Improving Reuse of Distributed Transaction Software with Transaction-Aware Aspects

Implementing crosscutting concerns for transactions is difficult, even using Aspect-Oriented Programming Languages (AOPLs) such as AspectJ. Many of these challenges arise because the context of a transaction-related crosscutting concern consists of loosely-coupled abstractions like dynamically-generated identifiers, timestamps, and tentative value sets of distributed resources. Current AOPLs do not provide joinpoints and pointcuts for weaving advice into high-level abstractions or contexts, like transaction contexts. Other challenges stem from the essential complexity in the nature of the data, operations on the data, or the volume of data, and accidental complexity comes from the way that the problem is being solved, even using common transaction frameworks. This dissertation describes an extension to AspectJ, called TransJ, with which developers can implement transaction-related crosscutting concerns in cohesive and loosely-coupled aspects. It also presents a preliminary experiment that provides evidence of improvement in reusability without sacrificing the performance of applications requiring essential transactions. This empirical study is conducted using the extended-quality model for transactional application to define measurements on the transaction software systems. This quality model defines three goals: the first relates to code quality (in terms of its reusability); the second to software performance; and the third concerns software development efficiency. Results from this study show that TransJ can improve the reusability while maintaining performance of TransJ applications requiring transaction for all eight areas addressed by the hypotheses: better encapsulation and separation of concern; loose Coupling, higher-cohesion and less tangling; improving obliviousness; preserving the software efficiency; improving extensibility; and hasten the development process

Improving Reuse and Maintainability of Communication Software With Conversation-Aware Aspects

Inter-process communications (IPC) are ubiquitous in today’s software systems, yet they are rarely treated as first-class programming concepts. Implementing crosscutting concerns for message-based IPC are difficult, even using aspect-oriented programming languages (AOPL) such as AspectJ. Many of these challenges are because the context of a communication-related crosscutting concern is often a conversation consisting of message sends and receives. Hence, developers typically have to implement communication protocols manually using primitive operations, such as connect, send, receive, and close. This dissertation describes an extension to AspectJ, called CommJ, with which developers can implement communication-related concerns in cohesive and loosely coupled aspects. It then presents preliminary, but encouraging results from a subsequent study that begin by defining a reuse and maintenance quality model. Subsequently the results show seven different ways in which CommJ can improve the reusability and maintainability of applications requiring network communications

Dagstuhl News January - December 2006

"Dagstuhl News" is a publication edited especially for the members of the Foundation "Informatikzentrum Schloss Dagstuhl" to thank them for their support. The News give a summary of the scientific work being done in Dagstuhl. Each Dagstuhl Seminar is presented by a small abstract describing the contents and scientific highlights of the seminar as well as the perspectives or challenges of the research topic

Uma abordagem de otimização multiobjetivo para projeto arquitetural de linha de produto de software

Resumo: A indústria de software tem adotado a abordagem de Linha de Produto de Software (LPS) com o objetivo de aumentar o reúso de software e diminuir o tempo de produção e os custos de desenvolvimento dos produtos. Nessa abordagem, o principal artefato e a arquitetura de LPS (PLA - Product Line Architecture). No entanto, obter uma PLA modular, extensível e reusável e uma tarefa não trivial. O arquiteto pode se apoiar em métricas arquiteturais para definir e melhorar o projeto da PLA. Contudo, essa tarefa pode envolver vários fatores, muitas vezes conflitantes entre si, e encontrar o melhor trade-off entre as métricas utilizadas para avaliar o projeto transforma o projeto de PLA em uma tarefa que demanda grande esforço humano. Nesse contexto, o projeto de PLA pode ser formulado como um problema de otimização com varios fatores. Porém, elaborar um projeto que atenda a todos os fatores envolvidos pode ser mais difícil do que reconhecer um bom projeto. Problemas da Engenharia de Software similares a esse tem sido eficientemente resolvidos com algoritmos de busca em um campo de pesquisa conhecido como Engenharia de Software Baseada em Busca (SBSE - Search Based Software Engineering). Entretanto, as abordagens existentes utilizadas para otimizar arquiteturas de software nãao são apropriadas para projeto de PLAs, pois não consideram características específicas de LPS. Desse modo, este trabalho propõe uma abordagem de otimização multiobjetivo automatizada para avaliar e melhorar um projeto de PLA no que tange a modularização de características, estabilidade do projeto e extensibilidade de LPS. A abordagem proposta inclui: (a) um processo sistemático para conduzir a otimização de projeto de PLA por meio de algoritmos de busca; (b) um metamodelo que permite que esses algoritmos manipulem projetos de PLA; (c) novos operadores de busca para evoluir projetos de PLA em termos de modularização de características; e (d) um tratamento multiobjetivo para o problema de projeto de PLA. Esse tratamento multiobjetivo engloba métricas que indicam a modularização de características e a extensibilidade de LPS, além de métricas convencionais para medir princípios básicos de projeto como coesão e acoplamento. Ao final do processo de otimização, um conjunto de possíveis soluções de projeto de PLA que representam os melhores trade-off entre os objetivos otimizados e retornado. O arquiteto deve selecionar uma solução de acordo com as suas prioridades. A ferramenta OPLA-Tool foi desenvolvida para instanciar a abordagem usando algoritmos evolutivos multiobjetivos, os quais tem sido usados com sucesso na área de SBSE. Utilizando a OPLA-Tool, quatro estudos empíricos foram realizados com nove PLAs para avaliar: os operadores de busca propostos; o uso das métricas de LPS; e os algoritmos escolhidos. Em comparação às PLAs originais, os resultados mostraram que a abordagem proposta consegue gerar projetos mais estáveis, mais elegantes e com melhor modularização de características

Phenomena at the border between quantum physics and general relativity

In this thesis we shall present a collection of research results about phenomena that lie at the interface between quantum physics and general relativity. The motivation behind our research work is to find alternative ways to tackle the problem of a quantum theory of/for gravitation. In the general introduction, we shall briefly recall some of the characteristics of the well-established approaches to this problem that have been developed since the beginning of the middle of the last century. Afterward we shall illustrate why one would like to engage in alternative paths to better understand the problem of a quantum theory of/for gravitation, and the extent to which they will be able to shed some light into this problem. In the first part of the thesis, we shall focus on formulating physics without Lorentz invariance. In the introduction to this part we shall describe the motivations that are behind such a possible choice, such as the possibility that the physics at energies near Planck regime may violate Lorentz symmetry. In the following part we shall first consider a minimalist way of breaking Lorentz invariance by renouncing the relativity principle, that corresponds to the introduction of a preferred frame, the aether frame. In this case we shall look at the transformations between a generic inertial frame and the aether frame still requiring the transformations to be linear. The second step is to establish the transformations for the energy and momentum in order to define some dynamics and design possible experiments to test such assumptions. As an application we shall present two compelling models that minimally break Lorentz invariance, the first one only in the energy-momentum sector, the second one in the transformation between inertial frames. Following along the line of physics without Lorentz invariance, we shall next explore some threshold theorems in both scattering and decay processes by considering only the existence of some energy momentum relation E(p), without making any further assumption. We shall see that quite a lot can be said and that 3-momenta can behave in a complicated and counter-intuitive manner. In the second part of the thesis we shall address the thermodynamics of space-time and the important role played by entropy. In the introduction we shall outline the idea of induced gravity, which is the motivation behind this possible interpretation of general relativity as a mean field theory of some underlying microscopic degrees of freedom. In the next chapter we shall partially review Jacobson's thermodynamic derivation of the Einstein equations and generalise it to a generic birfucate null surface. The interesting result we shall see is that, given the construction of the thermodynamic system via some virtual constantly accelerating observers, we can assign a "virtual" definition of Clausius entropy to essentially arbitrary causal horizons. To conclude this part we shall present some of the mathematical properties of entropy. In particular we shall focus on the simpler case of single-channel Shannon entropy and study under which conditions it is infinite, even though the probability distribution is normalisable. In the last part, we shall describe a proposal for a space-base experiment to test the effects of acceleration and gravity of quantum physics. In principle, the results of such an experiment could shed some light on fundamental questions about the overlap of quantum theory and general relativity; at the same time, they may enable experimentalists interested to implement quantum communication into space based technology, to correct adverse gravitational effects. We conclude with a brief discussion of lessons learned from these different approaches