Towards a Taxonomy of Aspect-Oriented Programming.

As programs continue to increase in size, it has become increasingly difficult to separate concerns into well localized modules, which leads to code tangling- crosscutting code spread throughout several modules. Thus, Aspect-Oriented Programming (AOP) offers a solution to creating modules with little or no crosscutting concerns. AOP presents the notion of aspects, and demonstrates how crosscutting concerns can be taken out of modules and placed into a centralized location. In this paper, a taxonomy of aspect-oriented programming, as well as a basic overview and introduction of AOP, will be presented in order to assist future researchers in getting started on additional research on the topic. To form the taxonomy, over four-hundred research articles were organized into fifteen different primary categories coupled with sub-categories, which shows where some of the past research has been focused. In addition, trends of the research were evaluated and paths for future exploration are suggested

Resolving feature convolution in middleware systems

Middleware provides simplicity and uniformity for the development of distributed applications. However, the modularity of the architecture of middleware is starting to disintegrate and to become complicated due to the interaction of too many orthogonal concerns imposed from a wide range of application requirements. This is not due to bad design but rather due to the limitations of the conventional architectural decomposition methodologies. We introduce the principles of horizontal decomposition (HD) which addresses this problem with a mixed-paradigm middleware architecture. HD provides guidance for the use of conventional decomposition methods to implement the core functionalities of middleware and the use of aspect orientation to address its orthogonal properties. Our evaluation of the horizontal decomposition principles focuses on refactoring major middleware functionalities into aspects in order to modularize and isolate them from the core architecture. New versions of the middleware platform can be created through combining the core and the flexible selection of middleware aspects such as IDL data types, the oneway invocation style, the dynamic messaging style, and additional character encoding schemes. As a result, the primary functionality of the middleware is supported with a much simpler architecture and enhanced performance. Moreover, customization and configuration of the middleware for a wide-range of requirements becomes possible

A Domain-Specific IDL and its Compiler for Pervasive Computing Applications

Pervasive computing environments introduce new challenges for application development, due to the heterogeneity of the devices involved. In practice, pervasive computing applications rely on general-purpose middleware to manage this heterogeneity, but this approach does not provide programming support and verifications specific to the pervasive computing environment. In this paper, we present a domain-specific IDL and its compiler, dedicated to the development of pervasive computing applications. Our IDL is based on that of CORBA and provides declarative support for concisely characterizing a pervasive computing environment. This description is (1) to be used by programmers as a high-level reference to develop applications that coordinate entities of the target environment and (2) to be passed to a compiler that generates a framework dedicated to the target environment. This process enables verifications to be performed prior to runtime on both the declared environment and a given application. Furthermore, customized operations are automatically generated to support the development of pervasive computing activities, such as service discovery and session negotiation for stream-oriented devices. We have implemented a framework generator and have used it to generate frameworks targeting pervasive computing areas such as building surveillance, advanced telecommunications and home automation

Exception handling in the development of fault-tolerant component-based systems

Orientador: Cecilia Mary Fischer RubiraTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Mecanismos de tratamento de exceções foram concebidos com o intuito de facilitar o gerenciamento da complexidade de sistemas de software tolerantes a falhas. Eles promovem uma separação textual explícita entre o código normal e o código que lida com situações anormais, afim de dar suporte a construção de programas que são mais concisos fáceis de evoluir e confáveis. Diversas linguagens de programação modernas e a maioria dos modelos de componentes implementam mecanismos de tratamento de exceções. Apesar de seus muitos benefícios, tratamento de exceções pode ser a fonte de diversas falhas de projeto se usado de maneira indisciplinada. Estudos recentes mostram que desenvolvedores de sistemas de grande escala baseados em infra-estruturas de componentes têm hábitos, no tocante ao uso de tratamento de exceções, que tornam suas aplicações vulneráveis a falhas e difíceis de se manter. Componentes de software criam novos desafios com os quais mecanismos de tratamento de exceções tradicionais não lidam, o que aumenta a probabilidade de que problemas ocorram. Alguns exemplos são indisponibilidade de código fonte e incompatibilidades arquiteturais. Neste trabalho propomos duas técnicas complementares centradas em tratamento de exceções para a construção de sistemas tolerantes a falhas baseados em componentes. Ambas têm ênfase na estrutura do sistema como um meio para se reduzir o impacto de mecanismos de tolerância a falhas em sua complexidade total e o número de falhas de projeto decorrentes dessa complexidade. A primeira é uma abordagem para o projeto arquitetural dos mecanismos de recuperação de erros de um sistema. Ela trata do problema de verificar se uma arquitetura de software satisfaz certas propriedades relativas ao fluxo de exceções entre componentes arquiteturais, por exemplo, se todas as exceções lançadas no nível arquitetural são tratadas. A abordagem proposta lança de diversas ferramentas existentes para automatizar ao máximo esse processo. A segunda consiste em aplicar programação orientada a aspectos (AOP) afim de melhorar a modularização de código de tratamento de exceções. Conduzimos um estudo aprofundado com o objetivo de melhorar o entendimento geral sobre o efeitos de AOP no código de tratamento de exceções e identificar as situações onde seu uso é vantajoso e onde não éAbstract: Exception handling mechanisms were conceived as a means to help managing the complexity of fault-tolerant software. They promote an explicit textual separation between normal code and the code that deals with abnormal situations, in order to support the construction of programs that are more concise, evolvable, and reliable. Several mainstream programming languages and most of the existing component models implement exception handling mechanisms. In spite of its many bene?ts, exception handling can be a source of many design faults if used in an ad hoc fashion. Recent studies show that developers of large-scale software systems based on component infrastructures have habits concerning the use of exception handling that make applications vulnerable to faults and hard to maintain. Software components introduce new challenges which are not addressed by traditional exception handling mechanisms and increase the chances of problems occurring. Examples include unavailability of source code and architectural mismatches. In this work, we propose two complementary techniques centered on exception handling for the construction of fault-tolerant component-based systems. Both of them emphasize system structure as a means to reduce the impactof fault tolerance mechanisms on the overall complexity of a software system and the number of design faults that stem from complexity. The ?rst one is an approach for the architectural design of a system?s error handling capabilities. It addresses the problem of verifying whether a software architecture satis?es certain properties of interest pertaining the ?ow of exceptions between architectural components, e.g., if all the exceptions signaled at the architectural level are eventually handled. The proposed approach is based on a set of existing tools that automate this process as much as possible. The second one consists in applying aspect-oriented programming (AOP) to better modularize exception handling code. We have conducted a through study aimed at improving our understanding of the efects of AOP on exception handling code and identifying the situations where its use is advantageous and the ones where it is notDoutoradoDoutor em Ciência da Computaçã

Software Architecture Evolution through Dynamic AOP

Modern computing and network environments demand a high degree of adaptability from applications. At run time, an application may have to face many changes: in conguration, in protocols used, in terms of the available resources, etc. Many such changes can only be adequately addressed through dynamic evolution of the software architecture of the application. In this paper, we propose a novel approach to dynamically evolve a software architecture based on run-time aspect oriented programming. In our framework, a system designer/administrator can control the architecture of an application by dynamically inserting and removing code extensions. It is even possible to replace a signicant part of the underlying middleware infrastructure without stopping the application. The novelty of this work is that it allows for a much more flexible development strategy as it delegates issues like middleware choice and adherence to an architectural specication to a framework enhanced by dynamic code extensions

Barriers and adoption of energy efficiency measures in buildings of micro, small and medium-sized Portuguese companies

Indispensable nowadays and for future generations, electricity must be used efficiently since it is a scarce resource and have serious repercussions in the environment due to the process of how it is generated. Energy efficiency is vital to reduce energy bills, improve energy security and also as a tool to combat climate change reducing the pressure in the environment. Being the percentage of MSMEs in Portugal 99,9% of the total of enterprises and representing a significant share of the country’s energy consumption justifies the need to carry out this study. Due to the absence of secondary data, an online survey was carried out. Based on theories of agency and absorption capacity it is studied the adoption and barriers to adoption of four crosscutting, ancillary energy efficiency measures (lighting, insulation, heating replacement and heating operations. Evidence is found that absorptive capacity factors are a key factor for adopting more efficient and profitable measures. It may be necessary to create policies to support MSMEs that aim to inform and assist them thus filling the lack of energy managers and energy management systems since these imply costs that smaller companies cannot afford. Although the subsidiaries suffer pressures explained with agency theory, they can also benefit from learning moments. Most of the decisions and barriers considered by MSMEs are not supported either by audits or by energy management professionals since more than 65% of the respondents have never performed an energy audit and more than 82% do not have an energy manager. It is necessary to create more aggressive awareness-raising policies in order to show clearly the individual benefit that each EEM provides to each MSMEs.Indispensável hoje em dia e para as gerações futuras, a eletricidade deve ser utilizada de forma eficiente, uma vez que é um recurso escasso e tem sérias repercussões no meio ambiente devido ao seu processo de geração. A eficiência energética é vital para reduzir as despesas de energia, melhorar a segurança energética e também como uma ferramenta para combater as alterações climáticas, reduzindo a pressão no meio ambiente. Sendo a percentagem de PMEs, em Portugal, 99,9% do total de empresas e representando uma parcela significativa do consumo de energia do país justifica a necessidade da realização deste estudo. Devido à ausência de dados secundários, foi realizada uma Recolha de dados primária. Com base nas teorias da agência e da capacidade de absorção, estuda-se a adoção e barreiras à adoção de quatro medidas transversais de eficiência energética auxiliares (iluminação, isolamento, substituição do sistema aquecimento e operações do sistema de aquecimento). Verifica-se que a capacidade de absorção é um fator chave para a adoção de tecnologias mais eficientes. Pode ser necessário criar políticas de apoio às PMEs que visem informá-las e auxiliá-las, colmatando, assim, a falta de gestores de energia e de sistemas de gestão de energia, pois estes implicam custos que as empresas mais pequenas não conseguem suportar. Além disso, a maioria das decisões e barreiras consideradas pelas PMEs não é apoiada por auditorias ou por profissionais de gestão de energia, já que mais de 65% dos entrevistados nunca realizaram uma auditoria energética e mais de 82% não tem um gestor de energia. Poderá ser necessário criar políticas de consciencialização mais agressivas de modo a mostrar claramente o benefício individual que cada MEE proporciona a cada uma das PMEs

Petri net model decomposition - a model based approach supporting distributed execution

Dissertação apresentada para obtenção do Grau de Doutor em Engenharia Electrotécnica, Especialidade de Sistemas Digitais, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaModel-based systems development has contributed to reducing the enormous difference between the continuous increase of systems complexity and the improvement of methods and methodologies available to support systems development. The choice of the modeling formalism is an important factor for success-fully increasing productivity. Petri nets proved to be a suitable candidate for being chosen as a system specification language due to their natural support of modeling processes with concurrency, synchronization and resource sharing, as well as the mechanisms of composition and decomposition. Also having a formal representation reinforces the choice, given that the use of verification tools is fundamental for complex systems development. This work proposes a method for partitioning Petri net models into concurrent sub-models, supporting their distributed implementation. The IOPT class (Input-Output Place Transition) is used as a reference class. It is extended by directed synchronous communication channels, enabling the com- munication between the generated sub-models. Three rules are proposed to perform the partition, and restrictions of the proposed partition method are identified. It is possible to directly compose models which result from the partitioning operation, through an operation of model addition. This allows the re-use of previously obtained models, as well as the easy modification of the intended system functionalities. The algorithms associated with the implementation of the partition operation are presented, as well as its rules and other procedures. The proposed methods are validated through several case studies emphasizing control components of automation systems