Grid enabled portals are becoming increasingly popular as a platform for providing access to Grid services and resources. Unfortunately, much of the work done in portal development has led to vertically layered solutions that work for a particular project but are difficult to extend or reuse for other projects. The Grid-Sphere portal framework seeks to address these limitations by providing a framework that will offer external developers a model for easily adding new functionality and hence increasing community collaboration. The GridLab portal will serve as an initial prototype to showcase the GridSphere framework and provide access to services being developed within the GridLab project. 1

High-performance Web servers are essential to meet the growing demands of the Internet and large-scale intranets. Satisfying these demands requires a thorough understanding of key factors affecting Web server performance. This paper presents empirical analysis illustrating how dynamic and static adaptivity can enhance Web server performance. Two research contributions support this conclusion. First, the paper presents results from a comprehensive empirical study of Web servers (such as Apache, Netscape Enterprise, PHTTPD, Zeus, and JAWS) over high-speed ATM networks. This study illustrates their relative performance and precisely pinpoints the server design choices that cause performance bottlenecks. We found that once network and disk I/O overheads are reduced to negligible constant factors, the main determinants of Web server performance are its protocol processing path and concurrency strategy. Moreover, no single strategy performs optimally for all load conditions and traffic type...

Distributed object computing forms the basis of nextgeneration communication software. At the heart of distributed object computing are Object Request Brokers (ORBs), which automate many tedious and error-prone distributed programming tasks. Like much communication software, conventional ORBs use statically configured designs, which are hard to port, optimize, and evolve. Likewise, conventional ORBs cannot be extended without modifying their source code, which forces recompilation, relinking, and restarting running ORBs and their associated application objects. This paper makes two contributions to the study of extensible ORB middleware. First, it presents a case study illustrating how a pattern language can be used to develop dynamically configurable ORBs that can be customized for specific application requirements and system characteristics. Second, we quantify the impact of applying this pattern language to reduce the complexity and improve the maintainability of common ORB tasks, ...

Developers of communication software face many challenges. Communication software contains both inherent complexities, such as fault detection and recovery, and accidental complexities, such as the continuous re-rediscovery and re-invention of key concepts and components. Meeting these challenges requires a thorough understanding of object-oriented application frameworks and patterns. This paper illustrates how we have applied frameworks and patterns for communication software to develop a high-performance Web server called JAWS. JAWS is an object-oriented framework that supports the configuration of various Web server strategies, such as a Thread Pool concurrency model with asynchronous I/O and LRU caching vs.. a Thread-per-Request concurrency model with synchronous I/O and LFU caching. Because JAWS is a framework, these strategies can be customized systematically and measured both independently and collaboratively to determine the best strategy profiles. Using these profiles, JAWS can statically and dynamically adapt its behavior to deploy the most effective strategies for a given software/hardware platform and workload. JAWS ’ adaptive software features make it a powerful application framework for constructing highperformance Web servers. 1

Developers of mission-critical distributed real-time and embedded (DRE) systems face a fundamental tension between (1) the performance gains achievable with hand-crafted optimizations to systems built largely from scratch and (2) the development cost and cycle-time reductions offered by common off-the-shelf (COTS) middleware. This paper describes how the Kokyu portable middleware scheduling framework, which is built using standards-based COTS middleware and OS primitives, can be used both to (1) maintain the flexibility and reuse offered by COTS middleware and (2) provide opportunities for domain-specific optimizations that are needed to meet stringent real-time performance requirements.

this paper significantly.

Real-time systems and applications impose stringent timing constraints on critical tasks. The design of such systems are more complex than that of conventional systems, because correctness and performance, besides being key system design issues, are directly related to system feasiblility. Object-oriented application frameworks have been proposed for communication systems, distributed applications, medical imaging, and financial engineering. On the contrary, there has been relatively little work on an application framework for the design of a general real-time system. Facing the growing need for such systems, we propose a novel framework, called RTFrame, especially for real-time systems. RTFrame consists of five components: Specifier, Extractor, Scheduler, Allocator, and Generator. Within RTFrame, several design patterns have been proposed for real-time systems. Experiences of using RTFrame show a significant increase in design productivity through design reuse, and a significant decrease in design time and effort. 1

Developers of communication applications must address recurring design challenges related to efficiency, extensibility, and robustness. These challenges are often independent of application-specific requirements. Successful developers resolve these challenges by applying appropriate patterns and pattern languages. Traditionally, however, these patterns have been locked in the heads of expert developers or buried deep within complex system source code. The primary contribution of this paper is to describe a pattern language that underlies object-oriented communication software. In addition to describing each pattern in this language, the paper illustrates how knowledge of the relationships and trade-offs among the patterns helps guide the construction of reusable communication frameworks and applications. 1 Introduction Communication software is the set of services and protocols that makes possible modern distributed systems and applications, such as web services, distributed objects,...

n of simulation models, distributed heterogeneous execution, and dynamic multimedia documentation, has the potential to meet these requirements. This paper outlines the current aircraft design process, highlighting its problems and complexities, and presents our vision of an aircraft design process using Web-based modeling and simulation. Categories and Subject Descriptors: I.6.5 [Simulation Modeling]: Model Developmentmodeling methodologies; I.6.8 [Simulation Modeling]: Types of Simulationdistributed General Terms: Design Additional Key Words and Phrases: Web-based simulation, aircraft design, Java, object-oriented 1. INTRODUCTION Intensive competition in the commercial aviation industry is placing increasing pressure on aircraft manufacturers to reduce the time, cost and risk of product development. To compete effectively in today's global marketplace, innovative approaches to reducing

Software engineering aims at techniques for producing better software products with less resources. A central concept for achieving this goal is a product line architecture. Frameworks are a popular object-oriented way to implement product line architectures. However, frameworks are often difficult to learn and their specializations consist of small and crosscutting logical entities that overlap with other design solutions of the software product. Implementation becomes fragmented, difficult to trace, and the original reasoning of the design is easily forgotten. Thus, the essential problems to be solved are the following: • How to teach the software developer to understand different frameworks and design principles in the context of her software product? • How to guide the software developer to use frameworks and product line architectures? • How to maintain and document implemented design solutions and framework specializations? In this