云计算环境中SaaS的接入控制和调度策略研究

SaaS是一种基于网络的软件应用模式,是服务提供商将应用软件统一部署在自己的服务器上,用户根据自己的实际需要,通过互联网向服务提供商订购并支付自己所需的服务。在未来,SaaS模式是占主导地位的云服务模型。文中阐述SaaS的基本概念,介绍了SaaS的参考结构以及服务流程,分析概括了不同类型的服务要求的接人控制策略,总结了不同性能要求作业的调度策略,最后结合已有的云计算环境下的SaaS接入控制和调度策略研究成果,展望了未来的研究方向和亟待解决的关键问题。     

Model checking response times in Networked Automation Systems using jitter bounds

Response time (RT) of Networked Automation Systems (NAS) is affected by timing imperfections induced due to the network, computing and hardware components. Guaranteeing RT in the presence of such timing imperfections is essential for building dependable NAS, and to avoid costly upgrades after deployment in industries.This investigation proposes a methodology and work-flow that combines modelling, simulation, verification, experiments, and software tools to verify the RT of the NAS during the design, rather than after deployment. The RT evaluation work-flow has three phases: model building, modelling and verification. During the model building phase component reaction times are specified and their timing performance is measured by combining experiments with simulation. During the modelling phase, component based mathematical models that capture the network architecture and inter-connection are proposed. Composition of the component models gives the NAS model required for studying the RT performance on system level. Finally, in the verification step, the NAS formal models are abstracted as UPPAAL timed automata with their timing interfaces. To model timing interfaces, the action patterns, and their timing wrapper are proposed. The formal model of high level of abstraction is used to verify the total response time of the NAS where the reactions to be verified are specified using a subset of timed computation tree logic (TCTL) in UPPAAL model checker. The proposed approach is illustrated on an industrial steam boiler deployment.     

基于SaaS的弹性云平台优化调度策略设计

云计算平台利用虚拟化技术使软件应用变得更有效率的同时, 也给资源管理和服务调度带来了挑战。在研究了软件服务（SaaS）与基础设施服务（IaaS）调度的区别基础上, 重点考虑SaaS层的资源调度, 提出基于随机理论的调度模型, 把该层调度描述成一种多目标的优化问题。除了服务质量的要求, 还考虑了弹性这一云服务的重要特性, 并提供了任务调度与弹性服务副本的匹配策略。实验表明本调度机制的设计优化了云平台的整体性能, 达到了较好的负载均衡与资源利用率。     

基于云计算的网站群架构及安全性设计与实践

该文以政府机构网站群建设为对象,搭建了网站群云计算构建的实验与应用平台,阐述了应用云计算支撑政府机构网站群架构及其安全性设计和应用方法i,该文主要从两方面满足网站群应用需求,一方面,以IaaS（Infrastructure as a Service）的模式搭建支撑网站群应用的云计算基础平台,以SaaS（Software as a Service）的模式搭建网站群内容管理云计算平台,另一方面,通过构建公共云和私有云环境,保障网站群系统安全和信息安全。以云计算为平台,向用户提供一站式的网站群建设、运行、监控服务,将成为政府网站群建设的新的方向．     

一种面向SaaS多租户的多层模型

SaaS(Software as a Service)伴随云计算而出现,它与传统软件的区别较大。根据SaaS软件的特点,提出支持SaaS软件成熟度的SaaS软件分层元模型,使用形式化方法对每一层进行建模描述。受面向对象Petri网(Object-Oriented Petri Nets,OOPN)和有色Petri网(Colored Petri Nets,CPN)思想的启发,提出面向服务网结构SOP(Service-Oriented Petri Nets)和CSOP(Colored Service-Oriented Petri Nets)。一方面,使用封装的库所元素代表服务,体现了服务对外不可见,且内部结构影响系统运行。另一方面,不同的颜色集代表不同租户请求,突出了SaaS多租户的特点。这不仅为复杂的SaaS软件建模提供了方法,还能够折叠系统变迁,压缩状态空间。最后,以一个 客户关系管理 (Customer Relationship Management,CRM)SaaS软件系统为例,验证了文中工作的可行性。     

支持多类终端与服务定制的SaaS软件服务架构

由软件即服务(SaaS)模式中软件服务的概念与特点分析,可知现有的面向服务架构(SOA)不能完全支持软件服务的实现。此外,为了拓展软件服务的应用范围,实现多样化的服务,SaaS模式的软件服务必然要满足用户定制服务的需求,以及对多类用户终端的支持。通过对SOA的扩展,在其中引入了软件服务终端、软件服务端口、软件服务注册等模块,提出了一种支持多类终端与服务定制的SaaS软件服务架构,给出了该架构的结构与工作流程,并通过实验证明了该架构可以实现SaaS模式的软件服务,而且能够实现对上述功能需求的支持。     

面向SaaS应用的SMTDM可伸缩多租户数据管理框架

云计算是一种可以弹性并按需提供资源的技术.在多租户共享数据存储模式下,如何实现数据的动态伸缩存储是云数据管理的关键.针对SaaS应用如何随着租户数量及请求规模的变化而进行自适应伸缩的问题,在分析数据存储层的伸缩性需求的基础上,基于Walraven等人提出的多租户架构思想,扩展典型的云应用架构,设计了一个多租户数据管理框架,实现存储资源的弹性.基于该框架,开发了一个面向网络管理领域的SaaS原型系统,验证了其有效性和可用性.     

基于可变性模型的可复用与可定制SaaS软件开发方法

云计算环境下,软件通过互联网向租户提供服务,这种基于互联网的软件交付模式称为SaaS（软件即服务）.与传统软件交付模式相比,SaaS软件通常运行于软件供应商的服务器端,同时为多个租户提供服务.由于需要支持不同租户的个性化需求,SaaS软件应具备足够的灵活性,以应对快速变化的租户需求;而且针对某一个租户的变更,不应影响其他租户.通过扩展课题组前期开发的基于可变性管理的适应性服务组装方法及其支持平台,提出了一种云计算环境下可复用、可定制的SaaS软件开发方法,开发了相应的支持平台,包括支持SaaS模式的服务组装引擎和远程定制工具.该方法针对不同租户的共性需求,提供一个抽象服务组装模型,支持平台在运行阶段解释执行抽象服务组装模型,根据租户的个性化需求派生不同的流程实例,这些运行时流程实例多态共存、互不影响.采用一个特定领域的SaaS软件实例来验证该方法的可行性,评估了支持平台的性能.实验结果表明,该方法及其支持平台可以支持多实例多租户的交付模式.     

基于SaaS模式的信息系统架构优化研究与应用

SaaS模式作为云计算模式之一,有着多租户且可配置的特点。SaaS模式较好地解决了软件架构在扩展能力与资源共享等方面存在的问题。在研究中以SaaS信息系统架构在数据存储层与访问控制层方面所进行的分析为基础,确定了多稀疏表和键值对结合的模型,探讨了该模型所具有的优势。该研究对优化我国信息系统架构有一定的参考作用。     

Software-as-a-service （SaaS）： perspectives and challenges

Software-as-a-service （SaaS） has received significant attention recently as one of three principal components of cloud computing, and it often deals with applications that run on top of a platform-as-a-service （PaaS） that in turn runs on top of infrastructure-as-a-service （IaaS）. This paper provides an overview of SaaS including its architecture and major technical issues such as customization, multi-tenancy architecture, redun- dancy and recovery mechanisms, and scalability. Specifically, a SaaS system can have architecture relating to a database-oriented approach, middleware-oriented approach, service-oriented approach, or PaaS-oriented ap- proach. Various SaaS customization strategies can be used from light customization with manual coding to heavy customization where the SaaS system and its underlying PaaS systems are customized together. Multi-tenancy architecture is an important feature of a SaaS and various trade-offs including security isolation, performance, and engineering effort need to be considered. It is important for a SaaS system to have multi-level redundancy and recovery mechanisms, and the SaaS system needs to coordinate these with the underlying PaaS system. Finally, SaaS scalability mechanisms include a multi-level architecture with load balancers, automated data migration, and software design strategies.     

基于SaaS模式的电子政务架构研究

SaaS模式作为云计算的一种形式,在互联网技术的发展和应用软件成熟的基础上,成为一种创新的软件应用模式。如何保证系统安全与设计高效安全的数据架构是决定SaaS应用成败的关键问题。本文将以基于SaaS的政务系统为业务依托,以数据库设计和系统安全、SoA为理论基础,提出STEG解决方案。此解决方案在SaaS软件中能很好的解决数据建模、系统安全和软件架构方面的问题,对SaaS下的软件研究具有深刻借鉴意义。     

元数据驱动的BI-PAAS的设计与实现

针对传统的商业智能软件功能单一、计算性能低、无法满足用户快速搭建应用和处理海量数据的需求,提出了一个新的基于云计算的商业智能平台（BI-PAAS）方案。在对该平台需求分析的基础上,给出了平台的体系架构设计,重点讨论了分层式元数据描述规范,并通过一个应用实例验证了该平台提供海量数据处理和快速开发丰富的BI应用的可行性,阐述了该平台的应用前景。     

Verification of a Radio-Based Signaling System Using the STATEMATE Verification Environment

With the trend to partially move safety-related features from courtyards into on-board control software, new challenges arise in supporting such designs by formal verification capabilities, essentially entailing the need for a model-based design process. This paper reports on the usage of the STATEMATE Verification Environment to model and verify a radio-based signaling system, a trial case study offered by the German train system company DB. It shows, that industrially sized applications can be modeled and verified with a verification tool to be offered as a commercial product by I-Logix, Inc.     

面向云网融合SaaS安全的虚拟网络功能映射方法

在云网融合背景下,承载软件即服务（SaaS）业务功能的云基础设施可能横跨多个数据中心和归属网络,难以保证云资源安全可控。为缩短SaaS业务服务的处理时延,设计基于冗余执行和交叉检验的SaaS组合服务模式,并对容器、Hypervisor和云基础设施的安全威胁进行建模,建立拟态化虚拟网络功能映射模型和安全性优化机制。在此基础上,提出基于近端策略优化的PJM算法。实验结果表明,与CCMF、JEGA和QVNE算法相比,PJM算法在满足安全性约束的条件下,能够降低约12.2%业务端到端时延。     

Rafhyc: an Architecture for Constructing Resilient Services on Federated Hybrid Clouds

Federated hybrid clouds is a model of service access and delivery to community cloud infrastructures. This model opens an opportunity window to allow the integration of the enhanced science (eScience) with the Cloud paradigm. The eScience is computationally intensive science that is carried out in highly distributed computing infrastructures. Nowadays, the eScience big issue on Cloud Computing is how to leverage on-demand computing in scientific research. This requires innovation at multiple levels, from architectural design to software platforms. This paper characterizes the requirements of a federated hybrid cloud model of Infrastructure as a Service (IaaS) to provide eScience. Additionally, an architecture is defined for constructing Platform as a Service (PaaS) and Software as a Service (SaaS) in a resilient manner over federated resources. This architecture is named Rafhyc (for Resilient Architecture of Federated HYbrid Clouds). This paper also describes a prototype implementation of the Rafhyc architecture, which integrates an interoperable community middleware, named DIRAC, with federated hybrid clouds. In this way DIRAC is providing SaaS for scientific computing purposes, demonstrating that Rafhyc architecture can bring together eScience and federated hybrid clouds.     

A semantic interoperability framework for software as a service systems in cloud computing environments

In cloud computing environments in software as a service (SaaS) level, interoperability refers to the ability of SaaS systems on one cloud provider to communicate with SaaS systems on another cloud provider. One of the most important barriers to the adoption of SaaS systems in cloud computing environments is interoperability. A common tactic for enabling interoperability is the use of an interoperability framework or model. During the past few years, in cloud SaaS level, various interoperability frameworks and models have been developed to provide interoperability between systems. The syntactic interoperability of SaaS systems have already been intensively researched. However, not enough consideration has been given to semantic interoperability issues. Achieving semantic interoperability is a challenge within the world of SaaS in cloud computing environments. Therefore, a semantic interoperability framework for SaaS systems in cloud computing environments is needed. We develop a semantic interoperability framework for cloud SaaS systems. The capabilities and value of service oriented architecture for semantic interoperability within cloud SaaS systems have been studied and demonstrated. This paper is accomplished through a number of steps (research methodology). It begins with a study on related works in the literature. Then, problem statement and research objectives are explained. In the next step, semantic interoperability requirements for SaaS systems in cloud computing environments that are needed to support are analyzed. The details of the proposed semantic interoperability framework for SaaS systems in cloud computing environments are presented. It includes the design of the proposed semantic interoperability framework. Finally, the evaluation methods of the semantic interoperability framework are elaborated. In order to evaluate the effectiveness of the proposed semantic interoperability framework for SaaS systems in cloud computing environments, extensive experimentation and statistical analysis have been performed. The experiments and statistical analysis specify that the proposed semantic interoperability framework for cloud SaaS systems is able to establish semantic interoperability between cloud SaaS systems in a more efficient way. It is concluded that using the proposed framework, there is a significant improvement in the effectiveness of semantic interoperability of SaaS systems in cloud computing environments.     

基于概率模型检验的云渲染任务调度定量验证

云渲染技术已被广泛应用于影视和动漫等行业.与传统的渲染农场和租赁市场模式不同，云渲染系统依托云计算基础设施提供多种软件服务进行渲染作业的方式，正逐渐成为新兴的计算模式.由于任务执行和资源操作等作业调度对于用户而言是透明的，这要求云渲染系统应具备智能化以实现计算资源优化调度和多端任务管理，并对系统可靠性提出了更高要求.针对这一问题，提出了采用概率模型检验对云渲染系统任务调度进行定量评估.首先，考虑渲染服务失效等因素引发的随机系统异常和指令错误，如文件损坏和渲染任务超时等，提出了基于离散马尔可夫链（DTMC）的概率模型对云渲染系统的文件准备模块、资源请求模块、渲染任务执行模块进行形式化建模；其次，从服务质量属性角度提出了9类验证性质用于定义云渲染系统的可靠性，采用概率计算树逻辑（PCTL）描述检验性质公式并执行工具PRISM计算和验证渲染系统可靠性；最后，结合案例和实验证明了该方法的可行性和有效性，尤其是对改进前后云渲染系统进行定量检验，可用于指导如何进行失效恢复和任务切换.因此，该方法在一定程度上可提高云渲染系统的可靠性.     

基于云计算的工商办公自动化系统的设计与实现

办公自动化系统是为适应现代无纸化及网络化办公的趋势,更好地服务于现代办公操作,基于B/S模式而开发的一套应用于工商系统的办公自动化系统.系统在设计与实现上基于云服务模式,将系统构架分为基础设施层(IaaS)、系统平台层(PaaS)、应用服务层(SaaS).基于云服务平台的设计,能够提升系统的可靠性和数据存储安全性,实现硬件资源共享和动态调整,实现应用弹性部署,为各机关提供个性化定制服务,降低运维成本、实现节能减排,并提升技术的先进性,并奠定业务的可扩展基础.