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Extensive work has recently been done on the evaluation of positive queries on probabilistic databases. The case of queries with negation has notoriously been left out, since it raises serious additional challenges to efficient query evaluation.
This paper presents a query evaluation technique for positive relational algebra queries with aggregates on a representation system for probabilistic data based on the algebraic structures of semiring and semimodule. The core of our evaluation technique is a procedure that compiles semimodule and semiring expressions into so-called decomposition trees, for… (More)
The IT Infrastructure Library (ITIL) is a set of best practices that are widely accepted for IT service management. Change management is a core ITIL process that oversees the handling of IT changes and ensures that all change requests are carefully prioritized and authorized, that business and technical impacts are understood, and that required resources… (More)
This article charts the tractability frontier of two classes of relational algebra queries in tuple-independent probabilistic databases. The first class consists of queries with join, projection, selection, and negation but without repeating relation symbols and union. The second class consists of quantified queries that express the following binary… (More)
NRC publications in the NUREG series, NRC regulations, and Title 10, Energy, in the Code of Federal Regulations may also be purchased from one of these two sources: 1. are updated periodically and may differ from the last printed version. Although references to material found on a Web site bear the date the material was accessed, the material available on… (More)
The mutagenicity of anthracene, anthraquinone, and four structurally similar compounds of each was evaluated in the Ames/Salmonella microsome assay. Anthraquinone was shown to be mutagenic for strains TA1537, TA1538, and TA98 in the absence of rat liver homogenate. The four anthraquinone derivatives tested were mutagenic for TA1537 exclusively. None of the… (More)
Chrysophanol and islandicin, two anthraquinones which are structurally related to emodin, were found to be frame-shift mutagens for Salmonella typhimurium strain TA 1537 after metabolic activation.
This paper investigates the problem of approximating conjunctive queries without self-joins on probabilistic databases by lower and upper bounds that can be computed more efficiently. We study this problem via an indirection: Given a propositional formula &phis;, find formulas in a more restricted language that are greatest lower bound and least upper… (More)
SPROUT² is a query answering system that allows users to ask structured queries over tables embedded in Web pages, over Google Fusion tables, and over uncertain tables that can be extracted from answers to Google Squared. At the core of this service lies SPROUT, a query engine for probabilistic databases. This demonstration allows users to compose and… (More)
This article describes an approximation algorithm for computing the probability of propositional formulas over discrete random variables. It incrementally refines lower and upper bounds on the probability of the formulas until the desired absolute or relative error guarantee is reached. This algorithm is used by the SPROUT query engine to approximate the… (More)