Página 6 dos resultados de 23237 itens digitais encontrados em 0.032 segundos

Metadados para reconciliação de transações em bancos de dados autônomos; Metadata for transaction reconciliation in autonomous databases

Duarte, Gustavo Luiz
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/12/2011 PT
Relevância na Pesquisa
36.31%
O uso de técnicas de replicação de dados em dispositivos móveis permite que uma aplicação móvel compartilhe dados com um servidor e possa atuar sobre tais dados durante períodos de desconexão. Embora essa característica seja fundamental em diversos domínios, a reconciliação das transações que foram aplicadas sobre a réplica móvel dos dados apresenta-se como um desafio a ser superado. O uso de bloqueios apresenta-se impraticável em determinados domínios de aplicação. Por outro lado, ao permitir a execução de operações de escrita em diversas réplicas sem uma sincronização a priori, o sistema se torna suscetível a conflitos de atualização, sendo necessário a implementação de um mecanismo de resolução de conflitos. Resolver conflitos é uma tarefa complexa e propensa a erros, em especial nos casos em que há a necessidade de intervenção humana. Diante desse cenário, foi desenvolvido um modelo para controle de transações em bancos de dados autônomos que faz uso de metadados e multiversão de banco de dados de forma a permitir a auditoria e retificação de resoluções de conflitos. Isso torna a resolução de conflitos uma operação não destrutiva, reduzindo, assim, o impacto de uma resolução de conflito incorreta. Neste trabalho é apresentado também um arcabouço para reconciliação de transações que implementa o modelo proposto. Como estudo de caso...

Um modelo de evolução de esquemas conceituais para bancos de dados orientados a objetos com o emprego de versões; A schema evolution model for object-oriented databases with versions

Galante, Renata de Matos
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.31%
Aplicações ditas não convencionais, como, por exemplo, CAD, CASE, Automação de Escritórios, entre outras, freqüentemente exigem a manutenção de diversos estados da base de dados, retendo o histórico das modificações realizadas. Como resposta a tal requisito, é empregado o conceito de Versão. Neste trabalho o Modelo de Versões proposto por Golendziner é empregado no contexto da evolução de esquemas. Versões são utilizadas para armazenar os diferentes estados do esquema, de suas classes e métodos e, ainda, para posterior adaptação das instancias vigentes no banco de dados, mantendo um histórico da evolução do esquema do banco de dados. É proposto um modelo flexível de suporte a evolução de esquemas em bancos de dados orientados a objetos, bem como estratégias de propagação das instancias vigentes na base de dados. O histórico das modificações é representado pela derivação de versões do esquema e de seus elementos. Os estados anteriores as transformações são preservados, permitindo aos usuários a navegação retroativa e proativa entre versões, para realização de operações consistentes de modificação e consulta.; Non-conventional applications such as CAD, CASE, office automation often require the maintenance of various database states...

Online data mining services for dynamic spatial databases II: air quality location based services and sonification

Teixeira, Luís; Barbosa, Álvaro; Cardoso, Jorge C. S.; Carvalhos, Vasco; Costa, Manuel; Sousa, Inês; Franco, Ivan; Fonseca, Alexandra; Henriques, Diana; Rosa, Paulo
Fonte: Universidade Católica Portuguesa Publicador: Universidade Católica Portuguesa
Tipo: Artigo de Revista Científica
Publicado em //2005 ENG
Relevância na Pesquisa
36.31%
This paper introduces online data mining services for dynamic spatial databases associated with environmental monitoring networks. In particular, it describes an application that uses these services with sonification for air quality location based information services to the general public. The data mining services use Artificial Neural Networks, to find temporal relations in the monitored parameters. The execution of the algorithms performed at the server side and a distributed processing scheme is used to overcome problems of scalability. In addition, two other families of web services are made available to support the discovery of temporal relations: vectorial and raster map? services and a sonification service. The map services were implemented in DM Plus, a client application presented in part I. The sonification service is described in this paper and illustrated through an application study that implements an air quality index with sonification for mobile phones.

Discovery of Convoys in Trajectory Databases

Jeung, Hoyoung; Yiu, Man Lung; Zhou, Xiaofang; Jensen, Christian S.; Shen, Heng Tao
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/02/2010
Relevância na Pesquisa
36.41%
As mobile devices with positioning capabilities continue to proliferate, data management for so-called trajectory databases that capture the historical movements of populations of moving objects becomes important. This paper considers the querying of such databases for convoys, a convoy being a group of objects that have traveled together for some time. More specifically, this paper formalizes the concept of a convoy query using density-based notions, in order to capture groups of arbitrary extents and shapes. Convoy discovery is relevant for real-life applications in throughput planning of trucks and carpooling of vehicles. Although there has been extensive research on trajectories in the literature, none of this can be applied to retrieve correctly exact convoy result sets. Motivated by this, we develop three efficient algorithms for convoy discovery that adopt the well-known filter-refinement framework. In the filter step, we apply line-simplification techniques on the trajectories and establish distance bounds between the simplified trajectories. This permits efficient convoy discovery over the simplified trajectories without missing any actual convoys. In the refinement step, the candidate convoys are further processed to obtain the actual convoys. Our comprehensive empirical study offers insight into the properties of the paper's proposals and demonstrates that the proposals are effective and efficient on real-world trajectory data.

Mragyati : A System for Keyword-based Searching in Databases

Sarda, N. L.; Jain, Ankur
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/10/2001
Relevância na Pesquisa
36.41%
The web, through many search engine sites, has popularized the keyword-based search paradigm, where a user can specify a string of keywords and expect to retrieve relevant documents, possibly ranked by their relevance to the query. Since a lot of information is stored in databases (and not as HTML documents), it is important to provide a similar search paradigm for databases, where users can query a database without knowing the database schema and database query languages such as SQL. In this paper, we propose such a database search system, which accepts a free-form query as a collection of keywords, translates it into queries on the database using the database metadata, and presents query results in a well-structured and browsable form. Th eysytem maps keywords onto the database schema and uses inter-relationships (i.e., data semantics) among the referred tables to generate meaningful query results. We also describe our prototype for database search, called Mragyati. Th eapproach proposed here is scalable, as it does not build an in-memory graph of the entire database for searching for relationships among the objects selected by the user's query.

Inductive Logic Programming in Databases: from Datalog to DL+log

Lisi, Francesca A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/03/2010
Relevância na Pesquisa
36.41%
In this paper we address an issue that has been brought to the attention of the database community with the advent of the Semantic Web, i.e. the issue of how ontologies (and semantics conveyed by them) can help solving typical database problems, through a better understanding of KR aspects related to databases. In particular, we investigate this issue from the ILP perspective by considering two database problems, (i) the definition of views and (ii) the definition of constraints, for a database whose schema is represented also by means of an ontology. Both can be reformulated as ILP problems and can benefit from the expressive and deductive power of the KR framework DL+log. We illustrate the application scenarios by means of examples. Keywords: Inductive Logic Programming, Relational Databases, Ontologies, Description Logics, Hybrid Knowledge Representation and Reasoning Systems. Note: To appear in Theory and Practice of Logic Programming (TPLP).; Comment: 30 pages, 3 figures, 2 tables.

Aggregation and Ordering in Factorised Databases

Bakibayev, Nurzhan; Kočiský, Tomáš; Olteanu, Dan; Závodný, Jakub
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/07/2013
Relevância na Pesquisa
36.41%
A common approach to data analysis involves understanding and manipulating succinct representations of data. In earlier work, we put forward a succinct representation system for relational data called factorised databases and reported on the main-memory query engine FDB for select-project-join queries on such databases. In this paper, we extend FDB to support a larger class of practical queries with aggregates and ordering. This requires novel optimisation and evaluation techniques. We show how factorisation coupled with partial aggregation can effectively reduce the number of operations needed for query evaluation. We also show how factorisations of query results can support enumeration of tuples in desired orders as efficiently as listing them from the unfactorised, sorted results. We experimentally observe that FDB can outperform off-the-shelf relational engines by orders of magnitude.; Comment: 12 pages, 8 figures

Making massive probabilistic databases practical

Todor, Andrei; Dobra, Alin; Kahveci, Tamer; Dudley, Christopher
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/07/2013
Relevância na Pesquisa
36.41%
Existence of incomplete and imprecise data has moved the database paradigm from deterministic to proba- babilistic information. Probabilistic databases contain tuples that may or may not exist with some probability. As a result, the number of possible deterministic database instances that can be observed from a probabilistic database grows exponentially with the number of probabilistic tuples. In this paper, we consider the problem of answering both aggregate and non-aggregate queries on massive probabilistic databases. We adopt the tuple independence model, in which each tuple is assigned a probability value. We develop a method that exploits Probability Generating Functions (PGF) to answer such queries efficiently. Our method maintains a polynomial for each tuple. It incrementally builds a master polynomial that expresses the distribution of the possible result values precisely. We also develop an approximation method that finds the distribution of the result value with negligible errors. Our experiments suggest that our methods are orders of magnitude faster than the most recent systems that answer such queries, including MayBMS and SPROUT. In our experiments, we were able to scale up to several terabytes of data on TPC- H queries...

Conditioning Probabilistic Databases

Koch, Christoph; Olteanu, Dan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.41%
Past research on probabilistic databases has studied the problem of answering queries on a static database. Application scenarios of probabilistic databases however often involve the conditioning of a database using additional information in the form of new evidence. The conditioning problem is thus to transform a probabilistic database of priors into a posterior probabilistic database which is materialized for subsequent query processing or further refinement. It turns out that the conditioning problem is closely related to the problem of computing exact tuple confidence values. It is known that exact confidence computation is an NP-hard problem. This has led researchers to consider approximation techniques for confidence computation. However, neither conditioning nor exact confidence computation can be solved using such techniques. In this paper we present efficient techniques for both problems. We study several problem decomposition methods and heuristics that are based on the most successful search techniques from constraint satisfaction, such as the Davis-Putnam algorithm. We complement this with a thorough experimental evaluation of the algorithms proposed. Our experiments show that our exact algorithms scale well to realistic database sizes and can in some scenarios compete with the most efficient previous approximation algorithms.; Comment: 13 pages...

A Spatial Data Model for Moving Object Databases

Hajari, Hadi; Hakimpour, Farshad
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/03/2014
Relevância na Pesquisa
36.41%
Moving Object Databases will have significant role in Geospatial Information Systems as they allow users to model continuous movements of entities in the databases and perform spatio-temporal analysis. For representing and querying moving objects, and algebra with a comprehensive framework of User Defined Types together with a set of functions on those types is needed. Moreover, concerning real world applications, moving objects move along constrained environments like transportation networks so that an extra algebra for modeling networks is demanded, too. These algebras can be inserted in any data model if their designs are based on available standards such as Open Geospatial Consortium that provides a common model for existing DBMS's. In this paper, we focus on extending a spatial data model for constrained moving objects. Static and moving geometries in our model are based on Open Geospatial Consortium standards. We also extend Structured Query Language for retrieving, querying, and manipulating spatio-temporal data related to moving objects as a simple and expressive query language. Finally as a proof of concept, we implement a generator to generate data for moving objects constrained by a transportation network. Such a generator primarily aims at traffic planning applications.; Comment: This paper includes 20 pages and is published in IJDMS

Associative Arrays: Unified Mathematics for Spreadsheets, Databases, Matrices, and Graphs

Kepner, Jeremy; Chaidez, Julian; Gadepally, Vijay; Jansen, Hayden
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/01/2015
Relevância na Pesquisa
36.41%
Data processing systems impose multiple views on data as it is processed by the system. These views include spreadsheets, databases, matrices, and graphs. The common theme amongst these views is the need to store and operate on data as whole sets instead of as individual data elements. This work describes a common mathematical representation of these data sets (associative arrays) that applies across a wide range of applications and technologies. Associative arrays unify and simplify these different approaches for representing and manipulating data into common two-dimensional view of data. Specifically, associative arrays (1) reduce the effort required to pass data between steps in a data processing system, (2) allow steps to be interchanged with full confidence that the results will be unchanged, and (3) make it possible to recognize when steps can be simplified or eliminated. Most database system naturally support associative arrays via their tabular interfaces. The D4M implementation of associative arrays uses this feature to provide a common interface across SQL, NoSQL, and NewSQL databases.; Comment: 4 pages, 6 figures; New England Database Summit 2015

Probabilistic Databases with MarkoViews

Jha, Abhay; Suciu, Dan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/07/2012
Relevância na Pesquisa
36.41%
Most of the work on query evaluation in probabilistic databases has focused on the simple tuple-independent data model, where tuples are independent random events. Several efficient query evaluation techniques exists in this setting, such as safe plans, algorithms based on OBDDs, tree-decomposition and a variety of approximation algorithms. However, complex data analytics tasks often require complex correlations, and query evaluation then is significantly more expensive, or more restrictive. In this paper, we propose MVDB as a framework both for representing complex correlations and for efficient query evaluation. An MVDB specifies correlations by views, called MarkoViews, on the probabilistic relations and declaring the weights of the view's outputs. An MVDB is a (very large) Markov Logic Network. We make two sets of contributions. First, we show that query evaluation on an MVDB is equivalent to evaluating a Union of Conjunctive Query(UCQ) over a tuple-independent database. The translation is exact (thus allowing the techniques developed for tuple independent databases to be carried over to MVDB), yet it is novel and quite non-obvious (some resulting probabilities may be negative!). This translation in itself though may not lead to much gain since the translated query gets complicated as we try to capture more correlations. Our second contribution is to propose a new query evaluation strategy that exploits offline compilation to speed up online query evaluation. Here we utilize and extend our prior work on compilation of UCQ. We validate experimentally our techniques on a large probabilistic database with MarkoViews inferred from the DBLP data.; Comment: VLDB2012

A case study of the difficulty of quantifier elimination in constraint databases: the alibi query in moving object databases

Kuijpers, Bart; Othman, Walied; Grimson, Rafael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/12/2007
Relevância na Pesquisa
36.41%
In the constraint database model, spatial and spatio-temporal data are stored by boolean combinations of polynomial equalities and inequalities over the real numbers. The relational calculus augmented with polynomial constraints is the standard first-order query language for constraint databases. Although the expressive power of this query language has been studied extensively, the difficulty of the efficient evaluation of queries, usually involving some form of quantifier elimination, has received considerably less attention. The inefficiency of existing quantifier-elimination software and the intrinsic difficulty of quantifier elimination have proven to be a bottle-neck for for real-world implementations of constraint database systems. In this paper, we focus on a particular query, called the \emph{alibi query}, that asks whether two moving objects whose positions are known at certain moments in time, could have possibly met, given certain speed constraints. This query can be seen as a constraint database query and its evaluation relies on the elimination of a block of three existential quantifiers. Implementations of general purpose elimination algorithms are in the specific case, for practical purposes, too slow in answering the alibi query and fail completely in the parametric case. The main contribution of this paper is an analytical solution to the parametric alibi query...

Relational Semantics for Databases and Predicate Calculus

Kelly, Philip; van Emden, M. H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.41%
The relational data model requires a theory of relations in which tuples are not only many-sorted, but can also have indexes that are not necessarily numerical. In this paper we develop such a theory and define operations on relations that are adequate for database use. The operations are similar to those of Codd's relational algebra, but differ in being based on a mathematically adequate theory of relations. The semantics of predicate calculus, being oriented toward the concept of satisfiability, is not suitable for relational databases. We develop an alternative semantics that assigns relations as meaning to formulas with free variables. This semantics makes the classical predicate calculus suitable as a query language for relational databases.; Comment: 18 pages, 8 figures. arXiv admin note: text overlap with arXiv:cs/0607039

A Storage Advisor for Hybrid-Store Databases

Rösch, Philipp; Dannecker, Lars; Hackenbroich, Gregor; Faerber, Franz
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/08/2012
Relevância na Pesquisa
36.41%
With the SAP HANA database, SAP offers a high-performance in-memory hybrid-store database. Hybrid-store databases---that is, databases supporting row- and column-oriented data management---are getting more and more prominent. While the columnar management offers high-performance capabilities for analyzing large quantities of data, the row-oriented store can handle transactional point queries as well as inserts and updates more efficiently. To effectively take advantage of both stores at the same time the novel question whether to store the given data row- or column-oriented arises. We tackle this problem with a storage advisor tool that supports database administrators at this decision. Our proposed storage advisor recommends the optimal store based on data and query characteristics; its core is a cost model to estimate and compare query execution times for the different stores. Besides a per-table decision, our tool also considers to horizontally and vertically partition the data and manage the partitions on different stores. We evaluated the storage advisor for the use in the SAP HANA database; we show the recommendation quality as well as the benefit of having the data in the optimal store with respect to increased query performance.; Comment: VLDB2012

Dissociation and Propagation for Efficient Query Evaluation over Probabilistic Databases

Gatterbauer, Wolfgang; Suciu, Dan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.41%
Probabilistic inference over large data sets is an increasingly important data management challenge. The central problem is that exact inference is generally #P-hard, which limits the size of data that can be efficiently queried. This paper proposes a new approach for approximate evaluation of queries over probabilistic databases: in this approach, every query is evaluated entirely in the database engine by evaluating a fixed number of query plans, each providing an upper bound on the true probability, then taking their minimum. We provide an algorithm that takes into account important schema information to enumerate only the minimal necessary plans among all possible plans. Importantly, this algorithm is a strict generalization of all known results of PTIME self-join free conjunctive queries: the query is safe if and only if our algorithm returns one single plan. Furthermore, our approach is a generalization of a family of efficient network ranking functions from graphs to hypergraphs. We also describe three relational query optimization techniques that allow us to evaluate all minimal safe plans in a single query and very fast. We give a detailed experimental evaluation of our approach and, in the process, provide new way of thinking about the value of probabilistic methods over non-probabilistic methods for ranking query answers. We also note that the techniques developed in this paper apply immediately to lifted inference from statistical relational models since lifted inference corresponds to safe plans in probabilistic databases.; Comment: 29 pages...

Simple databases to monitor the generation and organisation of transgenic mouse colonies

Montoliu, Lluís
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 116384 bytes; application/pdf
ENG
Relevância na Pesquisa
36.41%
3 pages, 1 figure.-- PMID: 12739892 [PubMed].; The generation and analysis of transgenic mice has become an important tool to progress our understanding of human and mouse gene function and its association with human genetic diseases. Animal models, based on genetically modified mice, both standard transgenic and knock-out animals, are increasingly being used world-wide. Monitoring of transgenic mouse production and transgenic mouse colonies is required to efficiently manage the resources that are available. Here, I describe three independent FileMaker databases (transgenics, mymouse and cages) that have been developed to track the generation of transgenic mice, the organisation of transgenic mouse colonies and the distribution of mice in cages. These three databases are freely available for academic use.; This work was supported by funds from Spanish Ministry of Science and Technology Bio97-0628, Bio2000-1653, FEDER 2FD1997-2059, and Laboratorios Dr. Esteve S.A.; Peer reviewed

Avaliação psicológica: análise das publicações disponíveis na SciELO e BVS-Psi; Psychological assessment: analysis of publications in the databases SciELO and Bvs-Psi

Barroso, Sabrina Martins; Universidade Federal do Triângulo Mineiro
Fonte: Eduff Publicador: Eduff
Tipo: ; ; ; Avaliado por pares; metaciência; revivão de literatura Formato: application/pdf
Publicado em 01/05/2010 PT
Relevância na Pesquisa
36.41%
 O objetivo do presente trabalho foi analisar a produção nacional de artigos relacionados à avaliação psicológica. Realizou-se uma busca nas bases de dados SCIELO e BVS-PSI, utilizando-se as palavras-chave avaliação psicológica, testes psicológicos e testagem psicológica. Foram selecionados 333 trabalhos, nos quais foram analisadas as categorias divulgação, discurso, temática, autoria e metodologia. Os resultados indicaram aumento nas publicações sobre o tema nos últimos anos, dificuldades para localizar artigos nas bases virtuais, predominância de trabalhos de natureza empírica, relacionados ao estudo dos instrumentos, especialmente dos testes psicológicos e maioria de artigos de autoria única e feminina. Palavras-chave: metaciência, avaliação psicológica; testes psicológicos; testagem psicológica; bases de dados virtuais.; The objective of this study was to analyze the article production related to psychological assessment. It was realized a search in electronic databases SciELO and BVS-Psi, using the keywords psychological assessment, psychological tests and psychological testing. 333 articles were selected, and were analyzed in the categories divulgation, speech, topics, authors and methodology. The results showed an increase in scientific production in recent years...

Towards the Bioassay Activity Landscape Modeling in Compound Databases

Medina-Franco,José Luis; Waddell,Jacob
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
36.41%
Public compound databases annotated with biological activity are increasingly being used in drug discovery programs. A prominent example is of such databases is PubChem. Herein, we introduce an approach to systematically characterize the structure-bioassay activity relationships in PubChem using the concept of bioassay activity landscape. This strategy is general and can be applied to any data set screened across multiple bioassays. We also present a visual representation of the chemical space of an in-house data set using a recently developed web-based public tool.

Anonymizing but Deteriorating Location Databases

Khanh Dang,Tran; Anh Truong,Tuan
Fonte: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo Publicador: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
36.41%
The tremendous development of location-based services and mobile devices has led to an increase in location databases. Through the data mining process, valuable information can be discovered from such location databases. However, the malicious data miner or attackers may also extract private and sensitive information about the user, and this can create threats against the user location privacy. Therefore, location privacy protection becomes a key factor to the success in privacy protection for the users of location-based services. In this paper, we propose a novel approach as well as an algorithm to guarantee k-anonymity in a location database. The algorithm will maintain the association rules that have significance for the data mining process. Moreover, there may appear new significant association rules created after anonymization, they maybe affect the data mining result. Therefore, the algorithm also considers excluding new significant association rules that are created during the run of the algorithm. Theoretical analyses and experimental results with real-world datasets will confirm the practical value of our newly proposed approach.