abstract: Skyline queries extract interesting points that are non-dominated and help paint the bigger picture of the data in question. They are valuable in many multi-criteria decision applications and are becoming a staple of decision support systems. An assumption commonly made by many skyline algorithms is that a skyline query is applied to a single static data source or data stream. Unfortunately, this assumption does not hold in many applications in which a skyline query may involve attributes belonging to multiple data sources and requires a join operation to be performed before the skyline can be produced. Recently, various skyline-join algorithms have been proposed to address this problem in the context of static data sources. However, these algorithms suffer from several drawbacks: they often need to scan the data sources exhaustively to obtain the skyline-join results; moreover, the pruning techniques employed to eliminate tuples are largely based on expensive tuple-to-tuple comparisons. On the other hand, most data stream techniques focus on single stream skyline queries, thus rendering them unsuitable for skyline-join queries. Another assumption typically made by most of the earlier skyline algorithms is that the data is complete and all skyline attribute values are available. Due to this constraint, these algorithms cannot be applied to incomplete data sources in which some of the attribute values are missing and are represented by NULL values. There exists a definition of dominance for incomplete data, but this leads to undesirable consequences such as non-transitive and cyclic dominance relations both of which are detrimental to skyline processing. Based on the aforementioned observations, the main goal of the research described in this dissertation is the design and development of a framework of skyline operators that effectively handles three distinct types of skyline queries: 1) skyline-join queries on static data sources, 2) skyline-window-join queries over data streams, and 3) strata-skyline queries on incomplete datasets. This dissertation presents the unique challenges posed by these skyline queries and addresses the shortcomings of current skyline techniques by proposing efficient methods to tackle the added overhead in processing skyline queries on static data sources, data streams, and incomplete datasets. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2014

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2017-10-05T20:06:57Z No. of bitstreams: 2 Dissertacao- Welder Batista de Oliveira - 2017.pdf: 2420889 bytes, checksum: c26aee2605e42f2a9aecb9ec2523464f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-06T11:09:11Z (GMT) No. of bitstreams: 2 Dissertacao- Welder Batista de Oliveira - 2017.pdf: 2420889 bytes, checksum: c26aee2605e42f2a9aecb9ec2523464f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-10-06T11:09:11Z (GMT). No. of bitstreams: 2 Dissertacao- Welder Batista de Oliveira - 2017.pdf: 2420889 bytes, checksum: c26aee2605e42f2a9aecb9ec2523464f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-21 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Geographic Information Systems have revolutionized geographic research over the past three decades. These systems commonly provide a number of features for processing andanalyzing spatial data, such as spatial join and skyline. Although relevant, the effectiveness of such functionalities is affected by the imprecision of the geographic coordinates obtained by the georeferencing method employed. Moreover, the error contained in the coordinates may present several distributional patterns, which demands the development of solutions that are generalist concerning the error pattern that they can handle properly. Finally, spatial operations are already computationally expensive in their deterministic version, which is aggravated by the introduction of the stochastic component. The pre-sent work presents a general structure of spatial operations solutions robust to imprecise coordinates based on the use of simulations and probabilistic adaptations of heuristics in the literature. In addition, to deal with the problems mentioned, the proposed structure is designed to contemplate the requirements of generality, accuracy and efficiency at levels that enable its practical application. The overall solution structure is composed of the combination of probabilistic versions of heuristics of the deterministic versions of the spatial operations and by Monte Carlo simulations. From that structure, specific solutions - as case studies - are developed for the spatial join and skyline. Theoretical and experimental results demonstrated the potential of the developed solutions to meet the threerequirements established in this work. / Os Sistemas de Informação Geográfica revolucionaram a pesquisa geográfica nas últimas três décadas. Esses sistemas comumente disponibilizam uma série de funcionalidades para processar e analisar dados espaciais, como, por exemplo, a junção espacial e a consulta skyline. Embora relevantes, a eficácia dessas funcionalidades é impactada pela imprecisão das coordenadas geográficas obtidas pelo método de georreferenciamento empregado. Além disso, o erro contido nas coordenadas pode apresentar diversos padrões distribucionais, o que demanda o desenvolvimento de soluções que sejam generalistas quanto ao padrão de erro que conseguem tratar adequadamente. Por fim, operações espaciais já são computacionalmente caras em sua versão determinística, o que se agrava com a introdução do componente estocástico. O presente trabalho apresenta uma estrutura geral para o desenvolvimento de soluções para operações espaciais robustas a coordenadas imprecisas. Além disso, para lidar com os problemas mencionados, a estrutura proposta é projetada para contemplar os requisitos de generalidade, eficácia e eficiência em patamares que viabilizem sua aplicação prática. A estrutura geral de solução é composta pela combinação de versões probabilísticas de heurísticas das versões determinísticas das operações espaciais e por simulações de Monte Carlo. A partir dela, são desenvolvidas as soluções específicas – como estudo de caso - para a skyline espacial e da junção espacial. Resultados teóricos e experimentais demonstraram o potencial das soluções desenvolvidas em atender aos três requisitos estabelecidos nesse trabalho.

Top-k and Skyline queries are a long study topic in database and information retrieval communities and they are two popular operations for preference retrieval. Top-k query returns a subset of the most relevant answers instead of all answers. Efficient top-k processing retrieves the k objects that have the highest overall score. In this paper, some algorithms that are used as a technique for efficient top-k processing for different scenarios have been represented. A framework based on existing algorithms with considering based cost optimization that works for these scenarios has been presented. This framework will be used when the user can determine the user ranking function. A real life scenario has been applied on this framework step by step. Skyline query returns a set of points that are not dominated (a record x dominates another record y if x is as good as y in all attributes and strictly better in at least one attribute) by other points in the given datasets. In this paper, some algorithms that are used for evaluating the skyline query have been introduced. One of the problems in the skyline query which is called curse of dimensionality has been presented. A new strategy that based on the skyline existing algorithms, skyline frequency and the binary tree strategy which gives a good solution for this problem has been presented. This new strategy will be used when the user cannot determine the user ranking function. A real life scenario is presented which apply this strategy step by step. Finally, the advantages of the top-k query have been applied on the skyline query in order to have a quickly and efficient retrieving results.