13867867
Outlier detection by sampling with accuracy guarantees
An effective approach to detecting anomalous points in a data setis distance-based outlier detection. This paper describes a simplesampling algorithm to effciently detect distance-based outliers indomains where each and every distance computation is veryexpensive. Unlike any existing algorithms, the sampling algorithmrequires a xed number of distance computations and can return goodresults with accuracy guarantees. The most computationallyexpensive aspect of estimating the accuracy of the result issorting all of the distances computed by the sampling algorithm.The experimental study on two expensive domains as well as tenadditional real-life datasets demonstrates both the effciency andeffectiveness of the sampling algorithm in comparison with thestate-of-the-art algorithm and there liability of the accuracyguarantees.
12268600
EITH - A Unifying Representation for Database Schema and Application Code in Enterprise Knowledge Extraction
The integration of heterogeneous legacy databases requires understanding of database structure and content. We previously developed a theoretical and software infrastructure to support the extraction of schema and business rule information from legacy sources, combining database reverse engineering with semantic analysis of associated application code (DRE/SA). In this paper, we present a compact formalism called EITH that unifies the representation of database schema and application code. EITH can be efficiently derived from various types of schema representations, particularly the relational model, and supports comparison of a wide variety of schema and code constructs to enable interoperation. Unlike UML or E/R diagrams, for example, EITH has compact notation, is unambiguous, and uses a small set of efficient heuristics. We show how EITH is employed in the context of SEEK, using a construction project management example. We also show how EITH can represent various structures in relational databases, and can serve as an efficient representation for E/R diagrams. This suggests that EITH can support efficient matching of more complex, hierarchical structures via indexed tree representations, without compromising the EITH design philosophy or formalism.
1744642
A Bayesian Method for Guessing the Extreme Values in a Data Set
For a large number of data management problems, it would be very useful to be able to obtain a few samples from a data set, and to use the samples to guess the largest (or smallest) value in the entire data set. Min/max online aggregation, top-k query processing, outlier detection, and distance join are just a few possible applications. This paper details a statistically rigorous, Bayesian approach to attacking this problem. Just as importantly, we demonstrate the utility of our approach by showing how it can be applied to two specific problems that arise in the context of data management.
968102
Do security toolbars actually prevent phishing attacks?
Security toolbars in a web browser show security-related information about a website to help users detect phishing attacks. Because the toolbars are designed for humans to use, they should be evaluated for usability -- that is, whether these toolbars really prevent users from being tricked into providing personal information. We conducted two user studies of three security toolbars and other browser security indicators and found them all ineffective at preventing phishing attacks. Even though subjects were asked to pay attention to the toolbar, many failed to look at it; others disregarded or explained away the toolbars' warnings if the content of web pages looked legitimate. We found that many subjects do not understand phishing attacks or realize how sophisticated such attacks can be.
16312232
An algorithm for wipe detection
The detection of transitions between shots in video programs is an important first step in analyzing video content. The wipe is a frequently used transitional form between shots. Wipe detection is more involved than the detection of abrupt and other gradual transitions because a wipe may take various patterns and because of the difficulty in discriminating a wipe from object and camera motion. In this paper, we propose an algorithm for detecting wipes using both structural and statistical information. The algorithm can effectively detect most wipes used in current TV programs. It uses the DC sequence which can be easily extracted from the MPEG stream without full decompression.
524265
A Direct Method for Building Sparse Kernel Learning Algorithms
Many kernel learning algorithms, including support vector machines, result in a kernel machine, such as a kernel classifier, whose key component is a weight vector in a feature space implicitly introduced by a positive definite kernel function. This weight vector is usually obtained by solving a convex optimization problem. Based on this fact we present a direct method to build sparse kernel learning algorithms by adding one more constraint to the original convex optimization problem, such that the sparseness of the resulting kernel machine is explicitly controlled while at the same time performance is kept as high as possible. A gradient based approach is provided to solve this modified optimization problem. Applying this method to the support vectom machine results in a concrete algorithm for building sparse large margin classifiers. These classifiers essentially find a discriminating subspace that can be spanned by a small number of vectors, and in this subspace, the different classes of data are linearly well separated. Experimental results over several classification benchmarks demonstrate the effectiveness of our approach.
39279084
Supporting Group-By and Pipelining in Bitmap-Enabled Query Processors
The Group-By operation is widely used in relational Data Warehouses for the aggregation and presentation of results according to user-defined criteria. Rearranging Group-By and join operations has been proposed as an optimization technique that reduces the size of the input relation. Pipelining is another optimization technique that promotes intra-query parallelism by transfering intermediate results to the next operation without materializing them. In Data Warehouses and environments in which exploratory on-line queries are common, pipelining can be used both for optimizing joins and for the reduction of response time by presenting partial results to the user. Efficient pipelining often depends on the order of the intermediate results. Order-dependent operations, such as Group-By, typically require the complete result set before ordering it, thereby making efficient pipelining impossible. In this paper we exploit bitmap indexing to implement Group-By in a manner that can be used for pipelining. Algorithms are presented for different assumptions about buffer availability and for different sort orders.
1384427
Classification-based spatial error concealment for images
This paper presents a new, classification-based spatial error concealment algorithm for images. The proposed scheme takes advantage of two state-of-the-art concealment schemes and adaptively selects a better suitable concealment scheme for each corrupted block. Using a support vector machine (SVM) classifier, our proposed approach outperforms the prior art in terms of the concealment quality and has moderate computational complexity.