Ces dernières années ont vu un regain d’intérêt dans l’utilisation de données semi-structurées, grâce à la standardisation de formats d’échange de données sur le Web tels que XML et RDF. On notera en particulier le Linking Open Data Project qui comptait plus de 31 milliard de triplets RDF à la fin de l’année 2011. XML reste, pour sa part, l’un des formats de données privilégié de nombreuses bases de données de grandes tailles dont Uniprot, Open Government Initiative et Penn Treebank. <p><p>Cet accroissement du volume de données semi-structurées a suscité un intérêt croissant pour le développement de bases de données adaptées. Parmi les différentes approches proposées, on peut distinguer les approches relationnelles et les approches graphes, comme détaillé au Chapitre 3. Les premières visent à exploiter les moteurs de bases de données relationnelles existants, en y intégrant des techniques spécialisées. Les secondes voient les données semistructurées comme des graphes, c’est-à-dire un ensemble de noeuds liés entre eux par des arêtes étiquetées, dont elles exploitent la structure. L’une des techniques de ce domaine, connue sous le nom d’indexation structurelle, vise à résumer les graphes de données, de sorte à pouvoir identifier rapidement les données utiles au traitement d’une requête.<p><p>Les index structurels classiques sont construits sur base des notions de simulation et de bisimulation sur des graphes. Ces notions, qui sont d’usage dans de nombreux domaines tels que la vérification, la sécurité, et le stockage de données, sont des relations sur les noeuds des graphes. Fondamentalement, ces notions caractérisent le fait que deux noeuds partagent certaines caractéristiques telles qu’un même voisinage. <p><p>Bien que les approches graphes soient efficaces en pratique, elles présentent des limitations dans le cadre de RDF et son langage de requêtes SPARQL. Les étiquettes sont, dans cette optique, distinctes des noeuds du graphe .Dans le modèle décrit par RDF et supporté par SPARQL, les étiquettes et noeuds font néanmoins partie du même ensemble. C’est pourquoi, les approches graphes ne supportent qu’un sous-ensemble des requêtes SPARQL. Au contraire, les approches relationnelles sont fidèles au modèle RDF, et peuvent répondre au différentes requêtes SPARQL. <p><p>La question à laquelle nous souhaitons répondre dans cette thèse est de savoir si les approches relationnelles et graphes sont incompatible, ou s’il est possible de les combiner de manière avantageuse. En particulier, il serait souhaitable de pouvoir conserver la performance des approches graphe, et la généralité des approches relationnelles. Dans ce cadre, nous réalisons un index structurel adapté aux données relationnelles. <p><p>Nous nous basons sur une méthodologie décrite par Fletcher et ses coauteurs pour la conception d’index structurels. Cette méthodologie repose sur trois composants principaux. Un premier composant est une caractérisation dite structurelle du langage de requêtes à supporter. Il s’agit ici de pouvoir identifier les données qui sont retournées en même temps par n’importe quelle requête du langage aussi précisément que possible. Un second composant est un algorithme qui doit permettre de grouper efficacement les données qui sont retournées en même temps, d’après la caractérisation structurelle. Le troisième composant est l’index en tant que tel. Il s’agit d’une structure de données qui doit permettre d’identifier les groupes de données, générés par l’algorithme précédent pour répondre aux requêtes. <p><p>Dans un premier temps, il faut remarquer que le langage SPARQL pris dans sa totalité ne se prête pas à la réalisation d’index structurels efficaces. En effet, le fondement des requêtes SPARQL se situe dans l’expression de requêtes conjonctives. La caractérisation structurelle des requêtes conjonctives est connue, mais ne se prête pas à la construction d’algorithmes efficaces pour le groupement. Néanmoins, l’étude empirique des requêtes SPARQL posées en pratique que nous réalisons au Chapitre 5 montre que celles-ci sont principalement des requêtes conjonctives acycliques. Les requêtes conjonctives acycliques sont connues dans la littérature pour admettre des algorithmes d’évaluation efficaces. <p><p>Le premier composant de notre index structurel, introduit au Chapitre<p>6, est une caractérisation des requêtes conjonctives acycliques. Cette<p>caractérisation est faite en termes de guarded simulation. Pour les graphes la<p>notion de simulation est une version restreinte de la notion de bisimulation.<p>Similairement, nous introduisons la notion de guarded simulation comme une<p>restriction de la notion de guarded bisimulation, une extension connue de la<p>notion de bisimulation aux données relationelles. <p><p>Le Chapitre 7 offre un second composant de notre index structurel. Ce composant est une structure de données appelée guarded structural index qui supporte le traitement de requêtes conjonctives quelconques. Nous montrons que, couplé à la caractérisation structurelle précédente, cet index permet d’identifier de manière optimale les données utiles au traitement de requêtes conjonctives acycliques. <p><p>Le Chapitre 8 constitue le troisième composant de notre index structurel et propose des méthodes efficaces pour calculer la notion de guarded simulation. Notre algorithme consiste essentiellement en une transformation d’une base de données en un graphe particulier, sur lequel les notions de simulation et guarded simulation correspondent. Il devient alors possible de réutiliser les algorithmes existants pour calculer des relations de simulation. <p><p>Si les chapitres précédents définissent une base nécessaire pour un index structurel visant les données relationnelles, ils n’intègrent pas encore cet index dans le contexte d’un moteur de bases de données relationnelles. C’est ce que propose le Chapitre 9, en développant des méthodes qui permettent de prendre en compte l’index durant le traitement d’une requête SPARQL. Des résultats expérimentaux probants complètent cette étude. <p><p>Ce travail apporte donc une première réponse positive à la question de savoir s’il est possible de combiner de manière avantageuse les approches relationnelles et graphes de stockage de données RDF.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Object oriented databases have been gaining popularity over the years. Their ease of use and the advantages that they offer over relational databases have made them a popular choice amongst database administrators. Their use in previous years was restricted to business and administrative applications, but improvements in technology and the emergence of new, data-intensive applications has led to the increase in the use of object databases. This study investigates four Open Source object-oriented databases on their ability to carry out the standard database operations of storing, querying, updating and deleting database objects. Each of these databases will be timed in order to measure which is capable of performing a particular function faster than the other.

This dissertation considers the use of a virtual machine as an access control mechanism in a relational database management system. Such a mechanism may prove to be more flexible than the normal access control mechanism that forms part of a relational database management system. The background information provided in this text (required to clearly comprehend the issues that are related to the virtual machine and its language) introduces databases, security and security mechanisms in relational database management systems. Finally, an existing implementation of a virtual machine that is used as a pseudo access control mechanism is provided. This mechanism is used to examine data that travels across a electronic communications network. Subsequently, the language of the virtual machine is chiefly considered, since it is this language which will determine the power and flexibility that the virtual machine offers. The capabilities of the language is illustrated by showing how it can be used to implement selected access control policies. Furthermore it is shown that the language can be used to access data stored in relations in a safe manner, and that the addition of the programs to the DAC model does not cause a significant increase in the management of a decentralised access control model. Following the proposed language it is obvious that the architecture of the ìnewî access control subsystem is also important since this architecture determines where the virtual machine fits in to the access control mechanism as a whole. Other extensions to the access control subsystem which are important for the functioning of the new access control subsystem are also reected upon. Finally, before concluding, the dissertation aims to provide general considerations that have to be taken into account for any potential implementation of the virtual machine. Aspects such as the runtime support system, data types and capabilities for extensions are taken into consideration. By examining all of the previous aspects, the access control language and programs, the virtual machine and the extensions to the access control subsystem, it is shown that the virtual machine and the language offered in this text provides the capability of implementing all the basic access control policies that can normally be provided. Additionally it can equip the database administrator with a tool to implement even more complex policies which can not be handled in a simple manner by the normal access control system. Additionally it is shown that using the virtual machine does not mean that certain complex policies have to be implemented on an application level. It is also shown that the new and extended access control subsystem does not significantly alter the way in which access control is managed in a relational database management system. / Prof. M.S. Olivier

Bancos de dados relacionais são fontes de dados rigidamente estruturadas, caracterizadas por relacionamentos complexos entre um conjunto de relações (tabelas). Entender tais relacionamentos é um desafio, porque os usuários precisam considerar múltiplas relações, entender restrições de integridade, interpretar vários atributos, e construir consultas SQL para cada tentativa de exploração. Neste cenário, introduz-se uma metodologia em duas etapas; primeiro utiliza-se um grafo organizado como uma estrutura hierárquica para modelar os relacionamentos do banco de dados, e então, propõe-se uma nova técnica de visualização para exploração relacional. Os resultados demonstram que a proposta torna a exploração de bases de dados significativamente simplificada, pois o usuário pode navegar visualmente pelos dados com pouco ou nenhum conhecimento sobre a estrutura subjacente. Além disso, a navegação visual de dados remove a necessidade de consultas SQL, e de toda complexidade que elas requerem. Acredita-se que esta abordagem possa trazer um paradigma inovador no que tange à compreensão de dados relacionais / Relational databases are rigid-structured data sources characterized by complex relationships among a set of relations (tables). Making sense of such relationships is a challenging problem because users must consider multiple relations, understand their ensemble of integrity constraints, interpret dozens of attributes, and draw complex SQL queries for each desired data exploration. In this scenario, we introduce a twofold methodology; we use a hierarchical graph representation to efficiently model the database relationships and, on top of it, we designed a visualization technique for rapidly relational exploration. Our results demonstrate that the exploration of databases is deeply simplified as the user is able to visually browse the data with little or no knowledge about its structure, dismissing the need of complex SQL queries. We believe our findings will bring a novel paradigm in what concerns relational data comprehension.

Em busca da documentação e otimização de seus processos, a área de Business Process Management (BPM) vem cada vez mais atraindo o interesse do meio empresarial, por ser um importante método no auxílio ao ganho de resultados, como redução de custos e aumento de produtividade. Modelar processos, entretanto, não basta. É preciso que se atente para métodos eficientes de armazená-los, permitindo que as informações sejam manipuladas e utilizadas de maneira prática e inteligente. A presente dissertação propõe duas abordagens para armazenamento de modelos de processo, uma em bancos de dados relacionais e outra em bancos de dados orientados a grafos, comparando-os através de aspectos como desempenho na execução das operações e proximidade da abordagem de cada um deles com os modelos de processos. Enquanto os bancos de dados relacionais são mais populares, sendo utilizados na maior parte das aplicações atuais, os bancos de dados orientados a grafos possuem propriedades e representação gráfica semelhantes aos modelos de processos. Foram realizados testes que visam analisar o desempenho de ambas as abordagens, além da facilidade dos usuários em interagir com os modelos propostos. Os resultados deste estudo podem ser utilizados para a criação de repositórios que compartilhem processos de maneira eficiente, bem como incentivar o estudo de novas maneiras para o armazenamento de processos. / Business Process Management (BPM) area has been increasingly attracted the interest of the business community because users are looking for documentation and optimization. These documents can be an important method in helping to gain results such as reduced costs and increased productivity. However, to model processes is not enough. It is necessary to pay attention to efficient storage methods, allowing information to be handled and used in a practical and intelligent way. The present article compares the use of relational databases and graph databases, considering aspects such as performance in the execution of operations and proximity of the approach of each of them with the process models. While relational databases are more popular, being used in most of the current applications, graph databases have properties and graphical representations similar to process models. The results of this study can be used to create repositories which can both share process efficiently, and encourage the study of new ways of storing processes.

Pitch Technologies specializes their work on the HLA standard, a standard that specifies data exchange between simulators. The company provides a solution for recording HLA data into a database as raw byte data entries. In this thesis, different design solutions to store and organize recorded HLA data in a manner that reflects the content of the data are proposed and implemented, with the aim of making the data possible to query and analyze after recording. The design solutions impact on storage, read- and write performance as well as usability are evaluated through a suite of tests run on a PostgreSQL database and a TimescaleDB database. It is concluded that none of the design alternatives is the best solution for all aspects, but the most promising combination is proposed.

No description available.

Protection of the visual environment begins with a comprehensive documentation and evaluation of existing conditions followed by the development of guidelines pertaining to future alterations. This thesis examines existing methods of visual assessment and the needs of the land planner for the purpose of understanding the necessary components of evaluating the visual environment effectively. The objective has been to develop a new method of visual documentation and evaluation that can be utilized by land planners for the visual assessment of road corridors. In order to achieve this objective, a visual assessment of a Significant road corridor in Blacksburg, Virginia has been conducted. Various necessary components have been included in the assessment and a relational database management program has been used in the storage of all collected data. As a result of this process, it was found that a new method, which borrows from past processes, addresses the needs of the land planner, and utilizes an interactive medium for storage of data, is successful in addressing the objective. The new method has been successful in including the necessary components such as qualitative evaluation with adaptive descriptive nomenclature and photographic documentation of the existing corridor. The database has many qualities which are meaningful to land planners. Relational database management programs have the capability of storing text as well as photographs. For land planners to view the various aspects of the corridor, a simple pressing of their computer mouse button moves the them from one aspect to another. / Master of Landscape Architecture

Medasolution is a virtual company designed by the author to handle Medicare insurance business. The web application (which uses ASP.net and SQL Server 2000) facilitates communication between Medasolution and all its clients: members, employers, brokers, and medicare providers through separate web pages based on their category levels. The program incorporates security so that it follows government privacy rules regarding client information.

Thesis (doctoral)--Universität zu Lübeck, 2006. / Includes bibliographical references (p. 161-169) and index.