Liadan O'Callaghan

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Some important classical mechanisms considered in Microeconomics and Game Theory require the solution of a difficult optimization problem. This is true of mechanisms for combinatorial auctions, which have in recent years assumed practical importance, and in particular of the gold standard for combinatorial auctions, the Generalized Vickrey Auction (GVA).(More)
The data stream model has recently attracted attention for its applicability to numerous types of data, including telephone records, web documents and clickstreams. For analysis of such data, the ability to process the data in a single pass, or a small number of passes, while using little memory, is crucial. We describe such a streaming algorithm that(More)
Streaming data analysis has recently attracted attention in numerous applications including telephone records, web documents and clickstreams. For such analysis, single-pass algorithms that consume a small amount of memory are critical. We describe such a streaming algorithm that e ectively clusters large data streams. We also provide empirical evidence of(More)
We study clustering problems in the streaming model, where the goal is to cluster a set of points by making one pass (or a few passes) over the data using a small amount of storage space. Our main result is a randomized algorithm for the <i>k</i>--Median problem which produces a constant factor approximation in one pass using storage space <i>O(k poly</i>(More)
Some important classical mechanisms considered in Microeconomics and Game Theory require the solution of a diicult optimization problem. This is true of mechanisms for combinatorial auctions, which have in recent years assumed practical importance, and in particular of the gold standard for combinatorial auctions, the Generalized Vickrey Auction (GVA).(More)
The sliding window model is useful for discounting stale data in data stream applications. In this model, data elements arrive continually and only the most recent <i>N</i> elements are used when answering queries. We present a novel technique for solving two important and related problems in the sliding window model---maintaining variance and maintaining a(More)
We give a sampling-based algorithm for the k-Median problem, with running time O(k $$(\frac{{k^2 }}{ \in } \log k)^2 $$ log $$(\frac{k}{ \in } \log k)$$ ), where k is the desired number of clusters and ∈ is a confidence parameter. This is the first k-Median algorithm with fully polynomial running time that is independent of n, the size of the data set. It(More)
Some important classical mechanisms considered in Microeconomics and Game Theory require the solution of a diÆcult optimization problem. This is true of mechanisms for combinatorial auctions, which have in recent years assumed practical importance, and in particular of the gold standard for combinatorial auctions, the Generalized Vickrey Auction (GVA).(More)
We consider the problem of estimating the length of a shortest path in a DAG whose edge lengths are known only approximately but can be determined exactly at a cost. Initially, each edge e is known only to lie within an interval [le; he]; the estimation algorithm can pay ce to nd the exact length of e. In particular, we study the problem of nding the(More)
Some important classical mechanisms considered in Microeconomics and Game Theory require the solution of a diÆcult optimization problem. This is true of mechanisms for combinatorial auctions, which have in recent years assumed practical importance, and in particular of the gold standard for combinatorial auctions, the Generalized Vickrey Auction (GVA).(More)