Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

An overview of AspectJ

Today's society increasingly depends on software systems deployed in large companies, banks, airports, and so on. These systems must be available 24/7 and continuously adapt to varying environmental conditions and requirements. Such dynamically adaptive systems exhibit degrees of variability that depend on user needs and runtime fluctuations in their contexts. The paper presents an approach for specifying and executing dynamically adaptive software systems that combines model-driven and aspect-oriented techniques to help engineers tame the complexity of such systems while offering a high degree of automation and validation.

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Models@ Run.time to Support Dynamic Adaptation

A survey on engineering approaches for self-adaptive systems

The complexity of information systems is increasing in recent years, leading to increased effort for maintenance and configuration. Self-adaptive systems (SASs) address this issue. Due to new computing trends, such as pervasive computing, miniaturization of IT leads to mobile devices with the emerging need for context adaptation. Therefore, it is beneficial that devices are able to adapt context. Hence, we propose to extend the definition of SASs and include
context adaptation. This paper presents a taxonomy of self-adaptation and a survey on engineering SASs. Based on the taxonomy and the survey, we motivate a new perspective on SAS including context adaptation.

A survey on engineering approaches for self-adaptive systems (extended version)

Since software systems need to be continuously available under varying conditions, their ability to evolve at runtime is increasingly seen as one key issue. Modern programming frameworks already provide support for dynamic adaptations. However the high-variability of features in Dynamic Adaptive Systems (DAS) introduces an explosion of possible runtime system configurations (often called modes) and mode transitions. Designing these configurations and their transitions is tedious and error-prone, making the system feature evolution difficult. While Aspect-Oriented Modeling (AOM) was introduced to improve the modularity of software, this paper presents how an AOM approach can be used to tame the combinatorial explosion of DAS modes. Using AOM techniques, we derive a wide range of modes by weaving aspects into an explicit model reflecting the runtime system. We use these generated modes to automatically adapt the system. We validate our approach on an adaptive middleware for home-automation currently deployed in Rennes metropolis.

https://www.irisa.fr/triskell/publis/2009/Morin09a.pdf

Taming Dynamically Adaptive Systems using models and aspects

We present WildCAT, an extensible Java framework to ease the creation of context-aware applications. WildCAT provides a simple yet powerful dynamic model to represent an application's execution context. The context information can be accessed by application programmers through two complimentary interfaces: synchronous requests (pull mode) and asynchronous notifications (push mode). Internally, WildCAT is designed as a framework supporting different levels of extensions, from the simple configuration of the default generic implementation to completely new implementations tailored to specific needs. A given application can mix different implementations for different aspects of its context while only depending on WildCAT's simple and unified API.

WildCAT: a generic framework for context-aware applications

Nowadays, application developers have to deal with increasingly variable execution contexts, requiring the creation of applications able to adapt themselves autonomously to the evolutions of this context. In this paper, we show how an aspect-oriented approach enables the development of self-adaptive applications where the adaptation code is well modularized, both spatially and temporally. Concretely, we propose SAFRAN, an extension of the Fractal component model for the development of the adaptation aspect as reactive adaptation policies. These policies detect the evolutions of the execution context and adapt the base program by reconfiguring it. This way, SAFRAN allows the modular development of adaptation policies and their dynamic weaving into running applications.

An aspect-oriented approach for developing self-adaptive fractal components

Component-based systems must support dynamic reconfigurations to adapt to their execution context, but not at the cost of reliability. Fractal provides intrinsic support for dynamic reconfiguration, but its definition in terms of low-level APIs makes it complex to write reconfigurations and to ensure their reliability. This article presents a language-based approach to solve these issues: direct and focused language support for architecture navigation and reconfiguration make it easier both to write the reconfigurations and to ensure their reliability. Concretely, this article presents two languages: (1) FPath, a domain-specific language that provides a concise yet powerful notation to navigate inside and query Fractal architectures, and (2) FScript, a scripting language that embeds FPath and supports the definition of complex reconfigurations. FScript ensures the reliability of these reconfigurations thanks to sophisticated run-time control, which provides transactional semantics (ACID properties) to the reconfigurations.

FPath and FScript: Language support for navigation and reliable reconfiguration of Fractal architectures

In this paper we present FScript, a Domain-Speci c Language used to program structural recon gurations of Fractal architectures. Compared to the use of the standard Fractal APIs in a general purpose language, FScript o ers better syntactic support for navigation, more dynamicity, and guarantees on the recon gurations (termination, atomicity, consistency, and isolation). FScript introduces a new notation, called FPath, which is designed to express queries on Fractal architectures, navigating inside them and selecting elements according to predicates. It also provides access to all the primitive recon guration actions available in Fractal, and enables the user to de ne custom recon gurations using a simple imperative language.

Safe Dynamic Reconfigurations of Fractal Architectures with FScript

Today's software systems have to deal with an increasing diversity and complexity of execution environments. Next generation applications will have to deal with the unknown, with execution conditions which can not be predicted at the time they are written: they must be adaptable. In this paper, we present our current answer to this problem, in the form of an infrastructure for adaptable middleware. This infrastructure distinguishes functional components from non-functional services and enables dynamic reconfiguration of the associations between them. These associations are controlled by an adaptation engine which monitors both the execution environment and the application, and adapts the associations according to adaptation policies.

Pierre-Charles David

Papers

WildCAT: a generic framework for context-aware applications

An aspect-oriented approach for developing self-adaptive fractal components

FPath and FScript: Language support for navigation and reliable reconfiguration of Fractal architectures

Safe Dynamic Reconfigurations of Fractal Architectures with FScript

An Infrastructure for Adaptable Middleware