服务化软件系统的运行时资源动态分配方法

Web软件是一种典型的基于Internet的软件形态,它自身的特点决定了其运行时的可靠保障以及质量优化都需要系统具有一定的自适应能力。对于服务化的Web软件系统而言,各服务之间的动态资源分配是实现运行时自适应的重要基础。针对这一问题,构建了一个基于Web的在线购物系统,并在此基础上对基于Web服务资源动态分配及负载均衡的Web软件系统运行时自适应技术进行了研究。对Web软件系统的运行时自适应管理问题进行了分析,提出并实现了资源动态分配及负载均衡方法,在此基础上针对在线购物系统进行了有效性验证。实验结果表明,优化的资源动态分配及负载均衡方法可以有效地提高Web软件系统的运行质量。     

基于适配的服务协作流程动态管理

服务协作以服务为构造单元,通过组合不同的服务,实现复杂的业务逻辑,并以此为基础构建新的应用.为实现正确的服务协作,服务之间的交互必须是兼容且一致的.适配技术通过构造适配器来弥补服务之间的交互差异,为解决协作的一致性问题提供了有效的方法途径.然而考虑到服务计算环境的动态特性,协作适配器本身应具有动态调整及重新配置的能力,从而避免使其成为协作系统响应动态变化的可适应能力的瓶颈.文中首先给出了一种基于适配的服务协作方法,以保证服务交互的一致性.并针对提出的适配器结构,建立了适配器的执行模型,在此基础上给出了适配器的动态更新方法,使适配器具有可重配置以及动态调整的能力,从而保证了基于适配的服务协作系统的灵活性和动态可适应性.     

Models@ run.time

Runtime adaptation mechanisms that leverage software models extend the applicability of model-driven engineering techniques to the runtime environment. Contemporary mission-critical software systems are often expected to safely adapt to changes in their execution environment. Given the critical roles these systems play, it is often inconvenient to take them offline to adapt their functionality. Consequently, these systems are required, when feasible, to adapt their behavior at runtime with little or no human intervention. A promising approach to managing complexity in runtime environments is to develop adaptation mechanisms that leverage software models, referred to as models@run. time. Work on models@run.time seeks to extend the applicability of models produced in model-driven engineering (MDE) approaches to the runtime environment. Models@run. time is a causally connected self-representation of the associated system that emphasizes the structure, behavior, or goals of the system from a problem space perspective.     

一种环境因素敏感的Web Service QoS监控方法

面向服务系统的执行能力依赖第三方提供的服务,在复杂多变的网络环境中,这种依赖会带来服务质量（QoS）的不确定性.而QoS是衡量第三方服务质量的重要标准,因此,有效监控QoS是对Web服务实现质量控制的必要过程.现有监控方法都未考虑环境因素的影响,比如服务器位置、用户使用服务的位置和使用时间段负载等,而这些影响在实际监控中是存在的,忽略环境因素会导致监控结果与实际结果有悖.针对这一问题,提出了一种基于加权朴素贝叶斯算法wBSRM（weightednaive Bayes running monitoring）的Web Service QoS监控方法.受机器学习分类方法的启发,通过TF-IDF（term frequency-inverse document frequency）算法计算环境因素的影响,通过对部分样本进行学习,构建加权朴素贝叶斯分类器.将监控结果分类,满足QoS标准为c₀,不满足QoS标准为c₁,监控时调用分类器得到c₀和c₁的后验概率之比,对比值进行分析,可得监控结果满足QoS属性标准、不满足QoS属性标准和不能判断这3种情况.在网络开源数据以及随机数据集上的实验结果表明：利用TF-IDF算法能够准确地估算环境因子权值,通过加权朴素贝叶斯分类器,能够更好地监控QoS,效率显著优于现有方法.     

Specification, decomposition and agent synthesis for situation-aware service-based systems

Service-based systems are distributed computing systems with the major advantage of enabling rapid composition of distributed applications, such as collaborative research and development, e-business, health care, military applications and homeland security, regardless of the programming languages and platforms used in developing and running various components of the applications. In dynamic service-oriented computing environment, situation awareness (SAW) is needed for system monitoring, adaptive service coordination and flexible security policy enforcement. To greatly reduce the development effort of SAW capability in service-based systems and effectively support runtime system adaptation, it is necessary to automate the development of reusable and autonomous software components, called SAW agents, for situation-aware service-based systems. In this paper, a logic-based approach to declaratively specifying SAW requirements, decomposing SAW specifications for efficient distributed situation analysis, and automated synthesis of SAW agents is presented. This approach is based on AS³ calculus and logic, and our declarative model for SAW. Evaluation results of our approach are also presented.     

基于模型的自适应方法综述

自适应为管理现代软件系统的复杂性提供了有效的解决方案,被设计为自适应系统的软件能够持续的演化以应对环境中的不确定性.在现有的研究工作中,基于模型的自适应方法是一类广泛使用的方法,它将模型驱动工程技术的应用从设计时扩展到运行时以支持自适应能力的实现.通过利用软件模型对运行时丰富和不确定的信息进行管理,这类方法避免了将自适应逻辑与程序语言交织带来的复杂性,从而简化了自适应系统的开发.本文对近些年来国内外学者在该研究领域取得的成果进行了系统总结.首先,给出了六个研究问题,包括相关工作常用的需求模型、结构模型、行为模型、环境模型、模型与模型或模型与系统间的同步方式、自适应规划算法等;接着,依次总结了相关工作在这六个研究问题上的已有研究成果;最后,对未来研究可能面临的挑战进行了展望.     

Portability of executable service-oriented processes: metrics and validation

A key promise of process languages based on open standards, such as the Web Services Business Process Execution Language, is the avoidance of vendor lock-in through the portability of processes among runtime environments. Despite the fact that today various runtimes claim to support this language, every runtime implements a different subset, thus hampering portability and locking in their users. It is our intention to improve this situation by enabling the measurement of the portability of executable service-oriented processes. This helps developers to assess their implementations and to decide if it is feasible to invest in the effort of porting a process to another runtime. In this paper, we define several software quality metrics that quantify the degree of portability of an executable, service-oriented process from different viewpoints. When integrated into a development environment, such metrics can help to improve the portability of the outcome. We validate the metrics theoretically with respect to measurement theory and construct validity using two validation frameworks. The validation is complemented with an empirical evaluation of the metrics using a large set of processes coming from several process libraries.     

Preference-driven personalization for flexible digital item adaptation

The delivery of multimedia content often needs the adaptation of the content in order to satisfy user constraints. With the Digital Item Adaptation part, the MPEG-21 standard already defines a useful frame-work to handle this task. However, in modern service-oriented architectures the functionality of adaptation is split over several services. Hence, the central instantiation of a suitable service chain needs to tackle a complex multi-objective optimization problem. In this problem between content choice and possible adaptations the current preference model in the MPEG-7/21 standard still lacks expressiveness. In the course of this paper we demonstrate this shortcoming and how the integration of more powerful models can ease the instantiation problem. Furthermore we explain how to efficiently evaluate preference trade-offs by evaluating skyline queries as currently investigated in the field of information systems. As a running example we use preference-based content adaptation in a typical media streaming application with Web services as basic modules. The contribution of our framework is to enable a central coordinator to instantiate an executable service composition chain by integrating all needed Web services to adapt the multimedia content in the best possible fashion in the sense of Pareto optimality. This work was supported in part by the German Research Foundation (DFG) within the Emmy-Noether Program of Exellence.     

An event-based approach for formally verifying runtime adaptive real-time systems

Real-time and embedded systems are required to adapt their behavior and structure to runtime unpredicted changes in order to maintain their feasibility and usefulness. These systems are generally more difficult to specify and verify owning to their execution complexity. Hence, ensuring the high-level design and the early verification of system adaptation at runtime is very crucial. However, existing runtime model-based approaches for adaptive real-time and embedded systems suffer from shortcoming linked to efficiently and correctly managing the adaptive system behavior, especially that a formal verification is not allowed by modeling languages such as UML and MARTE profile. Moreover, reasoning about the correctness and the precision of high-level models is a complex task without the appropriate tool support. In this work, we propose an MDE-based framework for the specification and the verification of runtime adaptive real-time and embedded systems. Our approach stands for Event-B method to formally verify resources behavior and real-time constraints. In fact, thanks to MDE M2T transformations, our proposal translates runtime models into Event-B specifications to ensure the correctness of runtime adaptive system properties, temporal constrains and nonfunctional properties using Rodin platform. A flood prediction system case study is adopted for the validation of our proposal.

     

Unifying design and runtime software adaptation using aspect models

Software systems are seen more and more as evolutive systems. At the design phase, software is constantly in adaptation by the building process itself, and at runtime, it can be adapted in response to changing conditions in the executing environment such as location or resources. Adaptation is generally difficult to specify because of its cross-cutting impact on software. This article introduces an approach to unify adaptation at design and at runtime based on Aspect Oriented Modeling. Our approach proposes a unified aspect metamodel and a platform that realizes two different weaving processes to achieve design and runtime adaptations. This approach is used in a Dynamic Software Product Line which derives products that can be configured at design time and adapted at runtime in order to dynamically fit new requirements or resource changes. Such products are implemented using the Service Component Architecture and Java. Finally, we illustrate the use of our approach based on an adaptive e-shopping scenario. The main advantages of this unification are: a clear separation of concerns, the self-contained aspect model that can be weaved during the design and execution, and the platform independence guaranteed by two different types of weaving.     

Program Control Language: a programming language for adaptive distributed applications

Many distributed applications must meet stringent performance requirements even when the performance characteristics of the underlying systems and networks vary significantly at runtime. Runtime adaptation can be used to tolerate such changes, but sophisticated adaptive distributed programs can be extremely challenging to design, implement and debug. This paper proposes a language called Program Control Language (PCL) that provides a novel means of specifying adaptations in distributed applications. PCL is based on an abstract, global representation of a distributed program (a static task graph), which enables a programmer to reason about and to describe a wide range of application-specific adaptation strategies at a high level, using a few key mechanisms. PCL provides simple high-level syntax for local and remote adaptation operations, local and remote performance monitoring (and aggregation), and for performing adaptations synchronously or asynchronously with respect to the execution of the application process initiating the adaptation. The global task graph representation enables remote performance metrics and adaptation operations to be specified in simple global terms by any process, and the compiler and runtime system automatically perform the communication and synchronization required for the remote operations. The paper describes the conceptual adaptation framework, the PCL language, and our implementation of the PCL compiler and runtime system. The paper uses three adaptative applications examples to illustrate the capabilities and benefits of PCL, and to show experimentally that the performance overheads of using PCL for implementing an adaptive application are negligible.     

Unifying design and runtime software adaptation using aspect models

Software systems are seen more and more as evolutive systems. At the design phase, software is constantly in adaptation by the building process itself, and at runtime, it can be adapted in response to changing conditions in the executing environment such as location or resources. Adaptation is generally difficult to specify because of its cross-cutting impact on software. This article introduces an approach to unify adaptation at design and at runtime based on Aspect Oriented Modeling. Our approach proposes a unified aspect metamodel and a platform that realizes two different weaving processes to achieve design and runtime adaptations. This approach is used in a Dynamic Software Product Line which derives products that can be configured at design time and adapted at runtime in order to dynamically fit new requirements or resource changes. Such products are implemented using the Service Component Architecture and Java. Finally, we illustrate the use of our approach based on an adaptive e-shopping scenario. The main advantages of this unification are: a clear separation of concerns, the self-contained aspect model that can be weaved during the design and execution, and the platform independence guaranteed by two different types of weaving.     

Evaluating Dynamic Task Mapping in Network Processor Runtime Systems

Modern network processor systems require the ability to adapt their processing capabilities at runtime to changes in network traffic. Traditionally, network processor applications have been optimized for a single static workload scenario, but recently several approaches for runtime adaptation have been proposed. Comparing these approaches and developing novel runtime support algorithms is difficult due to the multicore system-on-a-chip nature of network processors. In this paper, we present a model for network processors that can aid in evaluating different runtime support systems. The model considers workload characteristics of applications and network traffic using a queuing network abstraction. The accuracy of this analytical approach to modeling runtime systems is validated through simulation. We illustrate the effectiveness of our model by comparing the performance of two existing workload adaptation algorithms.     

Experiments Toward a Mutual Adaptive Speech Interface That Adopts the Cognitive Features Humans Use for Communication and Induces and Exploits Users' Adaptations

Interactive agents such as pet robots or adaptive speech interface systems that require forming a mutual adaptation process with users should have two competences. One of these is recognizing reward information from users' expressed paralanguage information, and the other is informing the learning system about the users by means of that reward information. The purpose of this study was to clarify the specific contents of reward information and the actual mechanism of a learning system by observing how 2 persons could create a smooth speech communication, such as that between owners and their pets.

A communication experiment was conducted to observe how human participants create smooth communication through acquiring meaning from utterances in languages they did not understand. Then, based on experimental results, a meaning-acquisition model that considers the following 2 assumptions was constructed: (a) To achieve a mutual adaptive relationship with users, the model needs to induce users' adaptation and to exploit this induced adaptation to recognize the meanings of a user's speech sounds; and (b) to recognize users' utterances through trial-and-error interaction regardless of the language used, the model should focus on prosodic information in speech sounds, rather than on the phoneme information on which most past interface studies have focused.

The results confirmed that the proposed model could recognize the meanings of users' verbal commands by using participants' adaptations to the model for its meaning-acquisition process. However, this phenomenon was observed only when an experimenter gave the participants appropriate instructions equivalent to catchphrases that helped users learn how to use and interact intuitively with the model. Thus, this suggested the need for a subsequent study to discover how to induce the participants' adaptations or natural behaviors without giving these kinds of instructions.     

C／S遗留系统到SOA系统移植框架研究

遗留系统在组织中起着重要的作用。随着商业环境的快速变化，应该不断用新技术对其进行进化。Web Service和面向服务的体系结构（SOA）使我们能在面向服务的计算环境中进化遗留系统。用web Service技术集成遗留系统的传统方法是将遗留系统包装成“黑盒子”。本文提出了一种再工程方法，该方法将遗留系统的包装和理解相结合。该方法不仅能对服务进行识别和包装，还可以将遗留系统移植到SOA的体系结构中。     

Towards the Model Driven Development of context-aware pervasive systems

In this work, we introduce a Model Driven Development method for developing context-aware pervasive systems. This method allows us to specify a context-aware pervasive system at a high level of abstraction by means of a set of models, which describes both the system functionality and the context information. From these models, an automated code generation strategy is applied. This strategy allows us to generate the system Java code that provides the system functionality and as well as an OWL specification that represents the context information and allows us to manage this information without additional burden. Furthermore, this specification is used by a reasoner at runtime to infer context knowledge that is not directly observable, and it is also used by machine learning algorithms to give support to the system adaptation according to the context information.     

一种Android平台混合应用运行环境

随着智能终端设备以及移动互联网的发展,智能手机等设备越来越普遍,其上的应用也越来越丰富. 如何能够更快、更高效的开发智能终端上的应用成为开发者面临的巨大问题之一. 在分析了当前存在的跨平台混合应用开发的基础上,设计并实现了一种Android平台混合应用运行环境,利用该运行环境可以实现只用HTML、CSS和JavaScript开发Android应用,为开发者带来极大的便利. 同时该运行环境兼容桌面系统上的混合应用运行环境,利用该运行环境开发的应用经过不同屏幕适配同时可以运行在桌面系统上.     

Rapid Prototyping of Adaptable User Interfaces

User interface adaptation has been proposed in recent years as a means to achieve personalized accessibility and usability of user interfaces. Related user interface architectures, as well as a variety of related development method and tools, have also been elaborated. Admittedly, however, despite the recognized validity of the approach, which has been proved in practice in a series of prototype systems, the wider adoption and uptake of user interface adaptation approaches are still limited. One of the identified obstacles is the complexity intrinsic in designing such interfaces and the need of radically revising the current user interface design practice to account for (a) the alternative designs required for adaptation, (b) the parameters involved in driving adaptations (i.e., selecting among alternatives at a given point during interaction), and (c) the logic of adaptation at runtime. This article proposes a twofold tool-based support strategy for user interface adaptation development, based on (a) an adaptation development toolkit and related widget library, which directly embeds lexical level adaptations into common interactive widgets, and (b) embedding such a library in a common integrated development environment, thus allowing designers to define and view alternative adaptations at design time and create adaptable user interfaces through traditional prototyping. The aforementioned approach has been implemented in the domain of adaptable applications for older users, producing tools that are currently in use in the development of a large suite of interactive applications in various domains. The approach presented in this article is claimed to be the first and so far unique supporting rapid prototyping of adaptable user interfaces, thus minimizing the divergence between typical development practices and user interface adaptation development.     

A resource-aware framework for resource-constrained service-oriented systems

As embedded systems become increasingly complex, not only are dependability and timeliness critical quality indicators, but also their ability to dynamically adapt to changes in their runtime environment. Service-oriented Architecture (SOA) offers a potential solution to this challenge by allowing services to be dynamically bound at runtime. However, resource contention between services and resource saturation can result in significant Quality of Service (QoS) degradation. To address these issues, this paper proposes a runtime, resource-aware architecture that combines resource monitoring with dynamic workflow orchestration to mediate resource contention within the orchestration environment. The architecture was evaluated on a medium-size service-oriented case study, deployed on a resource-constrained device.