Abstract. Aspect-Oriented Programming (AOP) and Component-Based Software Engineering (CBSE) offer solutions to improve the separation of concerns and to enhance a program structure. If the integration of AOP into CBSE has already been proposed, none of these solutions focus on the application of CBSE principles to AOP. In this paper we propose a twofold integration of AOP and CBSE. We introduce a general model for components and aspects, named Fractal Aspect Component (FAC). FAC decomposes a software system into regular components and aspect components (ACs), where an AC is a regular component that embodies a crosscutting concern. We reify the aspect domain of an AC and the relationship between an AC and a component, called an aspect binding, as first-class runtime entities. This clarifies the architecture of a system where components and aspects coexist. The system can evolve from the design to the execution by adding or removing components, aspects or bindings. 1

The paper introduces a higher-order synchronous data-flow language in which communication channels may themselves transport programs. This provides a mean to dynamically reconfigure data-flow processes. The language comes as a natural and strict extension of both Lustre and Lucid Synchrone. This extension is conservative, in the sense that a first-order restriction of the language can receive the same semantics. We illustrate the expressivity of the language with some examples, before giving the formal semantics of the underlying calculus. The language is equipped with a polymorphic type system allowing types to be automatically inferred and a clock calculus rejecting programs for which synchronous execution cannot be statically guaranteed. To our knowledge, this is the first higher-order synchronous data-flow language where stream functions are first class citizens. Categories and Subject Descriptors C.3 [Special-purpose and application-based systems]: Real-time and embedded systems; D.3.2 [Language classifications]: Data-flow languages; F.3.2 [Semantics of programming languages]: Operational semantics.

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

Model checking of isolated software components is inherently not possible because a component does not form a complete program with an explicit starting point. To overcome this obstacle, it is typically necessary to create an environment of the component which is the intended subject to model checking. We present our approach to automated environment generation that is based on behavior protocols [9]; to our knowledge, this is the only environment generator designed for model checking of software components. We compare it with the approach taken in the Bandera Environment Generator tool [12], designed for model checking of sets of Java classes.

Abstract. A software component model should define what components are, and how they can be composed. That is, it should define a theory of components and their composition. Current software component models tend to use objects or port-connector type architectural units as components, with method calls and port-to-port connections as composition mechanisms. However, these models do not provide a proper composition theory, in particular for key underlying concepts such as encapsulation and compositionality. In this paper, we outline our notion of these concepts, and give a preliminary formalisation of a software component model that embodies these concepts. 1

Abstract. This paper presents AOKell, a framework for engineering component-based systems. This framework implements the Fractal model, a hierarchical and dynamic component model. The novelty of this paper lies in the presentation of AOKell, an implementation of the Fractal model with aspects. Two dimensions can be isolated with Fractal: the functional dimension, which is concerned with the definition of application components, and the control dimension, which is concerned with the technical services (e.g. lifecycle, binding, persistence, etc.) that manage components. The originality of AOKell is, first, to provide an aspect-oriented approach to integrate these two dimensions, and second, to apply a component-based approach for engineering the control dimension. Hence, AOKell is a reflective component framework where application components are managed by other, so-called, control components and where aspects glue together application components and control components. 1

Abstract. An architectural aspect is a concern that cuts across architecture modularity units and cannot be effectively modularized using the given abstractions of conventional Architecture Description Languages (ADLs). Dealing with crosscutting concerns is not a trivial task since they affect each other and the base architectural decomposition in multiple heterogeneous ways. The lack of ADL support for modularly representing such aspectual heterogeneous influences leads to a number of architectural breakdowns, such as increased maintenance overhead, reduced reuse capability, and architectural erosion over the lifetime of a system. On the other hand, software architects should not be burdened with a plethora of new ADL abstractions directly derived from aspect-oriented implementation techniques. However, most aspect-oriented ADLs rely on a heavyweight approach that mirrors programming languages concepts at the architectural level. In addition, they do not naturally support heterogeneous architectural aspects and proper resolution of aspect interactions. This paper presents AspectualACME, a simple and seamless extension of the ACME ADL to support the modular representation of architectural aspects and their multiple composition forms. AspectualACME promotes a natural blending of aspects and architectural abstractions by employing a special kind of architectural connector, called Aspectual Connector, to encapsulate aspect-component connection details. We have evaluated the applicability and scalability of the AspectualACME features in the context of three case studies from different application domains.

This paper presents a component-based architecture for autonomous repair management in distributed systems, and a prototype implementation of this architecture, called JADE, which provides repair management for J2EE application server clusters. The JADE architecture features three major elements, which we believe to be of wide relevance for the construction of autonomic distributed systems: (1) a dynamically configurable, component-based structure that exploits the reflective features of the FRACTAL component model; (2) an explicit and configurable feedback control loop structure, that manifests the relationship between managed system and repair management functions; (3) an original replication structure for the management subsystem itself, which makes it fault-tolerant and self-healing. 1

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This article presents a component verification platform called Vercors providing means to analyse the behaviour properties of applications built from distributed components. From the behavioural specification of primitive components, and from the architectural description of the composite components, our tools build models encoding the interactions between the components, suitable for analysis by model-checking tools. The models are hierarchical and parameterized, expressing in a compact way the system behaviour. Then we have tools for instantiating those parameterized models using finite abstractions, and producing input for state-of-the-art verification tools. Our current work also targets the generation of models that include controllers modelling the dynamic management of architectural transformation of an application, such as changes in bindings or replacement of sub-components. We describe the existing tools, give tracks for further developments and show how realistic case-studies can be model-checked using our platform.