Processing Regular Path Queries on Arbitrarily Distributed Data

Regular Path Queries (RPQs) are a type of graph query where answers are pairs of nodes connected by a sequence of edges matching a regular expression. We study the techniques to process such queries on a distributed graph of data. While many techniques assume the location of each data element (node or edge) is known, when the components of the distributed system are autonomous, the data will be arbitrarily distributed. As the different query processing strategies are equivalently costly in the worst case, we isolate query-dependent cost factors and present a method to choose between strategies, using new query cost estimation techniques. We evaluate our techniques using meaningful queries on biomedical data

Recovery Management of Long Running eBusiness Transactions

eBusiness collaboration and an eBusiness process are introduced as a context of a long running eBusiness transaction. The nature of the eBusiness collaboration sets requirements for the long running transactions. The ACID properties of the classical database transaction must be relaxed for the eBusiness transaction. Many techniques have been developed to take care of the execution of the long running business transactions such as the classical Saga and a business transaction model (BTM) of the business transaction framework. Those classic techniques cannot adequately take into account the recovery needs of the long running eBusiness transactions and they need to be further improved and developed. The expectations for a new service composition and recovery model are defined and described. The DeltaGrid service composition and recovery model (DGM) and the Constraint rules-based recovery mechanism (CM) are introduced as examples of the new model. The classic models and the new models are compared to each other and it is analysed how the models answer to the expectations. Neither new model uses the unaccustomed classification of atomicity even if the BTM includes the unaccustomed classifying of atomicity. A recovery model of the new models has improved the ability to take into account the data and control dependencies in the backward recovery. The new models present two different kinds of strategies to recover a failed service. The strategy of the CM increases the flexibility and the efficiency compared to the Saga or the BTF. The DGM defines characteristics that the CM does not have: a Delta-Enabled rollback, mechanisms for a pre-commit recoverability and for a post-commit recoverability and extends the concepts of a shallow compensation and a deep compensation. The use of them guarantees that an eBusiness process recovers always in a consistent state which is something the Saga, the BTM and the CM could not proof. The DGM offers also the algorithms of the important mechanisms. ACM Computing Classification System (CCS): C.2.4 [Distributed Systems]: Distributed application

Transferência inteligente de instruções digitais de montagem

Mestrado em Sistemas de InformaçãoThe German maritime industry has a strong economic influence, prevailing over competitors by offering a higher quality product and a higher degree of flexibility during design and building phases. In order to maintain its competitive edge, means to increase the productivity of a ship’s construction process are researched and developed. Under the PROSPER project, an Android application running augmented reality technology was developed to assist shipbuilders in the performance of their tasks. In this work, we researched organizational models capable of holding assembly instruction information later transfered to the application. Different wireless technologies and protocols were analyzed and studied to determine the most suitable transferring mechanisms. In the end, a Node.js server capable of handling complex assembly instructions requests was developed and tested using real-word scenarios. Throughout the development process, time was devoted to security measures in the protection of the server, end connections, and all information. Two different transferring methods were developed and testes, together with improvements to the overall transfer of assembly instructionsA indústria marítima alemã tem uma forte influência econômica, prevalecendo sobre os seus concorrentes, oferecendo um produto de maior qualidade e um maior grau de flexibilidade durante as fases de conceção e construção. A fim de manter a sua vantagem competitiva, fins para aumentar a produtividade do processo de construção de um navio são investigados e desenvolvidos. No âmbito do projecto PROSPER, uma aplicação Android foi desenvolvida para ajudar, através de realidade aumentada, construtores navais no desempenho das suas funções. Neste trabalho, investigamos modelos organizacionais capazes de armazenar informação pertinentes a instruções de montagem de navios, mais tarde transferidas para a aplicação. Diferentes tecnologias e protocolos sem fio foram analisados e estudados para determinar os mecanismos mais adequados para o procedimento de transferência. No final, um servidor Node.js capaz de lidar com complexas solicitações de instruções de montagem foi desenvolvido e testado utilizando cenários reais de montagem. Durante todo o processo de desenvolvimento, medidas de segurança na proteção do servidor, conexões entre servidor e clientes, e informações foram implementadas. Dois métodos distintos de transferência foram desenvolvidos e testados, juntamente com melhorias para a transferência global de instruções de montagem