1,720,991 research outputs found
Compressed Web indexes
No full textWeb search engines use indexes to efficiently retrieve pages containing specified query terms, as well as pages linking to specified pages. The problem of compressed indexes that permit such fast retrieval has a long history. We consider the problem: assuming that the terms in (or links to) a page are generated from a probability distribution, how well compactly can we build such indexes that allow fast retrieval? Of particular interest is the case when the probability distribution is Zipfian (or a similar power law), since these are the distributions that arise on the web. We obtain sharp bounds on the space requirement of Boolean indexes for text documents that follow Zipf's law. In the process we develop a general technique that applies to any probability distribution, not necessarily a power law; this is the first analysis of compression in indexes under arbitrary distributions. Our bounds lead to quantitative versions of rules of thumb that are folklore in indexing. Our experiments on several document collections show that the distribution of terms appears to follow a double-Pareto law rather than Zipf's law. Despite widely varying sets of documents, the index sizes observed in the experiments conform well to our theoretical predictions. Copyright is held by the International World Wide Web Conference Committee (IW3C2)
The limits of popularity-based recommendations, and the role of social ties
Get PDFIn this paper we introduce a mathematical model that captures some of the salient features of recommender systems that are based on popularity and that try to exploit social ties among the users. We show that, under very general conditions, the market always converges to a steady state, for which we are able to give an explicit form. Thanks to this we can tell rather precisely how much a market is altered by a recommendation system, and determine the power of users to influence others. Our theoretical results are complemented by experiments with real world social networks showing that social graphs prevent large market distortions in spite of the presence of highly influential user
Solução de Data Warehouse para possibilitar a análise estratégica integrada e distribuída dos indicadores de desempenho (IDS) do Estado de SC
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.Os indicadores de desenvolvimento social, desenvolvidos pela Durb, visam oferecer uma visão da realidade local através da apresentação do desempenho social e econômico do município (mais desenvolvido e menos desenvolvido). No entanto, a simples apresentação dos indicadores, seja em forma de tabelas ou gráficos, não supre a necessidade de informação comparativa e estratégicamente apresentada. Este trabalho tem como objetivo utilizar tecnologias de sistemas de informações, data warehouse, data webhouse, geoprocessamento e classificação de informações com análise multivariada, com o objetivo de apresentar uma ferramenta de apoio à análise estratégica dos indicadores de desenvolvimento do estado de SC, para uso de políticos e da comunidade catarinense. São obtidos dados externos de organizações com Prefeitura, IBGE, Secretarias estaduais de educação, saúde, entre outros que passam por um pré processamento, processo este que gera uma base com os dados integrados e voltados ao mesmo assunto. Esta base de data warehouse é garimpada passando por processos de análise de similaridade, gerando uma base de conhecimento que gera informação estratégica, essencial ao à tomada de decisão de políticos e da população
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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