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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Núcleo gerenciador de objetos compatibilizando eficiência e flexibilidade / A core object manager balancing flexibility and eficiency

Valêncio, Carlos Roberto 06 September 2000 (has links)
A tecnologia de construção de Sistemas de Gerenciamento de Base de Dados tradicionais, em particular dos que suportam o Modelo Relacional, tem atendido às exigências das aplicações na área de negócios ao longo dos anos. No entanto, aplicações mais complexas, tais como projetos de Engenharia e manufatura (CAD, CAM e CIM1), experimentos científicos, suporte à Medicina, telecomunicações, sistemas de informação geográfica e sistemas multimídia, têm exigido recursos mais sofisticados, para os quais os atuais sistemas gerenciadores de base de dados não foram concebidos e, portanto, têm encontrado dificuldades em atender. Com o objetivo de disponibilizar novas tecnologias para o gerenciamento de dados não convencionais, esse trabalho descreve um Núcleo Gerenciador de Objetos que oferece um conjunto de recursos para suporte flexível e eficiente às atividades de gerenciamento de dados. Esse gerenciador é apresentado no contexto de um modelo de dados orientado a objetos, porém a maioria dos conceitos e soluções apresentadas podem ser aproveitadas em outros tipos de gerenciadores de dados, independentemente do modelo de dados suportado. Em particular, o núcleo pode ser utilizado tanto para a implementação de um gerenciador de dados orientados a objetos quanto para um gerenciador relacional. O núcleo prevê também sua utilização como gerenciadores de dados que suportem a manipulação de dados fracamente estruturados (ou semi-estruturados) e como gerenciador de documentos multimídia em aplicações centradas na Web. A implementação do Núcleo Gerenciador de Objetos foi executada de maneira modular numa arquitetura em camadas, que delimitam a implementação das funcionalidades oferecidas. Apesar da forte integração entre as diversas camadas, necessária para a operação eficiente dos gerenciadores de dados, essa arquitetura provê uma definição precisa dos diversos módulos, permitindo que mais de uma alternativa de implementação possa existir para cada módulo, tornando o sistema resultante altamente configurável. Dentre os principais tópicos para os quais esse trabalho apresenta contribuições inovadoras encontram-se: o gerenciamento de identificadores de objetos (Oids); gerenciamento de transação e controle de concorrência baseado na semântica da aplicação; otimização de acessos ao disco para execução de operações de modificação de registros dentro de transações; uso de estruturas de tuplas e listas concorrentemente, para agilizar o acesso e a definição dos atributos de objetos; e a manutenção de esquemas e dados integrados numa mesma estrutura. / The technologies employed to build the current generation of Database Management Systems - DBMS, including those based on the Relational Model have been enough to support the needs of traditional business application. However, more demanding applications, like computer-aided design and manufacturing (CAD, CAM and CIM), scientific data retrieval and analysis, computer aided medical systems, telecommunications, geographical information systems and multimedia systems yet have not been adequately supported. The objective of this work is to develop new technologies to build DBMSs that support those non-conventional applications. To this intend, we implemented an object manager kernel, incorporating a representative set of tools able to provide a flexible and efficient support for key DBMSs operations. The kernel is described based on an object-oriented manager. However almost every new techniques proposed can be used together with data managers supporting other data models. In particular, we show that this kernel can be used to build both Object-oriented and Relational DBMSs. The kernel also supports the construction of DBMSs that maintain loosely-structured data (or semi-structured data), providing a good starting point to build web-based applications to handle multimedia documents. The kernel was implemented in a modular, multi-level architecture. Each module provides a well-defined service, and has a well defined interface, so it is possible to have more than one implementation for each module, enabling the comparison or tuning of the kernel for each specific situations. Nonetheless, the structure enforces a tight module integration, enabling the efficient execution of the resulting DBMS. The main contributions of this work include new techniques to improve the following aspects of database managers: Object Identifier management - OIds; transaction and concurrency control based on the application data semantic; disk accesses optimization to manage page shadowing during transaction execution; use of attribute tuples and lists to define structures; and integrated schema and data storage into a common structure.
42

Modularização de produto e os efeitos sobre a eficiência técnica: uma avaliação em uma fabricante de ônibus

Piran, Fabio Antonio Sartori 30 June 2015 (has links)
Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-10-19T18:24:54Z No. of bitstreams: 1 FABIO ANTONIO SARTORI PIRAN_.pdf: 4177497 bytes, checksum: 92bd3c20cfdca3446ffa85184e18d87f (MD5) / Made available in DSpace on 2015-10-19T18:24:54Z (GMT). No. of bitstreams: 1 FABIO ANTONIO SARTORI PIRAN_.pdf: 4177497 bytes, checksum: 92bd3c20cfdca3446ffa85184e18d87f (MD5) Previous issue date: 2015-06-30 / Nenhuma / A melhoria da eficiência e da produtividade tem atraído um interesse crescente das empresas, e a modularização é considerada uma alternativa estratégica para atingir essas finalidades. No entanto, apesar de a pesquisa sobre modularização apontar esses e outros benefícios, evidências empíricas que suportam essas expectativas são escassas na literatura. Portanto, é necessário avaliar os efeitos que a modularização produz para contribuir para a melhoria da eficiência de uma área ou de um sistema produtivo, por exemplo. Este estudo analisa os efeitos da implementação da modularização de produtos sobre a eficiência da Engenharia de Produtos e do Processo Produtivo em uma empresa fabricante de ônibus. Esses efeitos foram avaliados longitudinalmente utilizando, combinadamente, a Análise Envoltória de Dados, a Análise de Variância (ANOVA) e a Avaliação do Impacto Causal em Séries Temporais (CausalImpact) em um estudo de caso. Como resultados, evidencia-se que os efeitos da modularização sobre a eficiência são positivos e significativos. Observa-se, também, diferenças significativas entre projetos e produtos modularizados e não modularizados. Por fim, a pesquisa estabelece e suporta empiricamente a causalidade entre a modularização e a eficiência da Engenharia de Produtos e do Processo Produtivo da empresa analisada. / The improvement of efficiency and productivity has attracted a growing interest by companies, and the modularization is considered a strategic alternative to achieve this purpose. However, despite the research on modularization points to this and other benefits, the empirical evidence supporting such expectations is scarce in the literature. Therefore, it is necessary to evaluate the effects the modularization produces in order to contribute to the improvement of the efficiency of an area or a productive system, for instance. The present study analyzes the effects of the implementation of product modularization over the efficiency of a company that manufactures buses. These effects were evaluated longitudinally using, in a combined way, the Data Envelopment Analysis, the Variance Analysis (ANOVA), and the Evaluation of the Causal Impact in Time Series (CausalImpact) on a study case. As a result, we can see that the effects of modularization on the efficiency are positive and significant. We also can note significant differences between modularized and non-modularized projects and products. Finally, this research establishes and empirically support the causality between modularization and the efficiency of Product Engineering in the productive process of the company studied.
43

Customization Through Standardization : a study on Atlas Copco Tools & Assembly Systems’ market offer of fixtured tools to the motor vehicle industry

Cramér, Martin, Matsson, Anders January 2004 (has links)
<p>Atlas Copco Tools & Assembly Systems (ACTA) is world leader in industrial tools and assembly systems for safety-critical joints. One of the products the company sells is fixtured nutrunners, mainly to the motor vehicle industry. The margins on these highly customized products have been decreasing – much depending on changes in the purchasing behavior of the automotive industry.</p><p>Traditionally, the marketing of the fixtured nutrunners has been concentrated to the parts of the product instead of the final product. Today, there is a belief within the organization that many of the sold customized products could be replaced by more standardized applications. There is also a wish to turn the focus of the market offer from the parts towards the final application. These beliefs and wishes resulted in this thesis, with the purpose to propose a new market offer to increase profitability and give more customer benefits.</p><p>To reach this purpose we started out with theoretical studies of several different areas. Among those was mass customization, a strategy that combines the benefits of mass production with those of customization. We also performed a prestudy at the headquarters of ACTA in Sickla and visited major customers in Sweden. Using our collected knowledge from the theoretical studies and the prestudy, we conducted an in-depth case study by interviewing customers and people working at ACTA, both in Sweden and in the USA, in order to analyze today’s situation. In the analysis, we found several problems with today’s offer. For instance, we found that similar products are solved with unique solutions, which has lead to poor cost control and has made it difficult for ACTA to assure the quality of the ordered products. A further problem is the poor sales support and the lack of traceability of sold systems, which reduces sales and leads to unnecessary special solutions. A problem linked to that is the difficulties in getting accurate and sufficient information from the customer, which leads to extra errors and a lot of extra work.</p><p>To solve these problems, we recommend ACTA to implement a mass customization strategy. Of course, not all of ACTA’s products can be mass customized, but to a large extent it should be possible. To implement a mass customization strategy, we argue that ACTA should take three measures, namely design standard products, modularize the products, and implement a computerized configuration tool. We also suggest that the implementation of the new market offer should be done stepwise. With the proposed new market offer, we believe that ACTA can increase profitability in the area of fixtured nutrunners without losing the flexibility of the products.</p>
44

A generic information platform for product families

Sivard, Gunilla January 2001 (has links)
The research work detailed in this dissertation relates to the computer representation of information which concerns product families and product platforms. Common to competitive companies today, is the quest of designing products and processes to meet a large variety of customer needs, in short time, and based on few resources. One way to succeed with this endeavor is to plan for the variety and design a modular, or adaptive, product family based on a common platform of resources. To further increase the efficiency in delivering customized products in time, a computer processible model of the family is created, which is used to realize a customer specific product variant during the order phase. The objective of this research is to define a generally applicable model of product family information for the purpose of supporting various applications, and for achieving an efficient utilization of information. The approach is to define a model of the product family according to the theory of Axiomatic Design, which reflects the trace from various requirements to functions and different properties and components of the product. By representing information from design in a generally applicable format, this information can be reused when building the configuration models of the order phase. By adapting the model to an existing standard, information exchange between systems is supported, and access is provided to information concerning detailed physical parts as well as constructs addressing various use and version management. Contributions include a description of a model architecture with reusable functional solutions, interfaces, structures and interrelations between platform solutions and product family. Further, it is described how to extend and model the domains and interrelations of axiomatic design in an information model, which is adapted to the product modeling standard of ISO10303-214. / QC 20100812
45

Customization Through Standardization : a study on Atlas Copco Tools &amp; Assembly Systems’ market offer of fixtured tools to the motor vehicle industry

Cramér, Martin, Matsson, Anders January 2004 (has links)
Atlas Copco Tools &amp; Assembly Systems (ACTA) is world leader in industrial tools and assembly systems for safety-critical joints. One of the products the company sells is fixtured nutrunners, mainly to the motor vehicle industry. The margins on these highly customized products have been decreasing – much depending on changes in the purchasing behavior of the automotive industry. Traditionally, the marketing of the fixtured nutrunners has been concentrated to the parts of the product instead of the final product. Today, there is a belief within the organization that many of the sold customized products could be replaced by more standardized applications. There is also a wish to turn the focus of the market offer from the parts towards the final application. These beliefs and wishes resulted in this thesis, with the purpose to propose a new market offer to increase profitability and give more customer benefits. To reach this purpose we started out with theoretical studies of several different areas. Among those was mass customization, a strategy that combines the benefits of mass production with those of customization. We also performed a prestudy at the headquarters of ACTA in Sickla and visited major customers in Sweden. Using our collected knowledge from the theoretical studies and the prestudy, we conducted an in-depth case study by interviewing customers and people working at ACTA, both in Sweden and in the USA, in order to analyze today’s situation. In the analysis, we found several problems with today’s offer. For instance, we found that similar products are solved with unique solutions, which has lead to poor cost control and has made it difficult for ACTA to assure the quality of the ordered products. A further problem is the poor sales support and the lack of traceability of sold systems, which reduces sales and leads to unnecessary special solutions. A problem linked to that is the difficulties in getting accurate and sufficient information from the customer, which leads to extra errors and a lot of extra work. To solve these problems, we recommend ACTA to implement a mass customization strategy. Of course, not all of ACTA’s products can be mass customized, but to a large extent it should be possible. To implement a mass customization strategy, we argue that ACTA should take three measures, namely design standard products, modularize the products, and implement a computerized configuration tool. We also suggest that the implementation of the new market offer should be done stepwise. With the proposed new market offer, we believe that ACTA can increase profitability in the area of fixtured nutrunners without losing the flexibility of the products.
46

A Lightweight Framework for Universal Fragment Composition

Henriksson, Jakob 06 January 2009 (has links) (PDF)
Domain-specific languages (DSLs) are useful tools for coping with complexity in software development. DSLs provide developers with appropriate constructs for specifying and solving the problems they are faced with. While the exact definition of DSLs can vary, they can roughly be divided into two categories: embedded and non-embedded. Embedded DSLs (E-DSLs) are integrated into general-purpose host languages (e.g. Java), while non-embedded DSLs (NE-DSLs) are standalone languages with their own tooling (e.g. compilers or interpreters). NE-DSLs can for example be found on the Semantic Web where they are used for querying or describing shared domain models (ontologies). A common theme with DSLs is naturally their support of focused expressive power. However, in many cases they do not support non–domain-specific component-oriented constructs that can be useful for developers. Such constructs are standard in general-purpose languages (procedures, methods, packages, libraries etc.). While E-DSLs have access to such constructs via their host languages, NE-DSLs do not have this opportunity. Instead, to support such notions, each of these languages have to be extended and their tooling updated accordingly. Such modifications can be costly and must be done individually for each language. A solution method for one language cannot easily be reused for another. There currently exist no appropriate technology for tackling this problem in a general manner. Apart from identifying the need for a general approach to address this issue, we extend existing composition technology to provide a language-inclusive solution. We build upon fragment-based composition techniques and make them applicable to arbitrary (context-free) languages. We call this process for the composition techniques’ universalization. The techniques are called fragment-based since their view of components— reusable software units with interfaces—are pieces of source code that conform to an underlying (context-free) language grammar. The universalization process is grammar-driven: given a base language grammar and a description of the compositional needs wrt. the composition techniques, an adapted grammar is created that corresponds to the specified needs. The result is thus an adapted grammar that forms the foundation for allowing to define and compose the desired fragments. We further build upon this grammar-driven universalization approach to allow developers to define the non–domain-specific component-oriented constructs that are needed for NE-DSLs. Developers are able to define both what those constructs should be, and how they are to be interpreted (via composition). Thus, developers can effectively define language extensions and their semantics. This solution is presented in a framework that can be reused for different languages, even if their notion of ‘components’ differ. To demonstrate the approach and show its applicability, we apply it to two Semantic Web related NE-DSLs that are in need of component-oriented constructs. We introduce modules to the rule-based Web query language Xcerpt and role models to the Web Ontology Language OWL.
47

Ontology Based Framework for Conceptualizing Human Affective States and Their Influences

Abaalkhail, Rana 12 November 2018 (has links)
The study of human affective states and their influences has been a research interest in psychology for some time. Fortunately, the presence of an affective computing paradigm allows us to use theories and findings from the discipline of psychology in the representation and development of human affective applications. However, because of the complexity of the subject, it is possible to misunderstand concepts that are shared via human and/or computer communications. With the appearance of technological innovations in our lives, for instance the SemanticWeb and the Web Ontology Language (OWL), there is a stronger need for computers to better understand human affective states and their influences. The use of an ontology can be beneficial in order to represent human affective states and their influences in a machine-understandable format. Truly, ontologies provide powerful tools to make sense of data. Our thesis proposes HASIO, a Human Affective States and their Influences Ontology, designed based on existing psychological theories. HASIO was developed to represent the knowledge that is necessary to model affective states and their influences in a computerized format. It describes the human affective states (Emotion, Mood and Sentiment) and their influences (Personality, Need and Subjective well-being) and conceptualizes their models and recognition methods. HASIO also represents the relationships between affective states and the factors that influence them. We surveyed and analyzed existing ontologies regarding human affective states and their influences to realize the significance and profit of developing our proposed ontology (HASIO). We follow the Methontology approach, a comprehensive engineering methodology for ontology building, to design and build HASIO. An important aspect in determining the ontology scope is Competency Questions (CQs). We configure HASIO CQs by analyzing the resources from psychology theories, available lexicons and existing ontologies. In this thesis, we present the development, modularization and evaluation of HASIO. HASIO can profit from the modularization process by dividing the whole ontology in self-contained modules that are easy to reuse and maintain. The ontology is evaluated through Question Answering system (HASIOQA), a task-based evaluation system, for validation. We design and develop a natural language interface system for this purpose. Moreover, the proposed ontology was evaluated through the Ontology Pitfall Scanner for verification and correctness against several criteria. Furthermore, HASIO was used in sentiment analysis on diffrent Twitter dataset. We designed and developed a tweet polarity calculation algorithm. Additionally, we compare our ontology result with machine learning technique. We demonstrate and highlight the advantage of using ontology in sentiment analysis.
48

Objektorientierte Modularisierung von Maschinen im Kontext zu I40

Schmertosch, Thomas 30 May 2018 (has links) (PDF)
Eine Herausforderung aus Industrie 4.0 ist die Produktion individueller Produkte in der Losgröße 1. Dabei denken wir zuerst an Fotobuch, die Cola mit einem Etikett, das unseren Namen trägt und viele weitere der inzwischen zahlreich angebotenen individualisierten Endprodukte. Dabei wird oft vergessen, dass für deren Herstellung Maschinen und Anlagen erforderlich sind, die selbst individuelle Produkte sind und nicht mehr kosten sollen als deren Pendants aus der Großserie. Um dies zu leisten, reicht es nicht aus, Daten in einer Cloud zu sammeln und auszuwerten oder das Förderband mit einem Internetanschluss zu versehen. Vielmehr bedarf es ganzheitlicher Konzepte, mit denen Produktionssysteme nachhaltig und individuell entwickelt werden können. Ein Lösungsansatz dazu ist die funktions- und objektorientierte Modularisierung, bei der die zu realisierenden Funktionen den gesamten Entwicklungs- und Konstruktionsprozess bestimmen. [... aus dem Text]
49

Uma abordagem para apoio à decisão de refatoração em sistemas de software / Class-splitting refactoring based on temporal analysis of cohesion

Machado, João Paulo Lemes 28 August 2017 (has links)
A falta de modularização é um dos principais problemas encontrados em sistemas de software. Diversos estudos abordam esse problema apresentando soluções que visam aumentar a qualidade da modularização. Contudo, ainda não existe uma solução definitiva que possa ser aplicada em qualquer situação na qual esse problema ocorre. Uma situação específica diz respeito à falta de coesão entre os métodos de uma classe em sistemas orientados a objetos. Para essa situação, uma solução apropriada seria aplicar a refatoração de classes. O processo de refatoração de classes tem como objetivo melhorar a modularização de um sistema sem altear suas funcionalidades. Contudo, esse processo pode ser extremamente complexo e difícil de ser executado, pois existem efeitos colaterais que podem ser provocados por alterações indevidas. Nesse contexto, ainda existe uma lacuna por melhores sistemas de apoio à refatoração visando o aumento de coesão entre métodos das classes e uma melhor modularização do sistema. Assim, este trabalho tem como objetivo propor uma abordagem para fornecer informações de apoio à refatoração. Tais informações foram obtidas a partir de uma análise dos impactos gerados pelas refatorações aplicadas em 8 sistemas desenvolvidos na linguagem Java. O impacto dessas refatorações foram identificados e medidos através da análise da evolução das métricas de coesão. Foi realizada uma análise qualitativa sobre as refatorações identificadas com o objetivo de determinar qual tipo de estratégia foi adotada em cada situação. A partir dessa análise foi possível propor guias de refatoração que foram apresentadas aos desenvolvedores dos 8 sistemas através de um survey. O estudo obteve resultados positivos onde a partir de discussões realizadas com os desenvolvedores foram observadas situações nas quais as guias propostas claramente ajudariam no processo de refatoração. Também foram constatadas situações nas quais as recomendações podem ser adotadas como novas práticas com o objetivo de evitar perdas de modularização. / The lack of modularization is one of the main problems encountered in software systems. Several studies address this problem by presenting solutions that aim to increase the modularization quality. However, there is still no definitive solution that can be applied in any situation in which this problem occurs. A specific situation concerns the lack of cohesion among methods of a class in object-oriented systems. In this situation, an appropriate solution would be to apply a class refactoring. The class refactoring process aims at improving the modularization of a system without changing its functionalities. However, this process can be complex and difficult to execute because of the side effects that can be caused by improper changes. In this context, better systems for supporting refactoring are still lacking, so the cohesion between class methods and a better modularization of the system could be achieved. This work proposes an approach to provide information to support of refactoring. This information was obtained from an analysis of the impacts generated by the refactorings applied in 8 systems developed in Java language. The impact of these refactorings was identified and measured by analyzing the evolution of cohesion metrics. A qualitative analysis was performed on the refactorings identified with the objective of determining what type of strategy was adopted in each situation. From this analysis it was possible to propose refactoring guides that were presented to the developers of the 8 systems through a survey. The study found positive results in which discussions with the developers led to situations in which the proposed guidelines would clearly help the refactoring process. It was also observed situations in which the recommendations can be adopted as new practices in order to avoid losses of modularization. / Dissertação (Mestrado)
50

Núcleo gerenciador de objetos compatibilizando eficiência e flexibilidade / A core object manager balancing flexibility and eficiency

Carlos Roberto Valêncio 06 September 2000 (has links)
A tecnologia de construção de Sistemas de Gerenciamento de Base de Dados tradicionais, em particular dos que suportam o Modelo Relacional, tem atendido às exigências das aplicações na área de negócios ao longo dos anos. No entanto, aplicações mais complexas, tais como projetos de Engenharia e manufatura (CAD, CAM e CIM1), experimentos científicos, suporte à Medicina, telecomunicações, sistemas de informação geográfica e sistemas multimídia, têm exigido recursos mais sofisticados, para os quais os atuais sistemas gerenciadores de base de dados não foram concebidos e, portanto, têm encontrado dificuldades em atender. Com o objetivo de disponibilizar novas tecnologias para o gerenciamento de dados não convencionais, esse trabalho descreve um Núcleo Gerenciador de Objetos que oferece um conjunto de recursos para suporte flexível e eficiente às atividades de gerenciamento de dados. Esse gerenciador é apresentado no contexto de um modelo de dados orientado a objetos, porém a maioria dos conceitos e soluções apresentadas podem ser aproveitadas em outros tipos de gerenciadores de dados, independentemente do modelo de dados suportado. Em particular, o núcleo pode ser utilizado tanto para a implementação de um gerenciador de dados orientados a objetos quanto para um gerenciador relacional. O núcleo prevê também sua utilização como gerenciadores de dados que suportem a manipulação de dados fracamente estruturados (ou semi-estruturados) e como gerenciador de documentos multimídia em aplicações centradas na Web. A implementação do Núcleo Gerenciador de Objetos foi executada de maneira modular numa arquitetura em camadas, que delimitam a implementação das funcionalidades oferecidas. Apesar da forte integração entre as diversas camadas, necessária para a operação eficiente dos gerenciadores de dados, essa arquitetura provê uma definição precisa dos diversos módulos, permitindo que mais de uma alternativa de implementação possa existir para cada módulo, tornando o sistema resultante altamente configurável. Dentre os principais tópicos para os quais esse trabalho apresenta contribuições inovadoras encontram-se: o gerenciamento de identificadores de objetos (Oids); gerenciamento de transação e controle de concorrência baseado na semântica da aplicação; otimização de acessos ao disco para execução de operações de modificação de registros dentro de transações; uso de estruturas de tuplas e listas concorrentemente, para agilizar o acesso e a definição dos atributos de objetos; e a manutenção de esquemas e dados integrados numa mesma estrutura. / The technologies employed to build the current generation of Database Management Systems - DBMS, including those based on the Relational Model have been enough to support the needs of traditional business application. However, more demanding applications, like computer-aided design and manufacturing (CAD, CAM and CIM), scientific data retrieval and analysis, computer aided medical systems, telecommunications, geographical information systems and multimedia systems yet have not been adequately supported. The objective of this work is to develop new technologies to build DBMSs that support those non-conventional applications. To this intend, we implemented an object manager kernel, incorporating a representative set of tools able to provide a flexible and efficient support for key DBMSs operations. The kernel is described based on an object-oriented manager. However almost every new techniques proposed can be used together with data managers supporting other data models. In particular, we show that this kernel can be used to build both Object-oriented and Relational DBMSs. The kernel also supports the construction of DBMSs that maintain loosely-structured data (or semi-structured data), providing a good starting point to build web-based applications to handle multimedia documents. The kernel was implemented in a modular, multi-level architecture. Each module provides a well-defined service, and has a well defined interface, so it is possible to have more than one implementation for each module, enabling the comparison or tuning of the kernel for each specific situations. Nonetheless, the structure enforces a tight module integration, enabling the efficient execution of the resulting DBMS. The main contributions of this work include new techniques to improve the following aspects of database managers: Object Identifier management - OIds; transaction and concurrency control based on the application data semantic; disk accesses optimization to manage page shadowing during transaction execution; use of attribute tuples and lists to define structures; and integrated schema and data storage into a common structure.

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