multicomponent materials design
We are developing a portal for multicomponent materials design using Grid-enabled large-scale simulations. In this paper we report on our services based application architecture which allows integration of simulation software with Grid services to provide a Web-based computational laboratory for the modeling of Al-Cu-Mg-Si alloys. We examine user requirements and describe the design of our framework. Our architecture is implemented using existing middleware such as the Globus and Java CoG toolkits. An interesting feature of our design is the separation of the high-level specification of the materials modeling system from the implementation through the use of a markup language such as XML. We use markup languages with domain-specific extensions to specify (in architecture-independent form) rules and constraints that allow meaningful composition of simulation tasks and experimentally determined material properties. In addition, we use them to specify application code interfaces so that our simulation server can be dynamically reconfigured to include new software and constraints.