An Overview of Event-based Facades for Modular Composition and Coordination of Multiple Applications

Complex software systems are usually developed as systems of systems (SoS’s) in which multiple constituent applications are composed and coordinated to fulfill desired system-level requirements. The constituent applications must be augmented with suitable coordination-specific interfaces, through which they can participate in coordinated interactions. Such interfaces as well as coordination rules have a crosscutting nature. Therefore, to increase the reusability of the applications and to increase the comprehensibility of SoS’s, suitable mechanisms are required to modularize the coordination rules and interfaces from the constituent applications. We introduce a new abstraction named as architectural event modules (AEMs), which facilitate defining constituent applications and desired coordination rules as modules of SoS’s. AEMs augment the constituent applications with event-based facades to let them participate in coordinated interactions. We introduce the EventArch language in which the concept of AEMs is implemented, and illustrate its suitability using a case study

Representing Variability in Software Architecture: A Systematic Literature Review

Variability in software - intensive systems is the ability of a software artefact (e.g., a system, subsystem, or component) to be extended, customised or configured for deployment in a specific context. Software Architecture is a high - level description of a software - intensive system that abstracts the system implementation details allowing the architect to view the system as a whole. Although variability in software architecture is recognised as a challenge in multiple domains, there has been no formal consensus on how variability should be captured or represented. The objective of this research was to provide a snapshot of the state - of - the - art on representing variability in software architecture while assessing the nature of the different approaches. To achieve this objective, a Systematic Literature Review (SLR) was conducted covering literature produced from January 1991 until June 2016. Then, grounded theory was used to conduct the analysis and draw conclusions from data, mini mising threats to validity. In this paper , we report on the findings from the study

Software Architecture Evolution

This chapter provides an overview, comparison and detailed treatment of the various state-of-the-art approaches to evolving software architectures. Furthermore, we discuss one particular framework for software architecture evolution in more detail

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

The ALI Architecture Description Language

Architecture Description Languages (ADLs) have emerged over the past two decades as a means to abstract details of large-scale systems in order to enable better intellectual control over the complete systems. Recently, there has been an explosion in the number of ADLs created in the research community. However, industrial adoption of these ADLs has been rather limited. This has been attributed to various reasons, including the lack of support of some ADLs for: variability management, requirements traceability, architectural artefact reusability and multiple architectural views. To overcome these limitations, this paper is a report on ALI, an ADL that was designed to complement existing work by adding mechanisms to address the aforementioned limitations. The ALI design principles, concepts, notations and formal semantics are presented in this paper. The notation is illustrated using two distinct case studies, one from the information systems domain " an Asset Management System (AMS); and another from the embedded systems domain - a Wheel Brake System (WBS)

Leveraging service-oriented business applications to a rigorous rule-centric dynamic behavioural architecture.

Today’s market competitiveness and globalisation are putting pressure on organisations to join their efforts, to focus more on cooperation and interaction and to add value to their businesses. That is, most information systems supporting these cross-organisations are characterised as service-oriented business applications, where all the emphasis is put on inter-service interactions rather than intra-service computations. Unfortunately for the development of such inter-organisational service-oriented business systems, current service technology proposes only ad-hoc, manual and static standard web-service languages such as WSDL, BPEL and WS-CDL [3, 7]. The main objective of the work reported in this thesis is thus to leverage the development of service-oriented business applications towards more reliability and dynamic adaptability, placing emphasis on the use of business rules to govern activities, while composing services. The best available software-engineering techniques for adaptability, mainly aspect-oriented mechanisms, are also to be integrated with advanced formal techniques. More specifically, the proposed approach consists of the following incremental steps. First, it models any business activity behaviour governing any service-oriented business process as Event-Condition-Action (ECA) rules. Then such informal rules are made more interaction-centric, using adapted architectural connectors. Third, still at the conceptual-level, with the aim of adapting such ECA-driven connectors, this approach borrows aspect-oriented ideas and mechanisms, and proposes to intercept events, select the properties required for interacting entities, explicitly and separately execute such ECA-driven behavioural interactions and finally dynamically weave the results into the entities involved. To ensure compliance and to preserve the implementation of this architectural conceptualisation, the work adopts the Maude language as an executable operational formalisation. For that purpose, Maude is first endowed with the notions of components and interfaces. Further, the concept of ECA-driven behavioural interactions are specified and implemented as aspects. Finally, capitalising on Maude reflection, the thesis demonstrates how to weave such interaction executions into associated services

Evolution of component and aspect-based product line architectures

Orientador: Cecília Mary Fischer RubiraTese (doutorado) ¿ Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Arquiteturas de linhas de produtos são essenciais para facilitar a evolução das linhas, pois ajudam a lidar com sua complexidade, abstraindo seus detalhes de implementação. A variabilidade arquitetural difere arquiteturas de linhas de produtos de arquiteturas de sistemas únicos. Ela reflete a existência de alternativas de projeto arquitetural e é expressa por meio de um conjunto de pontos de variação e variantes arquiteturais. A variabilidade arquitetural pode dificultar a evolução de arquiteturas de linhas produtos, pois a implementação da variabilidade software pode aumentar a complexidade da arquitetura com a possível adição de elementos e dependências extras. A variabilidade de linhas de produtos é usualmente capturada modelo de características e implementado pela arquitetura de linha de produtos. Entretanto, a implementação de características, pontos de variação e variantes podem estar espalhados por diversos elementos arquiteturais, o que dificulta a sua evolução. Em geral, cenários de evolução de linhas de produto envolvem adição e/ou remoção de características, mudança de uma característica obrigatória para opcional, entre outros. Quando cenários de evolução afetam características cujas implementações estão espalhadas na arquitetura, eles podem causar impacto de mudança em vários elementos arquiteturais. Estudos recentes exploram o uso de aspectos para modularizar a implementação de características em arquiteturas de linhas de produtos. Aspectos são usados para modularizar interesses transversais que, no contexto de linhas de produtos, são interesses que afetam diversas características. Contudo, esses estudos não consideram (i) arquiteturas componentizadas com interfaces explícitas e (ii) o uso integrado de componentes e aspectos para modularizar a implementação da variabilidade arquitetural. Idealmente aspectos devem ser modelados o mais cedo possível, de preferência, junto com o modelo de características para possibilitar a criação de arquiteturas bem estruturadas com aspectos. Todavia, não existem modelos que integrem o modelo de características e aspectos, nem métodos que consideram aspectos para gerar arquiteturas de linhas produtos a partir do modelo de características. A solução proposta nesta tese envolve inicialmente um estudo comparativo para mostrar a facilidade de evolução de arquiteturas de linhas de produtos propiciada pelo uso integrado de componentes e aspectos. Em seguida, é proposta uma visão estendida do modelo de características que permite representar características transversais. Essa visão, chamada de visão de características orientada a aspectos, é usada para criar arquiteturas de linhas de produtos orientadas a aspectos. Além disso, um modelo arquitetural de componentes é estendido para integrar aspectos para modularizar a variabilidade arquitetural. Por fim, o método FArM, que provê o mapeamento de modelo de características para modelos de arquitetura de linha de produtos, é estendido para considerar características transversais. Foram conduzidos dois estudos empíricos: um para avaliar se o uso integrado de componentes e aspectos facilita ou não a evolução de arquiteturas de linhas de produtos. O outro estudo empírico avalia a modelagem de características transversais e a extensão do método FArM propostos para projetar arquiteturas de linhas de produtos que sejam fáceis de evoluir. Os dois estudos apresentaram resultados promissores indicando que a solução proposta nesta tese facilita a evolução de arquiteturas de linhas de produtosAbstract: Product line architectures are essential to facilitate the evolution of product lines, as they handle their complexity by abstracting implementation details. Architectural variability is what differs product line architectures from single system architectures. It reflects the existence of alternative design options and it is expressed by a set of architectural variation points and variants. Architectural variability can hinder product line architecture evolution because the implementation of software variability can increase architecture complexity by possibly adding extra elements and dependencies. Product line variability is usually captured in the feature model and it is implemented by product line architectures. However, the implementation of features, variation points, and variants may be scattered over architectural elements, which can hinder its evolution. In general, product line evolution scenarios involve feature addition/removal, changing a mandatory feature to an optional feature, and so forth. When evolution scenarios affect features whose implementations are scattered over architecture, they can cause a great change impact on several architectural elements. Recent studies have explored the use of aspects to modularize feature implementation in product line architectures. Aspects can modularize crosscutting concerns, which, in the context of product lines, are concerns that affect several features. Nevertheless, these studies do not consider (i) componentized architectures with explicit interfaces, and (ii) the integration of aspects and components to modularize the implementation of architectural variability. Ideally, aspects should be modeled as soon as possible, preferably, together with the feature model in order to enable the design of well structured product line architectures with aspects. However, there are neither models which integrate features and aspects, nor methods that considers aspects to design product line architectures from the feature model. The solution proposed in this thesis involves a comparative study that presents the support for product line architecture evolution provided by the integration of components and aspects. Then, it is proposed an extended view of the feature model which enables to represent crosscutting features. This view, called aspect-oriented feature view, is used to design product line architectures with aspects. Lastly, the FArM method, which provides guidelines to map from the feature model to the product line architecture model, is extended to consider crosscutting features. Two empirical studies were conducted: one to assess whether the integration of components and aspects facilitates product line architecture evolution. The other empirical study evaluates whether the crosscutting feature modeling and the FArM method extension proposed supports the design of evolvable product line architectures. Both studies presented promising results which indicate that the solution proposed in this thesis facilitates product line architecture evolutionDoutoradoCiência da ComputaçãoDoutor em Ciência da Computaçã

Representing Variability in Software Architecture

Software Architecture is a high level description of a software intensive system that enables architects to have a better intellectual control over the complete system. It is also used as a communication vehicle among the various system stakeholders. Variability in software-intensive systems is the ability of a software artefact (e.g., a system, subsystem, or component) to be extended, customised, or configured for deployment in a specific context. Although variability in software architecture is recognised as a challenge in multiple domains, there has been no formal consensus on how variability should be captured or represented. In this research, we addressed the problem of representing variability in software architecture through a three phase approach. First, we examined existing literature using the Systematic Literature Review (SLR) methodology, which helped us identify the gaps and challenges within the current body of knowledge. Equipped with the findings from the SLR, a set of design principles have been formulated that are used to introduce variability management capabilities to an existing Architecture Description Language (ADL). The chosen ADL was developed within our research group (ALI) and to which we have had complete access. Finally, we evaluated the new version of the ADL produced using two distinct case studies: one from the Information Systems domain, an Asset Management System (AMS); and another from the embedded systems domain, a Wheel Brake System (WBS). This thesis presents the main findings from the three phases of the research work, including a comprehensive study of the state-of-the-art; the complete specification of an ADL that is focused on managing variability; and the lessons learnt from the evaluation work of two distinct real-life case studies