NoSQL databases were initially devised to support a few concrete extreme scale applications. Since the specificity and scale of the target systems justified the investment of manually crafting application code their limited query and indexing capabilities were not a major im- pediment. However, with a considerable number of mature alternatives now available there is an increasing willingness to use NoSQL databases in a wider and more diverse spectrum of applications and, to most of them, hand-crafted query code is not an enticing trade-off. In this paper we address this shortcoming of current NoSQL databases with an effective approach for executing SQL queries while preserving their scalability and schema flexibility. We show how a full-fledged SQL engine can be integrated atop of HBase leading to an ANSI SQL compli- ant database. Under a standard TPC-C workload our prototype scales linearly with the number of nodes in the system and outperforms a NoSQL TPC-C implementation optimized for HBase.

All companies developing their business on the Web, not only giants like Google or Facebook but also small com- panies focused on niche markets, face scalability issues in data management. The case study of this paper is the content management systems for classified or commercial advertise-ments on the Web. The data involved has a very significant growth rate and a read-intensive access pattern with a reduced update rate. Typically, data is stored in traditional file systems hosted on dedicated servers or Storage Area Network devices due to the generalization and ease of use of file systems. However, this ease in implementation and usage has a disadvantage: the centralized nature of these systems leads to availability, elasticity and scalability problems. The scenario under study, undemanding in terms of the system's consistency and with a simple interaction model, is suitable to a distributed database, such as Cassandra, conceived precisely to dynamically handle large volumes of data. In this paper, we analyze the suitability of Cassandra as a substitute for file systems in content management systems. The evaluation, conducted using real data from a produc- tion system, shows that using Cassandra, one can easily get horizontal scalability of storage, redundancy across multiple independent nodes, and load distribution imposed by the periodic activities of safeguarding data, while ensuring a comparable performance to that of a file system.

Label Ranking (LR) problems, such as predicting rankings of nancial analysts, are becoming increasingly important in data mining. While there has been a signicant amount of work on the development of learning algorithms for LR in recent years, preprocessing methods for LR are still very scarce. However, some methods, like Naive Bayes for LR and APRIORI-LR, cannot deal with real-valued data directly. As a make-shift solution, one could consider conventional discretization methods used in classication, by simply treating each unique ranking as a separate class. In this paper, we show that such an approach has several disadvantages. As an alternative, we propose an adaptation of an existing method, MDLP, specically for LR problems. We illustrate the advantages of the new method using synthetic data. Additionally, we present results obtained on several benchmark datasets. The results clearly indicate that the discretization is performing as expected and in most cases improves the results of the learning algorithms.

The major challenge in fault-tolerant replicated transactional databases is providing efficient distributed concurrency control that allows non-conflicting transactions to execute concurrently. A common approach is to partition the data according to the data access patterns of the workload, assuming that this will allow operations in each partition to be scheduled independently and run in parallel.
The effectiveness of this approach hinges on the characteristics of the workload: (i) the ability to identify such partitions and (ii) the actual number of such partitions that arises. Performance results that have been presented to support such proposals are thus tightly linked to the simplistic synthetic benchmarks that have been used. This is worrisome, since these benchmarks have not been conceived for this purpose and the resulting definition of partitions might not be representative of real applications. In this paper we contrast a more complex synthetic benchmark (TPC-E) with a real application in the same area (financial brokerage), concluding that the real setting makes it much harder to determine a correct partition of the data and that sub-optimal partitioning severely constrains the performance of replication.

A plataforma APEX foi desenvolvida para a prototipagem de ambientes de computação ubíqua. Neste artigo exploramos a sua aplicabilidade ao desenvolvimento de jogos sérios, ou seja, jogos que para além de uma componente lúdica, possuem uma componente instrutiva e formativa. Em concreto, descrevemos o Jogo da Asma. Um jogo que pretende chamar a atenção das crianças para os factores causadores de ataques de asma, bem como transmitir conhecimento sobre como os evitar. Para além de descrever o jogo, descrevem-se os resultados de um estudo em que se procurou avaliar quer a viabilidade da utilização da plataforma na criação de jogos sérios, quer a usabilidade do próprio jogo.

Cada vez mais as interfaces gráficas são um ponto-chave entre a comunicação dos utilizadores e o sistema. Para garantir que estas executam devidamente uma adequada fases de testes é essencial. No entanto, a execução de testes numa interface é um processo dispendioso e moroso, sendo estes tipicamente executados de forma manual. Neste artigo é explorada a automatização do processo de teste de interfaces para aplicações Web. Adopta-se uma abordagem de testes baseados em modelos. Os casos de teste são gerados recorrendo a modelos de tarefas e o comportamento da interface comparado com o que está prescrito no modelos de tarefas. Uma ferramenta que suporta a abordagem está em desenvolvimento.

Software has become so complex that it is increasingly hard to have a complete understanding of how a particular system will behave. Web applications, their user interfaces in particular, are built with a wide variety of technologies making them particularly hard to debug and maintain. Reverse engineering techniques, either through static analysis of the code or dynamic analysis of the running application, can be used to help gain this understanding. Each type of technique has its limitations. With static analysis it is difficult to have good coverage of highly dynamic applications, while dynamic analysis faces problems with guaranteeing that generated models fully capture the behavior of the system. This paper proposes a new hybrid approach for the reverse engineering of web applications' user interfaces. The approach combines dynamic analyzes of the application at runtime, with static analyzes of the source code of the event handlers found during interaction. Information derived from the source code is both directly added to the generated models, and used to guide the dynamic analysis.