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Published methods for distributed information retrieval generally rely on cooperation from search servers. But most real servers, particularly the tens of thousands available on the Web, are not engineered for such cooperation. This means that the majority of methods proposed, and evaluated in simulated environments of homogeneous cooperating servers, are never applied in practice. ¶ This thesis introduces new methods for server selection and results merging. The methods do not require search servers to cooperate, yet are as effective as the best methods which do. Two large experiments evaluate the new methods against many previously published methods. In contrast to previous experiments they simulate a Web-like environment, where servers employ varied retrieval algorithms and tend not to sub-partition documents from a single source. ¶ The server selection experiment uses pages from 956 real Web servers, three different retrieval systems and TREC ad hoc topics. Results show that a broker using queries to sample servers’ documents can perform selection over non-cooperating servers without loss of effectiveness. However, using the same queries to estimate the effectiveness of servers, in order to favour servers with high quality retrieval systems, did not consistently improve selection effectiveness. ¶ The results merging experiment uses documents from five TREC sub-collections, five different retrieval systems and TREC ad hoc topics. Results show that a broker using a reference set of collection statistics, rather than relying on cooperation to collate true statistics, can perform merging without loss of effectiveness. Since application of the reference statistics method requires that the broker download the documents to be merged, experiments were also conducted on effective merging based on partial documents. The new ranking method developed was not highly effective on partial documents, but showed some promise on fully downloaded documents. ¶ Using the new methods, an effective search broker can be built, capable of addressing any given set of available search servers, without their cooperation.

Federated information retrieval is a technique for searching multiple text collections simultaneously. Queries are submitted to a subset of collections that are most likely to return relevant answers. The results returned by selected collections are integrated and merged into a single list. Federated search is preferred over centralized search alternatives in many environments. For example, commercial search engines such as Google cannot index uncrawlable hidden web collections; federated information retrieval systems can search the contents of hidden web collections without crawling. In enterprise environments, where each organization maintains an independent search engine, federated search techniques can provide parallel search over multiple collections. There are three major challenges in federated search. For each query, a subset of collections that are most likely to return relevant documents are selected. This creates the collection selection problem. To be able to select suitable collections, federated information retrieval systems acquire some knowledge about the contents of each collection, creating the collection representation problem. The results returned from the selected collections are merged before the final presentation to the user. This final step is the result merging problem. In this thesis, we propose new approaches for each of these problems. Our suggested methods, for collection representation, collection selection, and result merging, outperform state-of-the-art techniques in most cases. We also propose novel methods for estimating the number of documents in collections, and for pruning unnecessary information from collection representations sets. Although management of document duplication has been cited as one of the major problems in federated search, prior research in this area often assumes that collections are free of overlap. We investigate the effectiveness of federated search on overlapped collections, and propose new methods for maximizing the number of distinct relevant documents in the final merged results. In summary, this thesis introduces several new contributions to the field of federated information retrieval, including practical solutions to some historically unsolved problems in federated search, such as document duplication management. We test our techniques on multiple testbeds that simulate both hidden web and enterprise search environments.

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This research advances distributed information sharing by equipping nodes (e.g., software agents) in a distributed network with (1) partner selection algorithms in cooperative environments, and (2) strategies for providing and requesting information in competitive environments. In cooperative environments, information providers are willing to provide requested information, but information consumers must consider uncertainty in the quality of provided information when selecting appropriate information providers. In competitive environments, if a self-interested agent can be an information consumer and provider at the same time, agents need to determine the best ways to request and provide information so that the information acquisition utility can be maximized. This research defines a set of metrics for evaluating information acquisition utility, and presents a game-theoretic approach for determining the best information sharing strategies based on stochastic games. The results show how agents build collaborative relationships with appropriate agents and how the information acquisition utility is affected by those relationships. / text

<p>This thesis suggests a security evaluation framework for distributed information systems, responsible for generating a system modelling technique and an evaluation method. The framework is flexible and divides the problem space into smaller, more accomplishable subtasks with the means to focus on specific problems, aspects or system scopes. The information system is modelled by dividing it into increasingly smaller parts, evaluate the separate parts and then build up the system “bottom up” by combining the components. Evaluated components are stored as reusable instances in a component library. The evaluation method is focusing on technological components and is based on the Security Functional Requirements (SFR) of the Common Criteria. The method consists of the following steps: (1) define several security values with different aspects, to get variable evaluations (2) change and establish the set of SFR to fit the thesis, (3) interpret evaluated security functions, and possibly translate them to CIA or PDR, (4) map characteristics from system components to SFR and (5) combine evaluated components into an evaluated subsystem. An ontology is used to, in a versatile and dynamic way, structure the taxonomy and relations of the system components, the security functions, the security values and the risk handling. It is also a step towards defining a common terminology for IT security.</p>

Mobile agent planning (MAP) is increasingly viewed as an important technique of information retrieval systems to provide location aware services of minimum cost in mobile computing environment. Although Hopfield-Tank neural network has been proposed for solving the traveling salesperson problem, little attention has been paid to the time constraints on resource validity for optimizing the cost of the mobile agent. Consequently, we hypothesized that Hopfield-Tank neural network can be used to solve the MAP problem. To test this hypothesis, we modify Hopfield-Tank neural network and design a new energy function to not only cope with the dynamic temporal features of the computing environment, in particular the server performance and network latency when scheduling mobile agents, but also satisfy the location-based constraints such as the starting and end node of the routing sequence must be the home site of the traveling mobile agent. In addition, the energy function is reformulated into a Lyapunov function to guarantee the convergent stable state and existence of the valid solution. The connection weights between the neurons and the activation function of state variables in the dynamic network are devised in searching for the valid solutions. Moreover, the objective function is derived to estimate the completion time of the valid solutions and predict the optimal routing path. Simulations study was conducted to evaluate the proposed model and algorithm for different time variables and various coefficient values of the energy function. The experimental results quantitatively demonstrate the computational power and speed of the proposed model by producing solutions that are very close to the minimum costs of the location-based and time-constrained distributed MAP problem rapidly. The spatio-temporal technique proposed in this work is an innovative approach in providing knowledge applicable to improving the effectiveness of solving optimization problems.

<p>This thesis suggests a set of system characteristics to be used when evaluating or analyzing the IT security of a distributed information system. Each characteristic is meant to be considered in the evaluation of relevant distributed system components. This is considered to be the first step towards finding a technique for modeling and evaluating the security of a system. The work also includes a definition of distributed information system components and a categorization of the found characteristics. The means used to identify the set of characteristics include a thorough investigation of the literature on the relevant subject, as well as a brainstorming session. Thereafter the material has been structured to form the results presented in this thesis.</p>

Orientador: Sueli Yoshinaga Pereira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-11T00:46:58Z (GMT). No. of bitstreams: 1 Penteado_AntonioHenriqueDantasdaGama_D.pdf: 2937340 bytes, checksum: 0d1fdfb079fad03ce60bc155ef48f8d4 (MD5) Previous issue date: 2006 / Resumo: Este trabalho tem por finalidade apresentar um protótipo de sistema de informação arquitetado e desenvolvido para auxiliar a gestão dos recursos hídricos no Estado de São Paulo. Esse sistema de informação para controle de outorgas e fiscalização, chamado de SICOF, foi desenhado para manter uma base de dados com informações sobre usuários e diferentes usos de recursos hídricos, e desenvolvido para amparar o Departamento de Águas e Energia Elétrica (DAEE) do Estado de São Paulo em algumas de suas funções administrativas básicas. O DAEE é o órgão competente para contemplar os usuários de recursos hídricos com o direito de uso da água. Para essa obrigação, adota como base a Portaria DAEE no 717/96. Essa portaria disciplina a forma e o conteúdo a ser apresentado ao DAEE no ato de solicitação do direito de uso por parte de um usuário, e foi empregada como padrão para o desenvolvimento do SICOF. Esse protótipo foi desenvolvido com as tecnologias Microsoft JavaScript, JScript e ASP, e estruturado para operar bancos de dados em redes fechadas ou internet. Foram utilizados: o padrão de modelagem de software chamado UML (Unified Modeling Language); o conceito de estruturação de sistemas em camadas; e o conceito de sistemas distribuídos via internet. As bases de dados foram desenvolvidas com o Microsoft ACCESS e são operadas por de linhas de programação. A opção pelas ferramentas acima mencionadas foi feita na busca de se produzir uma solução para atender ao aspecto descentralizador das políticas paulista e brasileira de recursos hídricos (Lei no 7.663/91 ¿ São Paulo; Lei Federal no 7.663/97), com baixo custo operacional e de implantação, elevado potencial de integralização dos dados e facilidade de operação. Sua arquitetura foi desmembrada em diferentes subsistemas que estão disponíveis ao seu operador: a) USUARIOS ¿ para dados de usuários, pessoas físicas ou jurídicas, de seus domicílios válidos; b) IMPLANTAR ¿para cadastrar resumidamente os diferentes usos de recursos hídricos, localização geográfica e valores de uso e consumo; c) AUTOS ¿ que relaciona solicitações de direto de uso aos números de processos e às respectivas certificações de direito de uso; d) UNIFILAR ¿ para pesquisa orientada por bacia hidrográfica, cujo resultado é a consolidação das ocorrências existentes em bacias hidrográficas informadas pelos usuários do sistema; e) SIPP ¿ para cadastramento técnico de poços perfurados. Tem como funções básicas: 1) adquirir informações via páginas e aplicativos internet; 2) armazenar informações em bases de dados relacionais via objetos de conectividade de base de dados; 3) integrar informações provenientes de bases de dados independentes; 4) gerar registros, fichas, tabelas e relatórios em formatos ASCII, HTM ou XML. O SICOF também pode ser utilizado como alimentador de bases de dados, uma vez que os dados são uniformemente formatados e podem ser transferidos para outros sistemas que operam dados diversos e georeferenciados. Por ser estruturado em linguagem simples e aberta, esse protótipo pode ser adaptado para novas funções quando surgirem novas necessidades. Por ter sido modelado ante sua concepção, pode ser reescrito e editado em outras linguagens de programação. Por fim, representa uma progressão científica em termos de aplicação de tecnologias na busca de soluções de baixo custo para otimizar a gestão dos recursos hídricos no Estado de São Paulo / Abstract: The aim of this work is to present an information system prototype, which was planned and developed to help water resources management in São Paulo State, Brazil. This information system for water right-of-use control and inspection, named SICOF, was projected to maintain a database with information about water users and different water resources uses in delimited regions that are recognized as hydrographic basins. It was developed to support some basic administrative functions of the Department of Water and Electric Energy of São Paulo State (DAEE), which is the institution responsible for granting water right of use to water resources users. Formats for registering water right of use and water resources users, as well as for requiring water use licenses are adopted according to DAEE¿s Law #717/96, which was used as a guideline to develop the SICOF modeling system. SICOF was structured on the basis of the following Microsoft technologies: Java Script, JScript, Active Server Pages (ASP), and Internet Information Server (IIS). It was also programmed to operate databases through intranet or Internet systems. Databases were generated with Microsoft ACCESS, being handled by Microsoft OBDC object. As for SICOF architecture, it was planned using the Unified Modeling Language (UML) in association with concepts of 3-layered systems and distributed systems via Internet, and their basics functions are: 1) to acquire information through web pages and Internet applications; 2) to store information in relational databases by database connective objects; 3) to integrate information from independent databases; 4) to generate records, files, tables, and reports in ASCII, HTML, XML or other file formats. It was divided in into different subsystems that are available to the operator: a) USUARIOS ¿ for water resources users data, considering their valid address information; b) IMPLANTAR ¿ to summarily register information about different water resources uses, geographic position, and use and consume values; c) AUTOS ¿ relates each request of water right of use to a process number, as well as to its respective water use license; d) UNIFILAR ¿ for hydrographic basin-oriented research. Information provided by the system users will compose tables and forms related to a certain hydrographic basin; e) SIPP ¿ for registering technical information about drilled wells for groundwater. SICOF processes and formats data uniformly; therefore, it may be used to collect primary data and to feed database systems with geo-referenced information. The development of this system focused on two objectives: 1) to line up the decentralized policies to first objective, given by Law #7.663/91 (São Paulo State) and by Federal Law #9.433/97; 2) to create an open and friendly source architecture, using low cost tools. The developed system presented here has shown good functionality to treat an amount of data that refers to one decentralized institute of water resources management. It is composed of: i) a software with programs code, routines, scripts, and databases; ii) SICOF technical document, which can be used to guide future projects to develop software and systems for water resources management / Doutorado / Administração e Politica de Recursos Minerais / Doutor em Ciências