Agent-oriented techniques represent an exciting new means of analysing, designing and building complex software systems. They have the potential to significantly improve current practice in software engineering and to extend the range of applications that can feasibly be tackled. Yet, to date, there have been few serious attempts to cast agent systems as a software engineering paradigm. This paper seeks to rectify this omission. Specifically, it will be argued that: (i) the conceptual apparatus of agent-oriented systems is well-suited to building software solutions for complex systems and (ii) agent-oriented approaches represent a genuine advance over the current state of the art for engineering complex systems. Following on from this view, the major issues raised by adopting an agent-oriented approach to software engineering are highlighted and discussed. 1.

This paper describes work in progress to develop a standard for interoperability among high-performance scientific components. This research stems from growing recognition that the scientific community needs to better manage the complexity of multidisciplinary simulations and better address scalable performance issues on parallel and distributed architectures. Driving forces are the need for fast connections among components that perform numerically intensive work and for parallel collective interactions among components that use multiple processes or threads. This paper focuses on the areas we believe are most crucial in this context, namely, an interface definition language that supports scientific abstractions for specifying component interfaces and a ports connection model for specifying component interactions.

In this paper, the authors address some of the challenges of the current technologies in the area of component-based programming and automated software downloading. These challenges include: component updating at runtime of affected applications, adopting the "true-push" model in order to allow for silent software modification (e.g. for removing minor implementation errors), and finding a way to integrate these technologies and electronic commerce in software components. To respond to these challenges, the SOFA (SOFtware Appliances) architecture, the SOFA component model and its extension, DCUP (Dynamic Component UPdating), are introduced. SOFA and DCUP provide a small set of well scaling orthogonal abstractions which address three areas: the background for electronic commerce, the component model, and support for dynamic component updating in running applications. The updating granularity can scale anything from minor implementation changes to a major reconfiguration. In contrast with the usual belief that it is difficult to map abstractions supporting component based programming to concrete computer systems, the abstractions proposed by DCUP are very easy to map to the Java and CORBA programming environments.

We present Jiazzi, a system that enables the construction of largescale binary components in Java. Jiazzi components can be thought of as generalizations of Java packages with added support for external linking and separate compilation. Jiazzi components are practical because they are constructed out of standard Java source code. Jiazzi requires neither extensions to the Java language nor special conventions for writing Java source code that will go inside a component. Our components are expressive because Jiazzi supports cyclic component linking and mixins, which are used together in an open class pattern that enables the modular addition of new features to existing classes. This paper describes Jiazzi, how it enhances Java with components, its implementation, and how type checking works. An implementation of Jiazzi is available for download.

The ability of performance technology to keep pace with the growing complexity of parallel and distributed systems depends on robust performance frameworks that can at once provide system-specific performance capabilities and support high-level performance problem solving. Flexibility and portability in empirical methods and processes are influenced primarily by the strategies available for instrumentation and measurement, and how effectively they are integrated and composed. This paper presents the TAU (Tuning and Analysis Utilities) parallel performance system and describe how it addresses diverse requirements for performance observation and analysis.

In this paper we introduce a novel aspect oriented implementation language, called JAsCo. JAsCo is tailored for component based development and the Java Beans component model in particular. The JAsCo language introduces two concepts: aspect beans and connectors. An aspect bean describes behavior that interferes with the execution of a component by using a special kind of inner class, called a hook. The specification of a hook is context independent and therefore reusable. A connector on the other hand, is used for deploying one or more hooks within a specific context. To implement the JAsCo language, we propose a new “aspect-enabled ’ component model, which contains build-in traps that enable to interfere with the normal execution of a component. The JAsCo component model is backward-compatible with the Java Beans component model. Furthermore, the JAsCo component model allows very flexible aspect application, adaptation and removal at run-time. The necessary tool support for the JAsCo approach has been implemented. In addition, we present a performance assessment of our current implementation. 1.

Middleware has emerged as an important architectural component in modern distributed systems. Most recently, industry has witnessed the emergence of component-based middleware platforms, such as Enterprise JavaBeans and the CORBA Component Model, aimed at supporting third party development, configuration and subsequent deployment of software. The goals of our research is to extend this work in order to exploit the benefits of component-based approaches within the middleware platform as well as on top of the platform, the result being more configurable and reconfigurable middleware technologies. This is

Event-based systems are developed and used to integrate components in loosely coupled systems. Research and product development focused so far on e#ciency issues but neglected methodological support to build such systems. In this article, the modular design and implementation of an event system is presented which supports scopes and event mappings, two new and powerful structuring methods that facilitate engineering and coordination of components in event-based systems. We give a

We identify three programming language abstractions for the construction of reusable components: abstract type members, explicit selftypes, and modular mixin composition. Together, these abstractions enable us to transform an arbitrary assembly of static program parts with hard references between them into a system of reusable components. The transformation maintains the structure of the original system. We demonstrate this approach in two case studies, a subject/observer framework and a compiler front-end.

Web services are becoming the prominent paradigm for distributed computing and electronic business. This has raised the opportunity for service providers and application developers to develop valueadded services by combining existing web services. Emerging web service standards and web service composition solutions have not addressed the issues of service re-use and extension yet. In this paper we propose the concept of web component that packages together elementary or complex services and presents their interfaces and operations in a consistent and uniform manner in the form of a class definition. Web components are internally synthesized out of reused, specialized, or extended elementary or complex web services. They are published externally as normal web services and can thus be employed by any web-based application. 1