Policy driven management for distributed systems

Separating management policy from the automated managers which interpret the policy facilitates the dynamic change of behavior of a distributed management system. This permits it to adapt to evolutionary changes in the system being managed and to new application requirements. Changing the behavior of automated managers can be achieved by changing the policy without having to reimplement them—this permits the reuse of the managers in different environments. It is also useful to have a clear specification of the policy applying to human managers in an enterprise. This paper describes the work on policy which has come out of two related ESPRIT funded projects, SysMan and IDSM. Two classes of policy are elaborated—authorization policies define what a manager is permitted to do and obligation policies define what a manager must do. Policies are specified as objects which define a relationship between subjects (managers) and targets (managed objects). Domains are used to group the objects to which a policy applies. Policy objects also have attributes specifying the action to be performed and constraints limiting the applicability of the policy. We show how a number of example policies can be modeled using these objects and briefly mention issues relating to policy hierarchy and conflicts between overlapping policies.     

Large scale interoperability and distributed transaction processing

This article integrates an interoperability architecture, the OSCA^TM architecture, and a distributed transaction processing protocol, the X/Open^® Distributed Transaction Processing model, into a unified model of large scale interoperability and distributed transaction processing. Applications supporting different business operations are often deployed in heterogeneous environments in which applications are stand alone islands and operations are fragmented. But in order to have integrated operations, a loosely coupled system of autonomous applications is required often bound together via a distributed transaction processing protocol. This article describes a model for this configuration. It will propose that the span of control of a transaction manager defines the transaction environment for a single application. Any two applications need not conform to the same supplier's transaction environment nor reside in the same environment. Interoperability must be provided among applications, since any one application cannot assume that any other application is under the control of the same transaction manager. Requirements are imposed upon the interactions of applications to support interoperability. The interface between transaction managers must be compatible with these requirements. Other distributed architecture standards must define the requirements for release independence, resource independence, accessibility transparency, location transparency, contract interfaces, and secure environment.     

Managing Quality-of-Service in Internet Applications Using Differentiated Services

Advances in networks during the past decades have fostered the deployment of a variety of Internet applications. Many of these applications have a range of Quality-of-Service (QoS) requirements, some involving network throughput, delay, and reliability. Consequently, there is growing need for network services that can differentiate applications having QoS requirements from those without and to be able to further classify applications with QoS requirements into different classes at the IP-network level. The Internet Engineering Task Force (IETF) has proposed Differentiated Services (DiffServ) to provide QoS in IP-based networks. The goal of DiffServ is to define configurable types of packet forwarding that can provide service differentiation for large aggregates of network traffic. We report on our investigation of Relative Proportional Differentiated Services to implement DiffServ in IP-based networks and one that supports the provisioning and management of QoS for Internet Applications. The main contributions of the paper are the introduction of a novel traffic conditioning architecture for the marker and shaper/policer which relies on feedback from a metering component, and the provision for a QoS manager to enable a network administrator or a management application to dynamically adjust control parameters.     

PESOI： Process Embedded Service-Oriented Architecture

1 Introduction Service-Oriented Architecture (SOA) has received significant attention recently as major computer and software companies such as HP, IBM, Intel, Microsoft, and SAP, have all embraced SOA, as well as government agencies such as DoD (US depar…     

A framework for low energy data management in reconfigurable multi-context architectures

In this paper, we present an approach to the problem of low energy data scheduling for reconfigurable architectures targeting digital signal processing (DSP) and multimedia applications. The main goal is the reduction of the energy consumed by these applications through the integration of the proposed data management framework within a compilation tool specifically conceived for these architectures. Two levels of on-chip data storage are assumed to be available in the reconfigurable architecture. Then, the data manager tries to optimally exploit this storage hierarchy by saving data transfers among on-chip and external memories, so reducing the energy consumption. To do that, specific algorithms for finding the data shared among the different computation kernels of the application have been developed. Also, a data placement and replacement policy has been designed. We also show how an adequate data scheduling could decrease the number of operations required to implement the dynamic reconfiguration of the system.     

A domain-specific software architecture for adaptive intelligentsystems

A good software architecture facilitates application system development, promotes achievement of functional requirements, and supports system reconfiguration. We present a domain-specific software architecture (DSSA) that we have developed for a large application domain of adaptive intelligent systems (AISs). The DSSA provides: (a) an AIS reference architecture designed to meet the functional requirements shared by applications in this domain, (b) principles for decomposing expertise into highly reusable components, and (c) an application configuration method for selecting relevant components from a library and automatically configuring instances of those components in an instance of the architecture. The AIS reference architecture incorporates features of layered, pipe and filter, and blackboard style architectures. We describe three studies demonstrating the utility of our architecture in the subdomain of mobile office robots and identify software engineering principles embodied in the architecture     

一种面向普适计算的自适应软件平台的设计与实现

普适计算的适应性特征带来了有必要在软件平台层面解决的一系列共性问题,包括如何定义所支持的自适应软件体系结构、如何为上层应用的自适应提供必要的公共服务、如何使平台自身可以适应多维资源受限环境等。针对这些挑战,提出了对普适计算设备/资源进行适应性抽象的自主单元的概念,在此基础上给出了面向普适计算的自适应软件平台UbiStar的系统架构及其核心机制的设计与实现,并对UbiStar平台对适应性软件所提供的支持机制进行了概括,最后对相关工作进行了分析与比较。     

面向Agent的软件设计模式

设计模式针对一类在特定上下文中反复出现的问题给出了通用解决方案,模式的提取和重用有助于提高软件开发的效率和质量,其思想和方法已在面向对象软件工程中得到广泛应用和验证。我们认为同一问题采用不同的实现技术往往具有不同的设计形态,不同软件开发范型也有其各自不同的设计模式。作为一种新颖的软件开发范型,近年来面向Agent软件工程的研究取得了长足进展,如何提高软件Agent技术实用性,发挥其技术潜力,扩大其应用范围成为当前人们关注的焦点。本文将模式思想引入到面向Agent软件工程,针对软件Agent技术的特点,从组织结构、交互协作和个体Agent体系结构三个视点提出了一组面向Agent的软件设计模式,以支持多Agent系统的设计;并进一步给出了面向Agent设计模式的描述框架,进行了典型设计模式和应用案例的分析。     

Distributed,application-level monitoring for heterogeneous clouds using stream processing

As utility computing is widely deployed, organizations and researchers are turning to the next generation of cloud systems: federating public clouds, integrating private and public clouds, and merging resources at all levels (IaaS, PaaS, SaaS). Adaptive systems can help address the challenge of managing this heterogeneous collection of resources. While services and libraries exist for basic management tasks that enable implementing decisions made by the manager, monitoring is an open challenge. We define a set of requirements for aggregating monitoring data from a heterogeneous collections of resources, sufficient to support adaptive systems. We present and implement an architecture using stream processing to provide near-realtime, cross-boundary, distributed, scalable, fault-tolerant monitoring. A case study illustrates the value of collecting and aggregating metrics from disparate sources. A set of experiments shows the feasibility of our prototype with regard to latency, overhead, and cost effectiveness.     

基于指纹识别的网络身份认证系统

指纹识别技术已经广泛地应用于公安、银行、证券等机关、企事业单位。介绍了指纹识别技术及其在身份认证方面的应用,提出了基于指纹识别的网络身份认证系统的一种解决方案,给出了系统的拓扑结构和软件体系结构。该系统针对不同的领域配以不同的应用软件,可应用于远程网络数据库的访问权限及身份的确认等,以提高网上业务活动的安全性。     

A Tiered System for Serving Differentiated Content

Contemporary Web sites typically consist of front–end Web servers, application servers, and back-end information systems such as database servers. There has been limited research on how to provide overload control and service differentiation for the back-end systems. In this paper we propose an architecture called tiered service (TS) for these purposes. In TS, there are several heterogeneous back-end systems to serve the Web applications. The Web applications communicate with a routing intermediary to intelligently route the queries to the appropriate back-end servers based on various policies such as client profiles and server load. In our system the back ends may store different qualities of data; lower quality data typically requires less overhead to serve. The main contributions of this paper include (i) a tiered content replication scheme that replicates tiered qualities of data on heterogeneous back ends with different capacity to satisfy clients with diverse requirements for latency and quality of data, and (ii) an application-transparent query routing architecture that automatically routes the queries to the appropriate back ends. The architecture was implemented in our test bed, and its performance was benchmarked. The experimental results demonstrate that TS offers significant performance improvement.     

An integration experience of a software architecture and a monitoring infrastructure to deploy applications with non‐functional requirements in computing grids

Resource management is an important aspect to consider regarding applications that might have different non‐functional or operational requirements, when running in distributed and heterogeneous environments. In this context, it is necessary to provide the means to specify the required resource constraints and an infrastructure that can adapt the applications in light of the changes in resource availability. We adopted a contract‐based approach to describe and maintain parallel applications that have non‐functional requirements in a Computing Grid context, called ZeliGrid. To form the supporting infrastructure we have designed a software architecture that integrates some of the Globus services, the LDAP and the NWS monitoring services. Some modules that map the contract approach into software artifacts were also integrated to this architecture. This paper addresses the architecture and integration issues of our approach, as well as how we put the pieces together highlighting deployment and implementation details, which have to consider diverse aspects such as monitoring, security and dynamic reconfiguration. Copyright © 2010 John Wiley & Sons, Ltd.     

Salespoint: A Java framework for teaching object-oriented software development

Teaching systematic object-oriented software development to undergraduate students is difficult: Students need to develop a lot of complex skills. These include technical skills in object-oriented software development, but also social skills—for example, how to collaborate with other developers as part of a team working towards a large and complex software system. To acquire these skills, students need hands-on development experiences—for example, through team-oriented project courses. Designing such project courses is a challenge in itself: They must be both sufficiently challenging and achievable within the limited time available. In our special situation (large numbers of students supervised by small numbers of staff) an important further requirement is scalability: Different projects should be easily comparable while allowing for different tasks for different teams to reduce the risk of plagiarism. The solution that in our experience satisfies all these requirements is to use an application framework for an everyday application domain—for example, the business domain.Since 1997, we have been using Salespoint, a Java-based framework for creating business applications, that has been jointly developed and maintained in Dresden and Munich. In this paper, we briefly recollect the educational background and aims of the courses and present in some detail Salespoint (and its most recent revision, Salespoint2010): central notions like catalogs and stocks, the functionality it offers to users (application control, data management, and much more), a technical overview of its architecture, an example application built with Salespoint, and some lessons learned so far.     

A model-driven approach for the derivation of architectural requirements of software product lines

The alignment of the software architecture and the functional requirements of a system is a demanding task because of the difficulty in tracing design elements to requirements. The four-step rule set (4SRS) is a unified modeling language (UML)-based model-driven method for single system development which provides support to the software architect in this task. This paper presents an evolution of the 4SRS method aimed at software product lines. In particular, we describe how to address the transformation of functional requirements (use cases) into component-based requirements for the product line architecture. The result is a UML-based model-driven method that can be applied in combination with metamodeling tools such as the eclipse modeling framework (EMF) to derive the architecture of software product lines. We present our approach in a practical way and illustrate it with an example. We also discuss how our proposals are related to the work of other authors.     

基于J2EE的高校教务管理系统的分析与设计

目前基于intemet的应用软件复杂度越来越高,而且对软件的安全性、可依赖性及可扩展性的要求也越来越高。这使得软件的开发周期必然会加长。而SUN公司推出的J2EE架构使用多层的分布式模型,为企业级应用软件提供了良好的可伸缩性、灵活性和易维护性。以实例按照软件工程中软件开发的基本流程,详细介绍了此系统的需求分析、系统设计的过程。     

Behavioral profiles—a way to model and validate program behavior

Software architecture contains, in addition to its structural part, interaction patterns that can be regarded as part of the architectural solution of the system. The interaction patterns define architecturally significant behavior of the software system. In this paper we propose a visual modeling language, behavioral profiles, for specifying architecturally significant behavioral rules for an application. The language is built on the Unified Modeling Language (UML), which is a visual language widely used in software development. We show how behavioral profiles can be used to support software designers in creating behavioral models that conform to some predefined rules and for ensuring that an application behaves correctly with respect to the rules given in the profiles. A tool called Bebop was built to support software engineers in behavioral profile‐based design and analysis of program behavior. To evaluate the approach and the tools in different application domains, they are utilized in three cases. The size of the applications used in the cases varies from small to quite large software systems, and from academic to industrial ones. The examples demonstrate how the approach presented can be used in practice for different steps in a software engineering process. The examples cover specializing an application framework and monitoring the program execution in run‐time. In addition, they show how behavioral profiles can be used to support guided program comprehension and to validate program execution by analyzing execution traces. Copyright © 2010 John Wiley & Sons, Ltd.     

A software architecture for distributed computer control systems

Distributed computer control systems have a number of potential advantages over centralized systems, especially where the application is itself physically distributed. A computer station can be placed close to the plant being controlled, and a communications network used to enable the stations to communicate to coordinate their actions. However, the software must be carefully designed to exploit the potential advantages of distribution. This paper describes the software architecture of CONIC, a system to support distributed computer control applications. This architecture emphasizes the distinction between the writing of individual software components and the construction and configuration of a system from a set of components. A modular structure is used to separate programming from configuration. Typed entry and exit ports are used to clearly define module interfaces. Ports, analagous to the plugs and sockets of hardware components, permit modules to be interconnected in different ways. On-line modification and extension of the system is supported by permitting the dynamic creation and interconnection of modules. Message passing primitives are provided to permit modules to coordinate and synchronize control actions.     

A task graph execution manager for reconfigurable multi-tasking systems

Reconfigurable hardware can be used to build multi-tasking systems that dynamically adapt themselves to the requirements of the running applications. This is especially useful in embedded systems, since the available resources are very limited and the reconfigurable hardware can be reused for different applications. In these systems computations are frequently represented as task graphs that are executed taking into account their internal dependencies and the task schedule. The management of the task graph execution is critical for the system performance. In this regard, we have developed two different versions, a software module and a hardware architecture, of a generic task graph execution manager for reconfigurable multi-tasking systems. The second version reduces the run-time management overheads by almost two orders of magnitude. Hence it is especially suitable for systems with exigent timing constraints. Both versions include specific support to optimize the reconfiguration process.