On distributed data processing in data grid architecture for a virtual repository

The article describes the problem of integration of distributed, heterogeneous and fragmented collections of data with application of the virtual repository and the data grid concept. The technology involves: wrappers enveloping external resources, a virtual network (based on the peer-topeer technology) responsible for integration of data into one global schema and a distributed index for speeding-up data retrieval. Authors present a method for obtaining data from heterogeneously structured external databases and then a procedure of integration the data to one, commonly available, global schema. The core of the described solution is based on the Stack-Based Query Language (SBQL) and virtual updatable SBQL views. The system transport and indexing layer is based on the P2P architecture

State-of-the-art on evolution and reactivity

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in Rewerse. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks

CloudAnchor Smart Contracts

The CloudAnchor platform allows the negotiation of IaaS Cloud resources for Small and Medium Sized Enterprises (SME), either as resource providers or consumers. This project entails the research, design, and implementation of a solution based on smart contracts, with the goal of permanently recording and managing the contracts on a blockchain network. The usage of smart contracts enables safe contract code execution and raises the level of trust, integrity, and traceability of the platform contracts by keeping the data stored in a decentralised manner. To do so, a method to coordinate and submit transactions to the blockchain network must be implemented. The tests carried out indicate that the solution has been successfully implemented, with contract registration saved in a decentralised and safe manner. As a result, there was an increase in the platform’s execution time, caused by the new transactions made to the blockchain.A plataforma CloudAnchor permite a negociação e contratualização de recursos Cloud do tipo IaaS a pequenas e médias empresas, sejam elas fornecedoras ou clientes. Este trabalho inclui o estudo, projeto e implementação de uma solução baseada em smart contracts, com o objetivo de administrar e registar de forma permanente os contratos celebrados numa rede blockchain. A utilização de smart contracts permite executar o respetivo código de forma segura e aumentar o nível de confiança, integridade e rastreabilidade dos contratos celebrados na plataforma, guardando-os de forma descentralizada. Para tal, é necessário implementar um mecanismo de coordenação e submissão de transações para a rede blockchain. Os testes realizados permitiram concluir que a implementação da solução foi bem sucedida, passando os contratos a ficar guardados de forma descentralizada e segura. Em consequência, verificou-se um aumento do tempo de execução da plataforma provocado pelas novas transações com a blockchain

Survey of Models and Architectures to Ensure Linked Data Access

Mobile Access to the Web of Data is currently a real challenge in developing countries, mainly characterized by limited Internet connectivity and high penetration of mobile devices with the limited resources (such as cache and memory). In this paper, we survey and compare proposed solutions (such as models and architectures) that could contribute to solving this problem of mobile access to the Web of Data with intermittent Internet access. These solutions are discussed in relation to the underlying network architectures and data models considered. We present a conceptual study of peer-to-peer solutions based on gossip protocols dedicated to design the connected overlay networks. In addition, we provide a detailed analysis of client-server and data replication systems generally designed to ensure the local availability of data on the system. We conclude with some recommendations to achieve a connected architecture that provides mobile contributors with local access to the Web of data