A service accountability framework for QoS service management and engineering

Service science, management and engineering (SSME) research is to study the methodology and technology for service innovation, design, development and delivery. Since service industry is very quality-sensitive and trust-dependent, we propose a service accountability management framework to detect, diagnose, defuse and disclose the root cause for any problematic service process. The accountability support is important for SSME since service processes often rely on external service providers to deliver part of the service functionalities. A service system must have effective yet efficient mechanisms to ensure that every external service is delivering a consistent and acceptable level of performance to meet the end-to-end quality of service (QoS) of the whole service process. In this paper, we present the accountability framework, identify the components in an accountable service architecture, and design an accountability diagnosis methodology. We also briefly present the inteLLigent Accountability Management Architecture (LLAMA) project which implements the accountability service bus (ASB), an agent-based middleware to support the monitoring, diagnosis, and reconfiguration of e-services. LLAMA ASB interacts with accountability agents to monitor services and the Accountability Authority to automatically diagnose faulty situations. The LLAMA technology is useful to ensure the QoS in SSME-based systems.     

基于监视的服务质量评估方法

在面向服务的体系结构(Service Oriented Architecture,SOA)中,消费者的目标是发现和使用高质量的服务。随着Web服务数量的不断增加,为用户推荐和选择最满足需求的Web服务已经成为服务计算领域最重要的挑战之一。在SOA中,传统的质量评估方法偏重于消费者获得更高的性能,未充分考虑消费者的个性化需求,这样,并不一定让消费者获得完全满足其需求的服务。因此,在服务选择和推荐过程中不仅需要考虑服务的功能性需求,还需要考虑服务的非功能性需求。而且,服务质量的改变只能在服务运行过程中才能被发现。为了解决上述问题,本文提出一种基于监视的服务质量评估方法,充分考虑服务的功能性和非功能性属性,建立统一模型,根据监视数据动态评估服务质量,为动态环境下选择和推荐服务提供依据。本文最后描述了该方法的实现框架。     

An adaptive algorithm for QoS-aware service composition in grid environments

Service composition enables users to realize their complex needs as a single request and it has been recognized as a flexible way for resource sharing and application integration since the appearance of Service-Oriented Architecture (SOA). For each of the needed individual services there may be many candidate services available presented by different vendors and with different functional and non-functional properties such as Quality of Service (QoS). Approaches are needed to select candidate services with various QoS levels according to user’s performance requirements meanwhile adapt to dynamic churn in grid environments. This paper mainly focuses on adaptive management of QoS-aware service composition in grid environments and proposes an adaptive algorithm for QoS-aware service composition (AQSC). In AQSC we model this problem as the Multi-Constrained Optimal Path selection problem (MCOP) and use heuristic approach for service selection, then backup services set is introduced as an adaptive mechanism so as to ensure the fulfillment of composite service when some candidate services fail or withdraw. Both theoretical analysis and simulation results indicate that AQSC has high composition success rate, finish rate and low cost.     

一种利用云环境实现Web服务组合容错的方法

随着Web服务迅猛发展,基于SOA的服务组合容错性研究成为了业界关注的焦点.服务组合中组件的失效,会导致整个组合执行失败,而资源不足、服务器负载过重是引发组件失效的主要原因之一.云计算作为一种新的计算泛型,其资源整合、动态分配的特点为解决传统SOA下因资源受限而引发的失效提供了新的容错思路.FTEL层将中间件技术应用到服务组合容错上,借助云环境完成服务替换,对传统SOA下较难解决的由于资源问题引起的组件失效进行了容错.     

QoS Requirement Generation and Algorithm Selection for Composite Service Based on Reference Vector

Under SOA (Service-Oriented Architecture), composite service is formed by aggregating multiple component services together in a given workflow. One key criterion of this research topic is QoS composition. Most work on service composition mainly focuses on the algorithms about how to compose services according to assumed QoS, without considering where the required QoS comes from and the selection of user preferred composition algorithm among those with different computational cost and di?erent selection resu...     

SRM: a staged reliability model for Web service

SOA (Service-oriented Architecture) is becoming the major architecture for building complex Web service systems. In SOA, the lifecycle of Web services consists of four stages: service publication, service discovery, service binding and service execution. Faults may occur in any stage and cause a failure of service. The reliability of services depends on not only the faults of the remote services itself, but also the faults that may occur in any SOA stage. Designing an effective and accurate reliability prediction model for Web services has become an important and necessary task. This study first proposes a staged reliability model for atomic services, which structures the reliability estimation based on the faults that may occur at each stage. Then, the reliability of composite services or service systems can be estimated based on this staged model. An experiment is conducted to study the influence of failures at each stage on the reliability of atomic services and a case study is designed to demonstrate the reliability of composite services using our staged model. In addition, the accuracy of our approach is investigated by comparing it against CBRM (component-based reliability model). Sensitivity analysis is also performed to identify critical service. Experimental results show that our staged model can obtain higher reliability prediction accuracy and is more suitable for Web services than traditional model.     

基于P2P的Web服务发现机制研究

在P2P系统中融入Web服务的相关技术,将传统的P2P系统转变为一种面向服务的架构是分布式计算发展的方向,而Web服务的自动发现是面向服务的架构要解决的关键问题之一.提出了一种基于P2P技术和语义Web的服务发现机制,将P2P系统作为服务的提供者整体接入Web服务,通过P2P网络实现服务描述信息的自动交换,并采用分段搜索机制处理用户查询,从而提高了用户查询的效率和准确性.     

从面向对象的遗留系统到面向服务架构的迁移方法

Migrating legacy system with web service is an effective and economic way of reusing legacy software in a SOA environment. In this paper, we present an approach for migrating a three-tie object-oriented legacy system to SOA environment. The key issue of the approach is about services identification from large numbers of classes. And we propose a bottom-up method to model the system with UML and identify services from UML then. This approach can be a reference to an auto-migrating process.     

Web服务调整策略研究

随着SOA技术的快速发展,由于分布式Web服务的不稳定性导致的服务组合失效问题逐渐成为Web服务领域的一个重要研究内容。为解决部分Web服务失效造成的组合服务失效问题,文中简要介绍了Web服务及其QoS属性指标,研究了几种常见的Web服务自适应调整方法,分析比较了典型的Web服务调整策略的优缺点。研究表明,建立服务备份集的方法能够有效地提高服务故障修复效率,同时在服务选择阶段引入评估优化机制能够大大降低服务失效率,因此,将两种方法进行有效结合将很好地提高组合服务的稳定性。     

基于Web Services的企业间SOA模型研究

针对当前企业应用集成存在的诸多问题,提出了一种基于网络服务的面向服务架构企业应用集成模型.该模型通过在企业已存在的系统之上建立基于原子服务的合成服务封装层和业务流程层,按照迭代方法来定义企业间服务,从而为企业问信息共享与应用集成提供了一种有效方法与全新机制.在某企业应用集成实践中表明,该模型具有较好的可重用性与开放性.     

A taxonomic framework for autonomous service management in Service-Oriented Architecture

Since Service-Oriented Architecture （SOA） reveals the black box nature of services, heterogeneity, service dynamism, and service evolvability, managing services is known to be a challenging problem. Autonomic computing （AC） is a way of designing systems that can manage themselves without direct human intervention. Hence, applying the key disciplines of AC to service management is appealing. A key task of service management is to identify probable causes for symptoms detected and to devise actuation methods that can remedy the causes. In SOA, there are a number of target elements for service remedies, and there can be a number of causes associated with each target element. However, there is not yet a comprehensive taxonomy of causes that is widely accepted. The lack of cause taxonomy results in the limited possibility of remedying the problems in an autonomic way. In this paper, we first present a meta-model, extract all target elements for service fault management, and present a computing model for autonomously managing service faults. Then we define fault taxonomy for each target element and inter-relationships among the elements. Finally, we show prototype implementation using cause taxonomy and conduct experi- ments with the prototype for validating its applicability and effectiveness.     

The design and implementation of service process reconfiguration with end-to-end QoS constraints in SOA

Service processes in SOA are composed dynamically by services from different service providers. At run-time, some services may become faulty and cause a service process to violate its end-to-end quality of service (QoS) constraints. We propose an effective approach for replacing only faulty services and some of their neighboring services to maintain the original end-to-end QoS constraints. We use an iterative algorithm to search for a reconfiguration region that has replaceable services to meet the original QoS constraint for the region. Services in reconfiguration regions may be replaced using one-to-one, one-to-many, or many-to-one service mappings. By replacing only services in reconfiguration regions rather than the whole service process, reconfiguration overheads are lowered and service disruptions may be reduced. We have implemented the Adaptation Manager in the Llama ESB middleware. Performance study shows that our approach may efficiently repair service processes.     

A taxonomic framework for autonomous service management in Service-Oriented Architecture

Since Service-Oriented Architecture (SOA) reveals the black box nature of services,heterogeneity,service dynamism,and service evolvability,managing services is known to be a challenging problem.Autonomic computing (AC) is a way of designing systems that can manage themselves without direct human intervention.Hence,applying the key disciplines of AC to service management is appealing.A key task of service management is to identify probable causes for symptoms detected and to devise actuation methods that can remedy the causes.In SOA,there are a number of target elements for service remedies,and there can be a number of causes associated with each target element.However,there is not yet a comprehensive taxonomy of causes that is widely accepted.The lack of cause taxonomy results in the limited possibility of remedying the problems in an autonomic way.In this paper,we first present a meta-model,extract all target elements for service fault management,and present a computing model for autonomously managing service faults.Then we define fault taxonomy for each target element and inter-relationships among the elements.Finally,we show prototype implementation using cause taxonomy and conduct experiments with the prototype for validating its applicability and effectiveness.     

Business processes oriented heterogeneous systems integration platform for networked enterprises

Supply chains, dynamic alliances, e-business, extended enterprises, and virtual organizations are typical networked enterprises which are formed based on partner companies’ core competencies. Different partners have different infrastructures; the interoperability among heterogeneous systems is the solid foundation for the networked enterprise to work seamlessly and effectively. Due to the distributed and heterogeneous characteristics of different partner companies, it is a big challenge to implement a satisfying and cost effective solution in the networked enterprise.Aiming at the problems of system integration and cross-system interoperability, Service-Oriented Architecture (SOA) provides a new integration pattern and relative system infrastructure. The key for the development and implementation of SOA is services encapsulation and orchestration of applications through certain mechanism to operate a complex business. However, cross infrastructures services access protection and relative services orchestration are still the bottleneck for the SOA implementation.This paper develops a business processes oriented heterogeneous systems integration platform with relative methodology for networked enterprises integration. The platform is a space distributed and management centralized platform for networked enterprises. The service access agent (SAA) mechanism is developed to realize cross-domains identity authentication, service authorization, and information transmission security. Every Web service or SAA in the platform has a unique ID. The interoperating process only relies on IDs, which endows the platform with a loose coupling feature. Aiming at service orchestration, a graphic service process modelling method is developed, with which the developed process model can link atom Web services and form a complex service. The Java based service orchestration tool provides an ESB (Enterprise Service Bus) independent service orchestration and deployment. Those services that are results of orchestration can be orchestrated as an atom service in another orchestrating process. Thus, the platform can support orchestration decomposition. The structure approach of the business process modelling based platform implementation is developed, which provides a guideline for platform installation, services modelling, service encapsulation, service orchestration, and service deployment. Two cases are provided to illustrate the usage of the platform in industries. The development of this platform is an open source project.     

基于本体的数字家庭SOA服务发现机制

SOA的关键是服务,它为WebService提供了一个架构,使用该架构组织家庭服务可以实现跨平台的服务访问。然而SOA架构大多数规范如SOAP、UDDI和WSDL等均是基于XML的,所描述的服务缺乏语义信息,因此在检索过程无法有效处理一词多义和多词一义等语法问题。通过引入本体技术,建立家庭服务领域本体,从服务的功能、内容和设备三个方面利用功能概念本体、内容本体和设备本体进行语义标注,并扩展WSDL为S-WSDL来描述家庭服务。基于本体的家庭服务发现过程分为三个阶段:查找功能、过滤服务和参数类型匹配,充分利用本体的语义优势实现了智能数字家庭服务发现。     

Building Accountability Middleware to Support Dependable SOA

The Intelligent Accountability Middleware Architecture (Llama) project supports dependable service-oriented architecture (SOA) monitoring, runtime diagnosis, and reconfiguration. At its core, Llama implements an accountability service bus that users can install on existing service-deployment infrastructures. It collects and monitors service execution data from a key subset of services; enables Llama users to incorporate others' advanced diagnosis models and algorithms into the framework; and provides enterprise service bus extensions for collecting service profiling data, thus making process problems transparent to diagnose. Finally, experimental results indicate that using Llama contributes a modest amount of system overhead.     

Adaptive Service Composition in Flexible Processes

In advanced service oriented systems, complex applications, described as abstract business processes, can be executed by invoking a number of available Web services. End users can specify different preferences and constraints and service selection can be performed dynamically identifying the best set of services available at runtime. In this paper, we introduce a new modeling approach to the Web service selection problem that is particularly effective for large processes and when QoS constraints are severe. In the model, the Web service selection problem is formalized as a mixed integer linear programming problem, loops peeling is adopted in the optimization, and constraints posed by stateful Web services are considered. Moreover, negotiation techniques are exploited to identify a feasible solution of the problem, if one does not exist. Experimental results compare our method with other solutions proposed in the literature and demonstrate the effectiveness of our approach toward the identification of an optimal solution to the QoS constrained Web service selection problem     

A multi-agent-based framework for cloud service discovery and selection using ontology

As cloud computing is getting matured day by day, there has been overwhelming interest among the users to avail a plethora of cloud services. Often, these services appear identical in terms of their functionality though they differ in pricing models, computational power, storage policies and Quality-of-Service parameters making the process of service discovery and selection an intricate task. In the absence of any standard specifications, cloud service providers continue to use their own vocabulary and this further complicates the selection process. Even popular search engines like Google and MSN are not efficient enough to properly identify the most appropriate cloud service that can meet customer requirements. Thus, in the presence of multiple selection parameters and constraints, selecting a required cloud service is a daunting task. In order to address this issue, we work toward developing a reasoning mechanism to optimally resolve the similarities across cloud services by using cloud ontology. A multi-agent-based framework has been proposed for effective cloud service discovery and selection with the help of a standardized service registry and by employing semantically guided searching process.