Remote method invocation as a first-class citizen

The classical remote method invocation (RMI) mechanism adopted by several object-based middleware is black-box in nature, and the RMI functionality, i.e., the RMI interaction policy and its configuration, is hard-coded into the application. This RMI nature hinders software development and reuse, forcing the programmer to focus on communication details often marginal to the application being developed. Extending the RMI behavior with extra functionality is also a very difficult job, because added code must be scattered among the entities involved in communications. This situation could be improved by developing the system in several separate layers, confining communications and related matters to specific layers. As demonstrated by recent work on reflective middleware, reflection represents a powerful tool for realizing such a separation and therefore overcoming the problems referred to above. Such an approach improves the separation of concerns between the communication-related algorithms and the functional aspects of an application. However, communications and all related concerns are not managed as a single unit that is separate from the rest of the application, which makes their reuse, extension, and management difficult. As a consequence, communications concerns continue to be scattered across the meta-program, communication mechanisms continue to be black-box in nature, and there is only limited opportunity to adjust communication policies through configuration interfaces. In this paper we examine the issues raised above, and propose a reflective approach specially designed to open up the RMI mechanism. Our proposal consists of a new reflective model, called multi-channel reification, that reflects on and reifies communication channels, i.e., it renders communication channels first-class citizens. This model is designed both for developing new communication mechanisms and for extending the behavior of communication mechanisms provided by the underlying system. Our approach is embodied in a framework called mChaRM, whisch is described in detail in this paper.Received: December 2001, Accepted: April 2003, Correspondence to: Walter Cazzola, c|o DISI, University of Genova, Via Dodecaneso 35. 16146, Genova, Italy. Fax + 39-010-353-6699)     

Applying techniques and tools for the performance engineering of SDL systems

The integration of performance evaluation techniques into the SDL method is an important task. In particular in the area of telecommunications and distributed systems where product families have to be maintained for many years, performance should be considered from the very beginning of system design. This paper demonstrates how performance engineering can be successfully applied. Firstly, an SDL specification of TCP/IP is used to derive a performance model that includes the original SDL system as well as additional constructs describing the consumption of time and resources. Different implementation variants have been evaluated in experimental scenarios. Secondly, the application of a specification-driven monitoring technique to the same SDL specification of TCP/IP is described. The case study shows how the functional and temporal behaviour of an implementation derived from an SDL specification can be analysed and improved by monitoring the running system. The two approaches, modelling and monitoring, are supplementary to each other. This paper provides arguments that the systematic application of specification-driven performance engineering will result in major savings of time and money in later development phases and for later system releases.     

实时CORBA规范分析与评述

实时系统是一类应用极为广泛的系统,而通用CORBA规范对实时应用支持不足,所以OMG制订了实时COR-BA1.0规范.。该规范支持固定优先级的实时CORBA应用,提供了实时CORBA应用中对象调用操作端到端的可预测性。文章对实时CORBA规范中所定义的控制和管理系统资源的策略和机制进行了较为详尽的阐述,并对其进行了分析与评述。     

Consolidating and applying the SDL-pattern approach: a detailed case study

This paper is on design methodology for communication systems. The SDL-pattern approach proposed recently is consolidated and applied rigorously and in detail to the design of a typical communication system on two levels of abstraction. The design is decomposed into a number of steps, each of which is carried out systematically, building on well-proven, generic pieces of solutions that have proven useful in previous projects. These generic solutions—termed SDL patterns—support reuse-driven design of communication systems, raise the vocabulary of protocol engineer to a problem-oriented level, assist the discovery and exploitation of commonalities, and lead to well-justified designs. The selection and use of SDL patterns is supported by a fine-grained incremental design process, the pattern definition takes advantage of formal design languages, and a set of heuristics addresses the decomposition of communication requirements. All these elements are presented and applied in detail to the design of a simple, but functionally complete communication system.     

Avoiding a middleware muddle

Middleware is a layer of software that enables communications between software components regardless of the programming language in which the components are developed, the protocols used to communicate between components, or the platforms on which the components execute. To make sense of the middleware morass and to select the middleware best for you, the author recommends the following steps when constructing your system: identify what type of communication must occur; identify the communications model you will use to implement that communication type; using your communications model, identify the types of middleware you will use to implement the communication; and evaluate candidate products. The author examines each step in detail     

Secure group communication schemes for dynamic heterogeneous distributed computing

Nowadays Sensor Networks and Ad Hoc Networks are widely used communication facilities, mainly because of their many application settings. Again, though above types of network are paradigms of communication widespread and well-established in the state of the art, however, they turn out to be among the most important concepts underlying the modern and increasingly expanding User-Centric Networks, which can be used to build dynamic middleware services for heterogeneous distributed computing. In this way, can be addressed the strong dynamic behavior of user communities and of resource collections they use.In this paper we focus our attention on key predistribution for secure communications in those types of networks. In particular, we first analyze some schemes proposed in the literature for enabling a group of two or more nodes to compute a common key, which can be used later on to encrypt or authenticate exchanged messages. The schemes we have chosen are well representative of different design strategies proposed in the state of the art. Moreover, in order to find out under which conditions and in which settings a scheme is more suitable than others, we provide an evaluation and a performance comparison of those schemes. Furthermore, we look at the problem of identifying optimal values for the parameters of such schemes, with respect to a certain desirable security degree and reasonable security assumptions. Finally, we extend one of those schemes, showing both analytically and through experiments, the improvement the new scheme provides in terms of security compared to the basic one.     

RFID中间件及其仓储管理的应用

现阶段RFID技术发展迅速，在物流仓储、商品防伪、交通运输、医疗卫生、国防军事等方面得到了广泛应用。但是由于将RFID设备与企业后端系统（如：SCM系统、ERP系统）之间的整合耗费不菲且技术复杂，制约了RFID技术的推广。近来RFID中间件的推出很好地解决了技术与成本这两方面问题，加速了RFID技术的推广使用。该文在介绍RFID（射频识别）技术的组成及其特点的基础上，研究了RFID中间件架构，并提出了一个基于IBM RFID中间件开发的仓储管理系统的设计方法。     

Scalable networked information processing environment (SNIPE)

Scalable Networked Information Processing Environment (SNIPE) is a metacomputing system that aims to provide a reliable, secure, fault-tolerant environment for long-term distributed computing applications and data stores across the global Internet. This system combines global naming and replication of both processing and data to support large-scale information processing applications leading to better availability and reliability than currently available with typical cluster computing and/or distributed computer environments. To facilitate this the system supports: distributed data collection, distributed computation, distributed control and resource management, distributed output and process migration. The underlying system supports multiple communication paths, media and routing methods to aid performance and robustness across both local and global networks. This paper details the goals, design and an initial implementation of SNIPE, and then demonstrates its usefulness in supporting a middleware project. Initial communications performance is also presented.     

基于XML和Reactor模式的消息中间件的设计

在复杂的分布式计算环境中,中间件已经成为分布式计算应用的关键性部件。本文设计实现了一个基于消息队列的消息中间件系统,用于集成分布式应用,提供可靠的和松耦合的通信服务。系统采用XML定义消息,统一了消息格式;采用Reactor设计模式,提高了系统的模块化和可重用性。     

一种发布订阅中间件的设计

设计一种基于主题发布订阅机制的中间件。发布/订阅机制能够提供一对多和多对多的异步通信模式,能使通信的各个参与者在时间和空间上完全解耦,能很好地满足大规模分布式系统松耦合通信的需求。对该中间件的网络数据传输延迟作测试。     

POSAML: A visual modeling language for middleware provisioning

Next generation distributed applications are often hosted on heterogeneous platforms including different kinds of middleware. Due to the applications’ growing functional complexity and their multiple quality of service (QoS) requirements, system developers are increasingly facing a substantial number of middleware provisioning challenges, which include configuring, optimizing and validating the middleware platforms for QoS properties. Traditional techniques for middleware provisioning tend to use non-intuitive, low-level and technology-specific approaches, which are tedious, error prone, and non-reusable across different technologies. Quite often the middleware provisioning activities are carried out by different actors without much interaction among them, which results in an iterative trial-and-error process to provisioning. Higher level abstractions, particularly those that use visual models, are effective in addressing these challenges. This paper describes the design of a visual modeling language called POSAML (pattern-oriented software architecture modeling language) and associated tools that provide an intuitive, higher level and unified framework for provisioning middleware platforms. POSAML provides visual modeling capabilities for middleware-independent configurations and optimizations while enabling automated middleware-specific validation of system QoS properties.     

一种基于中间件的容错系统的研究与设计

随着硬件容错技术的成熟，软件容错技术成为提高系统可靠性的热点问题。直接开发容错应用是非常困难的，鉴于中间件为应用系统提供了良好的开发环境，该文研究和设计了一个基于中间件的容错系统模型，提出了一种新的节点容错结构构造方法，为解决冗余、失效检测和恢复等容错的关键技术问题形成了一套较完整的解决方案。采用马尔科夫过程求出系统的可靠度，验证了系统设计的合理性和可靠性。     

A Survey of Fault Management in Wireless Sensor Networks

Wireless sensor networks are resource-constrained self-organizing systems that are often deployed in inaccessible and inhospitable environments in order to collect data about some outside world phenomenon. For most sensor network applications, point-to-point reliability is not the main objective; instead, reliable event-of-interest delivery to the server needs to be guaranteed (possibly with a certain probability). The nature of communication in sensor networks is unpredictable and failure-prone, even more so than in regular wireless ad hoc networks. Therefore, it is essential to provide fault tolerant techniques for distributed sensor applications. Many recent studies in this area take drastically different approaches to addressing the fault tolerance issue in routing, transport and/or application layers. In this paper, we summarize and compare existing fault tolerant techniques to support sensor applications. We also discuss several interesting open research directions. Lilia Paradis is currently a graduate student in the Department of Mathematical and Computer Sciences, Colorado School of Mines. She is also part of the Toilers Ad Hoc Networking research group. She is interested in distributed communication protocols for wireless sensor networks. Qi Han received the PhD degree in computer science from the University of California, Irvine in 2005. She is currently an assistant professor in the Department of Mathematical and Computer Sciences, Colorado School of Mines. Her research interests include distributed systems, middleware, mobile and pervasive computing, systems support for sensor applications, and dynamic data management. She is specifically interested in developing adaptive middleware techniques for next generation distributed systems. She is a member of the IEEE and the ACM.     

A middleware architecture to facilitate distributed programming: DAROC: Data-Activated Replicated Object Communications

Programming distributed computer systems is difficult because of complexities in addressing remote entities, message handling, and program coupling. As systems grow, scalability becomes critical, as bottlenecks can serialize portions of the system. When these distributed system aspects are exposed to programmers, code size and complexity grow, as does the fragility of the system. This paper describes a distributed software architecture and middleware implementation that combines object-based blackboard-style communications with data-driven and periodic application scheduling to greatly simplify distributed programming while achieving scalable performance. Data-Activated Replication Object Communications (DAROC) allows programmers to treat shared objects as local variables while providing implicit communications.     

Verifying distributed real-time properties of embedded systems via graph transformations and model checking

Component middleware provides dependable and efficient platforms that support key functional, and quality of service (QoS) needs of distributed real-time embedded (DRE) systems. Component middleware, however, also introduces challenges for DRE system developers, such as evaluating the predictability of DRE system behavior, and choosing the right design alternatives before committing to a specific platform or platform configuration. Model-based technologies help address these issues by enabling design-time analysis, and providing the means to automate the development, deployment, configuration, and integration of component-based DRE systems. To this end, this paper applies model checking techniques to DRE design models using model transformations to verify key QoS properties of component-based DRE systems developed using Real-time CORBA. We introduce a formal semantic domain for a general class of DRE systems that enables the verification of distributed non-preemptive real-time scheduling. Our results show that model-based techniques enable design-time analysis of timed properties and can be applied to effectively predict, simulate, and verify the event-driven behavior of component-based DRE systems. This research was supported by the NSF Grants CCR-0225610 and ACI-0204028 Gabor Madl is a Ph.D. student and a graduate student researcher at the Center for Embedded Computer Systems at the University of California, Irvine. His advisor is Nikil Dutt. His research interests include the formal verification, optimization, component-based composition, and QoS management of distributed real-time embedded systems. He received his M.S. in computer science from Vanderbilt University and in computer engineering from the Budapest University of Technology and Economics. Dr. Sherif Abdelwahed received his Ph.D. degree in Electrical and Computer Engineering from the University of Toronto, Canada, in 2001. During 2000–2001, he was a research scientist with the system diagnosis group at the Rockwell Scientific Company. Since 2001 he has been with the Department of Electrical Engineering and Computer Science at Vanderbilt University as a Research Assistant Professor. His research interests include verification and control of distributed real-time systems, and model-based diagnosis of discrete-event and hybrid systems. Dr. Douglas C. Schmidt is a Professor of Computer Science, Associate Chair of the Computer Science and Engineering program, and a Senior Researcher in the Institute for Software Integrated Systems (ISIS) all at Vanderbilt University. He has published over 300 technical papers and 6 books that cover a range of research topics, including patterns, optimization techniques, and empirical analyses of software frameworks and domain-specific modeling environments that facilitate the development of distributed real-time and embedded (DRE) middleware and applications. Dr. Schmidt has served as a Deputy Office Director and a Program Manager at DARPA, where he lead the national R&D effort on middleware for DRE systems. In addition to his academic research and government service, Dr. Schmidt has over fifteen years of experience leading the development of ACE, TAO, CIAO, and CoSMIC, which are widely used, open-source DRE middleware frameworks and model-driven tools that contain a rich set of components and domain-specific languages that implement patterns and product-line architectures for high-performance DRE systems.     

Designing on‐demand education for simultaneous development of domain‐specific and self‐directed learning skills

On‐demand education enables individual learners to choose their learning pathways according to their own learning needs. They must use self‐directed learning (SDL) skills involving self‐assessment and task selection to determine appropriate pathways for learning. Learners who lack these skills must develop them because SDL skills are prerequisite to developing domain‐specific skills. This article describes the design of an on‐demand learning environment developed to enable novices to simultaneously develop their SDL and domain‐specific skills. Learners received advice on their self‐assessments and their selections of subsequent learning tasks. In the domain of system dynamics – a way to model a dynamic system and draw graphs depicting the system's behaviour over time – advice on self‐assessment is provided in a scoring rubric containing relevant performance standards. Advice on task selection indicates all relevant task aspects to be taken into account, including recommendations for suitable learning tasks which meet the individual learner's needs. This article discusses the design of the environment and the learners' perceptions of its usefulness. Most of the times, the learners found the advice appropriate and they followed it in 78% of their task selections.     

An approach to domain-based scalable context management architecture in pervasive environments

In pervasive environments, context management systems are expected to administrate large volume of contextual information that is captured from spatial to nonspatial elements. Research in context-aware computing produced a number of middleware systems for context management to intermediate the communications between applications and context providers. In particular, in pervasive environments, the design of distributed storage, retrieval and propagation mechanisms of context information across domains is vital. In this paper, we propose a domain-based approach to address the requirements of scalable distributed context management, cross-domain efficient context information dissemination and domain-based privacy policy enforcement. We propose infinitum, a middleware architecture that incorporates the management and communication benefits of the Google Wave Federation Protocol, while also taking advantage of the semantic and inference benefits of ontology-based context models. This architecture establishes a robust cross-domain scalable context management and collaboration framework, which has been implemented and evaluated in a real-life application of “SMART University” to support virtual team collaboration.     

MESHMdl event spaces — A coordination middleware for self-organizing applications in ad hoc networks

Mobile ad hoc networks (MANETs) are gaining importance as a promising technology for flexible, proximity-based, mobile communication. However, the inherent dynamics of MANETs imposes strong limitations on the design of distributed applications. They need to be able to adapt to changing conditions quickly and organize themselves in terms of component placement and communication habits. In this paper, we present MESHMdl, a middleware that provides a high level of awareness and decoupling for application components to make them more flexible and adaptable. We focus on the Event Space as the central communication medium of MESHMdl. The Event Space offers a simple, unified communication interface for inter-agent communication as well as for communication with the middleware and resource access. Furthermore, it serves as a means for flexibly extending a MESHMdl daemon. We investigate the performance of the Event Space on different mobile devices and show that it is superior to comparable systems.