基于原生数据库的SaaS存储模型

SaaS应用中的多租户数据存储是当前的热门研究点, 现有解决方案大都基于关系数据库, 采用模式映射技术. 从SaaS的存储灵活性和分布式特点分析了使用原生XML数据库的可行性, 并给出了适合多租户数据的XML存储结构, 能够有效支持SaaS的上述特点.     

可信的自治式服务协同多租户租赁模型

规范调控、策略驱动的自治式服务协同模型NGPD,可以解决因自治个体行为难以预测、控制而导致的协同效应“可信”危机。然而,服务协同的广泛部署需要众多中小企业的参与,但协同模型NGPD部署、升级管理的复杂性难以为中小企业胜任,势必成为NGPD发展和商业应用的瓶颈。结合云计算中“软件即服务”（Soft as a Service,SaaS）的概念,采用托管集成、集中部署、租户定制等方式来解决该问题,有助于增加NGPD的实用价值和商业价值。     

面向SaaS应用的业务逻辑定制框架的研究与实现*

SaaS（software as a service,软件即服务）是一种全球兴起的创新的软件服务模式,它的出现对中小企业的信息化产生了深远影响。目前面向SaaS应用的业务逻辑在线定制方法存在着定制复杂性高、可定制内容有限等缺点。为了解决这些问题,采用了基于领域工程的业务规则模板的方法,提出了适合SaaS应用的业务逻辑定制框架,兼顾了应用的易用性及性能。案例表明了此框架的有效性。     

Metrics and techniques for quantifying performance isolation in cloud environments

The cloud computing paradigm enables the provision of cost efficient IT-services by leveraging economies of scale and sharing data center resources efficiently among multiple independent applications and customers. However, the sharing of resources leads to possible interference between users and performance problems are one of the major obstacles for potential cloud customers. Consequently, it is one of the primary goals of cloud service providers to have different customers and their hosted applications isolated as much as possible in terms of the performance they observe. To make different offerings, comparable with regards to their performance isolation capabilities, a representative metric is needed to quantify the level of performance isolation in cloud environments. Such a metric should allow to measure externally by running benchmarks from the outside treating the cloud as a black box. In this article, we propose three different types of novel metrics for quantifying the performance isolation of cloud-based systems.We consider four new approaches to achieve performance isolation in Software-as-a-Service (SaaS) offerings and evaluate them based on the proposed metrics as part of a simulation-based case study. To demonstrate the effectiveness and practical applicability of the proposed metrics for quantifying the performance isolation in various scenarios, we present a second case study evaluating performance isolation of the hypervisor Xen.     

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。     

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。     

一种适应SaaS多租户模式的数据迁移方法

基于多租户技术的SaaS应用在数据安全性方面提供了三种数据隔离方式,不同数据隔离方式下的数据存储具有差异性和规律性,传统的数据迁移方案不能够有效地应对数据隔离方式变化的要求,为此需要开发针对于SaaS多租户应用的数据迁移工具来帮助服务提供商进行数据的移植。通过对SaaS多租户模式特点的分析,同时在参考传统数据迁移方案的基础上,提出基于XML数据验证前置以及表复制的数据迁移方案,能有效地解决SaaS多租户模式下的数据迁移需求。     

Risk assessment in service provider communities

Online service delivery undertaken between clients and service providers often incurs risks for both the client and the provider, especially when such an exchange takes place in the context of an electronic service market. For the client, the risk involves determining whether the requested service will be delivered on time and based on the previously agreed Service Level Agreement (SLA). Often risk to the client can be mitigated through the use of a penalty clause in an SLA. For the provider, the risk revolves around ensuring that the client will pay the advertised price and more importantly whether the provider will be able to deliver the advertised service to not incur the penalty identified in the SLA. This becomes more significant when the service providers outsource the actual enactment/execution to a data centre — a trend that has become dominant in recent years, with the emergence of infrastructure providers such as Amazon. In this work we investigate the notion of “risk” from a variety of different perspectives and demonstrate how risk to a service owner (who uses an external, third party data centre for service hosting) can be managed more effectively. A simulation based approach is used to validate our findings.     

面向产业链协同SaaS平台的业务流程定制技术

针对产业链协同软件即服务(SaaS)平台各企业群对业务流程个性化定制的需求,建立了业务流程与业务功能之间的映射关系和企业群与业务流程之间的定制关系,在此基础上构建了SaaS平台面向多企业群的业务流程定制模型,并提出了业务流程驱动规则和加载控制方法,以实现平台在应用过程中基于用户身份的业务流程动态加载支持。构建的业务流程定制模型和流程驱动规则以及相应的加载方法在汽车零部件产业链售后服务的外出申请审批流程的定制方面进行了应用验证,能实现SaaS平台运行过程中企业群对业务流程的个性化定制需求。     

面向产业链协同SaaS平台的多租户数据加密配置技术研究

针对产业链协同SaaS(software-as-a-service)平台以龙头企业为核心的多租户业务关联特性,并结合其面向企业联盟的独立数据库与共享数据库共享表相结合的数据存储特点,分析了产业链协同SaaS平台以龙头企业为核心的多租户业务数据的安全加密配置需求.通过建立产业链协同SaaS平台的多租户关联模型及面向企业联盟的业务数据加密配置模型,提出了龙头企业业务数据加密配置算法、加密配置元数据驱动的协作企业业务数据加密及提交算法,以及面向龙头企业和协作企业的业务数据查询的解密算法.模型和算法在汽车及零部件产业链协同SaaS平台零部件协同采购订单业务中进行了应用.通过龙头企业的配置,能实现不同联盟的个性化数据加密需求.     

面向服务的多租户访问控制模型研究

传统访问控制模型在多租户环境下无法满足租户之间的隔离访问以及对各租户的访问请求实行有效的统一管理的需求。为了在多租户环境下实现一套快速的、访问控制可配置的实施方案, 提出了一个面向服务的多租户访问控制模型。根据对多视图业务模型之间的关联进行分析, 识别出组织模型及其相关的资源模型。通过映射和转换将组织模型转换为面向服务的多租户访问控制模型, 并构建访问控制模块以配置和运行访问控制模型。最后以某交通物流信息平台为范例验证了该模型的可行性和有效性。验证结果表明, 模型能够在多租户环境下提供兼备快速配置与访问控制的实现支持。     

多租户集群中基于服务水平目标的调度机制

针对多租户集群中无法保证作业服务水平目标(SLO)的问题,提出了一种多租户场景下基于SLO的调度机制,其中包括优先调度算法和资源抢占算法。优先调度算法区别考虑超额使用资源的租户和未超额使用资源的租户,赋予后者的作业更高的优先级,在此前提下选择紧急度最高的作业,优先为其分配资源;资源抢占算法在资源受限的情况下,选择紧急度超过阈值的作业实施资源抢占,并根据租户的资源使用情况,在相应的运行作业范围内选择紧急度最低的作业,抢占其资源。实验结果表明,与现有保证公平的多租户调度器Capacity Scheduler相比,该调度机制可以在兼顾作业执行效率和租户间公平的前提下,显著提高作业的截止时间保证率,从而保证业务的服务水平目标。     

Interactive customization of ubiquitous Web applications

Ubiquitous environments pose new challenges for end users who often need to access their applications from various devices. In this paper we present a solution that allows users to easily customise and migrate interactive web applications starting with an existing desktop version. This is obtained through an intelligent infrastructure that enables users to select the relevant part of an interactive Web application in order to create a mobile version and migrate it.     

Explainable argumentation as a service

Gorgias Cloud offers an integrated application development environment that facilitates the development of argumentation-based systems over the internet. Argumentation is offered as a service in a way that this allows application systems to remotely access the argumentation service and utilize the results of the argumentative computation. Moreover, the service results include the explanation of the decision in both human and machine-readable formats. The first is useful for allowing the application validation to be done by experts, while the second is useful for development. It appears that this is the first case where argumentation is offered to developers in such an open and distributed way.     

Efficient network isolation and load balancing in multi-tenant HPC clusters

Multi-tenancy promises high utilization of available system resources and helps maintaining cost-effective operations for service providers. However, multi-tenant high-performance computing (HPC) infrastructures, like dynamic HPC clouds, bring unique challenges, both associated with providing performance isolation to the tenants, and achieving efficient load-balancing across the network fabric. Each tenant should experience predictable network performance, unaffected by the workload of other tenants. At the same time, it is equally important that the network links are balanced, avoiding network saturation. The network saturation can lead to unpredictable application performance, and a potential loss of profit for the cloud service providers.In this paper, we present two significant extensions to our previously proposed partition-aware fat-tree routing algorithm, pFTree, for InfiniBand-based HPC systems. First, we extend pFTree to incorporate provider defined partition-wise policies that govern how the nodes in different partitions are allowed to share network resources with each other. Second, we present a weighted version of the pFTree routing algorithm, that besides partitions, also takes node traffic characteristics into account to balance load across the network links more evenly. A comprehensive evaluation comprising both real-world experiments and simulations confirms the correctness and feasibility of the proposed extensions.     

Efficient synthesis of feature models

ContextVariability modeling, and in particular feature modeling, is a central element of model-driven software product line architectures. Such architectures often emerge from legacy code, but, creating feature models from large, legacy systems is a long and arduous task. We describe three synthesis scenarios that can benefit from the algorithms in this paper.ObjectiveThis paper addresses the problem of automatic synthesis of feature models from propositional constraints. We show that the decision version of the problem is NP-hard. We designed two efficient algorithms for synthesis of feature models from CNF and DNF formulas respectively.MethodWe performed an experimental evaluation of the algorithms against a binary decision diagram (BDD)-based approach and a formal concept analysis (FCA)-based approach using models derived from realistic models.ResultsOur evaluation shows a 10 to 1,000-fold performance improvement for our algorithms over the BDD-based approach. The performance of the DNF-based algorithm was similar to the FCA-based approach, with advantages for both techniques. We identified input properties that affect the runtimes of the CNF- and DNF-based algorithms.ConclusionsOur algorithms are the first known techniques that are efficient enough to be used on dependencies extracted from real systems, opening new possibilities of creating reverse engineering and model management tools for variability models.     

A conceptual model of service customization and its implementation

With the development of Internet and next generation networks in telecommunications, more and more new services are required to be introduced into networks. Introducing new services into traditional network is always associated with standardizing new protocols. The progress of protocol standardization usually takes several years, which cannot meet the increasing demands of the applications in Internet and next generation networks. Service customization in network systems may be one possible solution to cope with this problem. Based on the principle that network service is provided by interactions among protocol entities, this paper proposes a conceptual model of service customization (SECUM) by separating the service logic from protocol interactive logic within existing network architecture. The theory of Communicating Sequential Processes (CSP) is used to formalize the SECUM in order to locate exactly the service logic and to define precisely the SECUM. For validating the SECUM‘s usability in practical network systems, this paper also proposes an implementation model for SECUM: a component-based protocol implementation model (CPIM). CPIM discomposes protocol entity into application component, service component, message component and communication component. Service component associates application component with message component. Users or network managers can customize network services by configuring service component. The paper shows respectively the applications of SECUM and CPIM by proposing a customizable IP service model based on SECUM and describing an implementation of Session Initiation Protocol (SIP) based on CPIM. Compared with the existing service-customization techniques, SECUM is a service customization model internal to network system and may provide more powerful capabilities of service customization.     

Development of a novel cloud-based multi-tenant model creation service for automatic virtual metrology

AVM (Automatic Virtual Metrology) is the highest-level technology for VM (Virtual Metrology) applications from the perspective of automation. Its various automatic capabilities could facilitate fast factory-wide deployment and operations of VM systems. AVM systems have been successfully applied to the semiconductor, TFT-LCD, solar-cell, and machining industries for on-line monitoring the production quality of workpieces. However, in its past industrial applications, the model creation (MC) functionality of the existing AVM system encountered several limitations, such as being a standalone application and confined to be used in situ in a factory, no support for multiuser model creation, wasting computing resources, etc., which could diminish the applicability of the existing AVM system in current global and distributed manufacturing environments. Thus, this paper is dedicated to tackling the problem of how to systematically and effectively overcome MC-related limitations of the existing AVM system so that it can robustly support multiple users across factories to create their VM models simultaneously in distributed manufacturing settings. By leveraging the advantages of cloud computing and several IT technologies (including virtualization software, XML, Web Service, Multi-tenancy technique, and HTML5), this paper proposes a novel cloud-based multi-tenant model creation service (i.e., CMMCS) for AVM. The proposed CMMCS contains a cloud-based system architecture, functional frameworks of its key components, several functional mechanisms, and HTML5-based Web GUIs. Testing results in an industrial case study that creates VM models using the CMMCS for CNC machine tools in machining wheel rims of automobiles in a factory in Taiwan demonstrate that the CMMCS can allow multiple users from different tenants to simultaneously create their VM models, while enabling the MC cloud services to be more robust for processing MC requests, having higher CPU-usage rates in the underlying virtual machines, and achieving better cross-platform usage, compared to the original MC functionality. This paper has provided a feasible solution to systematically and effectively remedying the MC-related limitations of the existing AVM system. The existing VM-related literature mainly focused on the development of VM models. To our knowledge, no papers have coped with issues addressed in this paper by leveraging cloud computing. The results of this paper can be a useful reference for industrial practitioners to construct AVM systems which support multi-tenant or multiuser model creation.     

MDE and customization of modeling and simulation web applications

In this paper, we present a model-driven approach to construction of web-based collaborative environments that could be efficiently tailored to modeling and simulation needs of an arbitrary number of M&S application domains. To achieve broad applicability, our approach is based on general concepts and taxonomies in fields of Modeling and Simulation, Distributed Systems, and Collaborative Software. Such stable concepts constitute the collaborative Modeling and online Simulation (cMoS) framework. cMoS provides a general basis for a family of Web-Based M&S applications. Specific M&S applications are supported through customization of the variation points in cMoS. To enable efficient tailoring to specific applications during the operation phase, the variation points are not implicitly hardcoded as traditionally, but are explicitly expressed as models. The use of the resulting models is still limited due to a high barrier of their implementation. This barrier is sought to be amended by model-driven engineering (MDE): models of the variation points are computerized and their implementation is automatically generated. The end result is a model-driven and mostly programming free cMoS system adaptable to new M&S applications through abstract modeling of the variation points. The proposed framework and model-driven construction of a cMoS system are demonstrated. The system customization has been verified for a number of domains: Data Flow Diagrams (DFD), Discrete Event System Specification (DEVS), Process Interaction (PI) and Dynamic Traffic Routing (DTR). A demonstration of the latter is included in this paper. Generic cMoS functionality, such as modeling, collaborative sharing of conceptual models, online simulation and management of shared simulation resources is demonstrated as well.     

面向个性化定制的云制造服务平台的研发

随着个性化产品市场生产需求的增加,产品的定制程度越来越高,产品对制造企业的设计水平、制造能力、服务内容提出了较高的要求,而现有企业设计、生产制造、管理能力不足等问题已严重制约了个性化市场的发展。为了能够推动个性化定制的深入应用,结合云制造技术,提出了基于云制造服务平台的个性化定制服务模式和思想理念,构建了一种面向个性化定制的云制造服务平台,分析了平台的体系结构和工作流程,最后采用Apache服务器、PHP编程语言以及MySQL数据库对平台进行了搭建,对部分功能进行了说明,并以等高齿对数螺旋锥齿轮的设计过程为例,验证了依托平台进行个性化定制的可行性。