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Persistent and secure store for web objects is an attractive feature in today?s web world and possess a good potential for exploration. Persistence of a storage mechanism refers to its ability to store an object for extremely long time periods. Resilience refers to its fault tolerance ability or its ability to retrieve the object completely even if a part of that object is lost due to any catastrophic failures like disk failure. It is also important that this storage mechanism is able to store this object in a secure manner. In the current world, usability of any storage mechanism is enhanced multiple times if it could be used from a web interface. This thesis considers different techniques that provide these properties and proposes a storage mechanism that makes use of information dispersal techniques that is suited to store data securely, with an emphasis on availability and resilience. A working prototype of this storage mechanism was developed as a part of this thesis and is made available as a library for program developers. This library provides APIs to store and retrieve data as well as a daemon for error control. The APIs to store and retrieve data also accepts HTTP requests, which increase its usability to web developers. The performance of this prototype was measured and is presented using graphs. Finally a demonstration of the applications of this prototype is also provided.

Database systems research is an old and well-established field in computer science. Many of the key concepts appeared as early as the 60s, while the core of relational databases, which have dominated the database world for a while now, was solidified during the 80s. However, the underlying hardware has not displayed such stability in the same period, which means that a lot of assumptions that were made about the hardware by early database systems are not necessarily true for modern computer architectures. In particular, over the last few decades there have been two notable consistent trends in the evolution of computer hardware. The first is that the memory hierarchy of mainstream computer systems has been getting deeper, with its different levels moving away from each other, and new levels being added in between as a result, in particular cache memories. The second is that, when it comes to data transfers between any two adjacent levels of the memory hierarchy, access latencies have not been keeping up with transfer rates. The challenge is therefore to adapt database index structures so that they become immune to these two trends. The latter is addressed by gradually increasing the size of the data transfer unit; the former, by organizing the data so that it exhibits good locality for memory transfers across multiple memory boundaries. We have developed novel structures that facilitate both of these strategies. We started our investigation with the venerable B+-tree, which is the cornerstone order-preserving index of any database system, and we have developed a novel pointer-free tree structure for its pages that optimizes its cache performance and makes it immune to the page size. We then adapted our approach to the R-tree and the GiST, making it applicable to multi-dimensional data indexes as well as generalized indexes for any abstract data type. Finally, we have investigated our structure in the context of main memory alone, and have demonstrated its superiority over the established approaches in that setting too. While our research has its roots in data structures and algorithms theory, we have conducted it with a strong experimental focus, as the complex interactions within the memory hierarchy of a modern computer system can be quite challenging to model and theorize about effectively. Our findings are therefore backed by solid experimental results that verify our hypotheses and prove the superiority of our structures over competing approaches.

Cloudspeicherdienste sind zu einem Standard für den Austausch großer Datenmengen in virtuellen Gemeinschaften geworden, sowohl im privaten Umfeld als auch im öffentlichen Bereich. Einfache Bedienbarkeit sowie nahtlose Integration in Applikationen, Betriebssystemen und Endgeräten sind wesentliche Bausteine dieses Siegeszuges.

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2017-03-31T11:47:37Z No. of bitstreams: 1 Marcelino Sato Matsuda.pdf: 1145713 bytes, checksum: 12b85b74f6ee1218d67654c791556f69 (MD5) / Made available in DSpace on 2017-03-31T11:47:37Z (GMT). No. of bitstreams: 1 Marcelino Sato Matsuda.pdf: 1145713 bytes, checksum: 12b85b74f6ee1218d67654c791556f69 (MD5) Previous issue date: 2017-03-20 / The facility of new equipments associated with the different ways people communicate has changed social behavior and the way of practicing the legal business. In 2014, the Civil Mark of Internet took effect, without taking care of the storage of legal business data nor the information content to be stored. Which leads us to ask: How to guarantee the effectiveness of consumer rights at the necessary moment to prove the legal business performed through information technologies? In order to solve this question, we start from general assumptions applied to consumer rights, the relevant legislation to the Internet, the law projects related to e-commerce and the prescription of the Civil Code to show the necessity of storing the legal business information in log files by 10 years. The present study has importance for the effectiveness of consumer protection projected over time and in the rescue of information. Furthermore, we believe that this study may contribute with other studies on the same matter, since information technology is a matter quite discussed nowadays / A facilidade dos novos equipamentos associados aos vários modos das pessoas se comunicarem alterou o comportamento social e a maneira de praticar os negócios jurídicos. Em 2014, o Marco Civil da Internet entrou em vigor, sem cuidar do armazenamento dos dados dos negócios jurídicos, nem do conteúdo da informação a ser armazenada. O que nos levou a perguntar: Como garantir a efetividade dos direitos do consumidor no momento de provar os negócios jurídicos realizados por meio das tecnologias da informação? Para solução desta indagação, partimos de premissas gerais aplicadas ao direito do consumidor, à legislação correspondente à internet, aos projetos de lei correspondentes ao comércio eletrônico e à prescrição do Código Civil para mostrar a necessidade do armazenamento das informações dos negócios jurídicos em arquivos log pelo período de 10 anos. O presente estudo tem importância para efetividade da tutela do consumidor projetada no tempo e no resgate da informação. Além disso, acreditamos que esta proposta pode contribuir com outros estudos que tratam do tema, visto que a tecnologia da informação é assunto bastante discutido atualmente

Managing data is one of the main challenges in distributed systems and computer science in general. Data is created, shared, and managed across heterogeneous distributed systems of users, services, applications, and devices without a clear and comprehensive data model. This technological fragmentation and lack of a common data model result in a poor understanding of what data is, how it evolves over time, how it should be managed in a distributed system, and how it should be protected and shared. From a user perspective, for example, backing up data over multiple devices is a hard and error-prone process, or synchronising data with a cloud storage service can result in conflicts and unpredictable behaviours. This thesis identifies three challenges in data management: (1) how to extend the current data abstractions so that content, for example, is accessible irrespective of its location, versionable, and easy to distribute; (2) how to enable transparent data storage relative to locations, users, applications, and services; and (3) how to allow data owners to protect data against malicious users and automatically control content over a distributed system. These challenges are studied in detail in relation to the current state of the art and addressed throughout the rest of the thesis. The artefact of this work is the Sea of Stuff (SOS), a generic data model of immutable self-describing location-independent entities that allow the construction of a distributed system where data is accessible and organised irrespective of its location, easy to protect, and can be automatically managed according to a set of user-defined rules. The evaluation of this thesis demonstrates the viability of the SOS model for managing data in a distributed system and using user-defined rules to automatically manage data across multiple nodes.