Cloud Computing

Mahavir’s Education TrustShah & Anchor Kutchhi Engineering College

A Seminar Report On

CLOUD COMPUTING

Submitted By:

TE-4(A-Batch)

03:- Akshay Badjate06:- Ankit Joshi12:- Dhaval Shah

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Cloud Computing

ACKNOWLEDGMENT

We are grateful to our seminar teacher Mrs. Manimala and Mrs. Sindhu, for supporting us at every stage of this project with her expertise and knowledge of the subject.

Also, we would like to express our sincere gratitude to our H.O.D., Prof. Uday Bhave for giving us the opportunity to enhance our knowledge in the present and futuristic subject like CLOUD COMPUTING.

We would also like to thank our peers for their valuable inputs and time that helped us in the making of this project.

Thanking you,

03:- Akshay Badjate06:- Ankit Joshi12:- Dhaval Shah

 

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TABLE OF CONTENTS

1. Introduction 4

2. Literature Survey 5

3. Brief Theory 6

4. Summary 8

4.1 Cloud Computing and SOA 8

4.1.1 Layered Architecture of SOCCA

4.1.2 Cloud Ontology Mapping Layer

4.2 Multi-tenancy Architecture (MTA) 10

4.3 SaaS and Some Problems with SaaS Implementation 12

4.3.1 Benefits Of The vSaaS Approach

4.3.2 Highlights of A vSaaS System

4.3.3 Streaming Delivery of Software

4.3.4 Desktop Merging

4.3.5 Mobile Device

5. Proposed Implementation 16

6. Conclusion 17

7. Future Work 18

8. References 19

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Cloud Computing

1. INTRODUCTION

Cloud computing is a model for enabling convenient on demand network access to a shared pool of configurable computing resources (e.g. networks, servers, storage, application and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. Cloud Computing is an emerging style of computing in applications, data, and IT resources are provided as services to users. Cloud computing drives cost reduction and simplification by consolidation and more efficient utilization of existing resources.

Cloud computing consists of various applications that include Software as a service (SaaS), Platform as a service(PaaS) and Infrastructure as a service(IaaS).Cloud Application services or “Software as a Service(SaaS)” deliver ‘software’ as a service over the Internet, eliminating the need to install and run the application on the customer’s own computers and simplifying maintenance and support. Cloud platform services or “Plat form as a service (PaaS)” deliver a computing platform and/or solution stack as a service, often consuming cloud infrastructure and sustaining cloud applications. It facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers.

Cloud infrastructure services or “Infrastructure as a Service (IaaS)” delivers computer infrastructure, typically a platform virtualization environment, as a service. Rather than purchasing servers, software, data center space or network equipment, clients instead buy those resources as an outsourced service. The service is typically billed on a utility computing basis and amount of resources consumed (and therefore the cost) will typically reflect the level of activity. It is an evolution of virtual private server offerings.

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2. LITERATURE SURVEY

Topic: Characteristics of Cloud Computing.

Cloud computing emerges as one of the hottest topic in field of information technology. Cloud computing is based on several other computing research areas such as HPC, virtualization, utility computing and grid computing. In order to make clear the essential of cloud computing, we propose the characteristics of this area which make cloud computing being cloud computing and distinguish it from other research areas. The cloud computing has its own conceptional, technical, economic and user experience characteristics. The service oriented, loose coupling, strong fault tolerant, business model and ease use are main characteristics of cloud computing. Clear insights into cloud computing will help the development and adoption of this evolving technology both for academe and industry.

Reasons for Selection of the Paper:1. The paper lays a base to the introduction of the concept of Cloud Computing.2. This paper describes the key characteristics of cloud computing and gives an insight into its architecture.

Topic: Service Oriented Cloud Computing Architecture. This topic discusses about the relationship between the Service Oriented Architecture and Cloud Computing. It explains that SOA is all about defining an IT solution or architecture, while cloud computing is an architectural alternative. Cloud Computing offers a platform to deliver the services needed as a part of Service Oriented Architecture.

Reason for Selection of the Paper:1. This paper gives a comprehensive study of the Service Oriented Cloud Computing Architecture.2. It also gives an insight into the business models of Cloud Computing.

Topic: A Virtualization-based SaaS Enabling Architecture of Cloud Computing.

This Paper Draws Attention towards How to Provide Software as a Service through the Internet. It Is An Important Service Provided Through Cloud Computing. By SaaS Users Can Access Any Software Transparently with No Limitation on the Client OS or Device Capability. In This Paper an Approach Named vSaaS is discussed. The iVIC platform, in which vSaaS Approach Is Proposed is a virtual computing environment for HaaS and SaaS applications.

Reason for Selection of the Paper:1. This Paper Basically Describes SaaS which is a major feature of cloud computing.2. Moreover It Gives an In depth Insight into a New Approach named vSaaS for Providing This Important Feature of Cloud Computing.

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Cloud Computing

3. BRIEF THEORY

Cloud computing refers to the provision of computational resources on demand via a computer network, such as applications, databases, file services, email, etc. In the traditional model of computing, both data and software are fully contained on the user's computer; in cloud computing, the user's computer may contain almost no software or data (perhaps a minimal operating system and web browser only), serving as little more than a display terminal for processes occurring on a network of computers far away. Common shorthand for a provided cloud computing service (or even an aggregation of all existing cloud services) is "The Cloud".

The most common analogy to explain cloud computing is that of public utilities such as electricity, gas, and water. Just as centralized and standardized utilities free individuals from the difficulties of generating electricity or pumping water, cloud computing frees users from certain hardware and software installation and maintenance tasks through the use of simpler hardware that accesses a vast network of computing resources (processors, hard drives, etc.). The sharing of resources reduces the cost to individuals.

The phrase “cloud computing” originated from the cloud symbol that is usually used by flow charts and diagrams to symbolize the internet. The principle behind the cloud is that any computer connected to the internet is connected to the same pool of computing power, applications, and files. Users can store and access personal files such as music, pictures, videos, and bookmarks or play games or use productivity applications on a remote server rather than physically carrying around a storage medium such as a DVD or thumb drive. Almost all users of the internet may be using a form of cloud computing though few realize it. Those who use web-based email such as Gmail, Hotmail, Yahoo, a Company owned email, or even an e-mail client program such as Outlook, Evolution, Mozilla Thunderbird or Entourage that connects to a cloud email server. Hence, utilizing desktop applications to connect to your cloud email is still considered a cloud application.

Cloud computing shares characteristics with:

1. Autonomic computing  — computer systems capable of self-management. 2. Client–server model  – client–server computing refers broadly to any distributed

application that distinguishes between service providers (servers) and service requesters (clients).

3. Grid computing  — "a form of distributed computing and parallel computing, whereby a 'super and virtual computer' is composed of a cluster of networked, loosely coupled computers acting in concert to perform very large tasks."

4. Mainframe computer  — powerful computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, enterprise, and financial transaction processing.

5. Utility computing  — the "packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility, such as electricity.”

6. Peer-to-peer  – distributed architecture without the need for central coordination, with participants being at the same time both suppliers and consumers of resources (in contrast to the traditional client–server model).

7. Service-oriented computing  – Cloud computing provides services related to computing while, in a reciprocal manner, service-oriented computing consists of the computing techniques that operate on software-as-a-service.

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Key Characteristics:

Agility improves with users' ability to rapidly and inexpensively re-provision technological infrastructure resources.

Application Programming Interface (API) accessibility to software that enables machines to interact with cloud software in the same way the user interface facilitates interaction between humans and computers. Cloud computing systems typically use REST-based APIs.

Cost is claimed to be greatly reduced and in a public cloud delivery model capital expenditure is converted to operational expenditure. This ostensibly lowers barriers to entry, as infrastructure is typically provided by a third-party and does not need to be purchased for one-time or infrequent intensive computing tasks. Pricing on a utility computing basis is fine-grained with usage-based options and fewer IT skills are required for implementation (in-house).

Device and location independence enable users to access systems using a web browser regardless of their location or what device they are using (e.g., PC, mobile phone). As infrastructure is off-site (typically provided by a third-party) and accessed via the Internet, users can connect from anywhere.

Multi-tenancy enables sharing of resources and costs across a large pool of users thus allowing for: Centralization of infrastructure in locations with lower costs (such as real estate,

electricity, etc.) Peak-load capacity increases (users need not engineer for highest possible load-

levels) Utilization and efficiency improvements for systems that are often only 10–20%

utilized. Reliability is improved if multiple redundant sites are used, which makes well designed cloud

computing suitable for business continuity and disaster recovery. Scalability via dynamic ("on-demand") provisioning of resources on a fine-grained, self-

service basis near real-time, without users having to engineer for peak loads. Performance is monitored and consistent and loosely coupled architectures are constructed

using web services as the system interface. Security could improve due to centralization of data, increased security-focused resources,

etc., but concerns can persist about loss of control over certain sensitive data, and the lack of security for stored kernels. Security is often as good as or better than under traditional systems, in part because providers are able to devote resources to solving security issues that many customers cannot afford. However, the complexity of security is greatly increased when data is distributed over a wider area or greater number of devices and in multi-tenant systems which are being shared by unrelated users. In addition, user access to security audit logs may be difficult or impossible. Private cloud installations are in part motivated by users' desire to retain control over the infrastructure and avoid losing control of information security.

Maintenance of cloud computing applications is easier, because they do not need to be installed on each user's computer. They are easier to support and to improve, as the changes reach the clients instantly.

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Cloud Computing

4. SUMMARY

4.1 Cloud Computing and SOA: Cloud computing and SOA are related, specifically, SOA is an architectural pattern that guides business solutions to create, organize and reuse its computing components. On the other hand cloud computing is a set of enabling technology that services bigger, more flexible platforms for enterprise to build their SOA solutions. Several initiatives has been made in bridging SOA and cloud computing.

4.1.1 Layered Architecture of SOCCA: SOCCA is a layered architecture .Individual Cloud Provider Layer this layer resembles the current cloud implementations. Each cloud provider builds its own data centers that power the cloud services it provides. Each cloud may have its own proprietary virtualization technology or utilize open source virtualization technology, such as Eucalyptus. Eucalyptus is an open-source cloud computing framework that uses computational and storage infrastructure commonly available to academic research groups to provide a platform that is modular and open to experimental instrumentation and study.Eucalyptus is composed of several components that interact with one another through well-defined interfaces, inviting researchers to replace our implementations with their own or to modify existing modules. This is similar to Market Oriented Cloud Architecture in which a request dispatcher works

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with Virtual Machine Monitor and Service /App Governance Service to allocate the request to the available resources. The distinction from current cloudImplementations is that the cloud computing resources in SOCCA are componentized into independent services such as Storage Service, Computing Service and CommunicationService, with one-standardized interfaces, so they can be combined with services from other cloud providers to build cross platform virtual computer on the cloud.

4.1.2 Cloud Ontology Mapping Layer: Cloud providers might not conform to the standards rigidly; they might also have

implemented extra features that are not included in the standards. Cloud Ontology Mapping Layer exists to mask the differences among the different individual cloud providers and it help the migration of cloud application from one cloud provider and it can help the migration from one cloud to another.Several important ontology systems are needed:

1. Storage Ontology: It defines the concepts and terms related to data manipulation on the clouds2. Computing Ontology: It defines the concept and terms related to distribute computing on the clouds.3. Communication Ontology: It defines and terms related Communication schema among cloud the cloud, such as data encoding schema, message routing.

Cloud Broker Layer: Cloud brokers serve as the agents between individual cloud providers and SOA layer. Each major cloud service has an associated service broker type. Generally, cloud brokers need to fulfil the following tasks:

1. Cloud Provider Information Publishing: Individual cloud providers publish specifications and pricing info to the cloud brokers.

2. Ranking: Like the service brokers in SOA, cloud brokers also rank the cloud resources published. Services can be ranked in several categories such as price, reliability, availability, and security, etc.

3. Dynamic SLA Negotiation: Business is often dynamic, and the IT infrastructure has to be adaptive to accommodate the business needs, therefore to achieve the optimal ROI (Return of Investment). It’s often the case that the IT resources a business demands can be predicted.

4. On-Demand Provision Model: Most services experience seasonal or other periodic demand variation as well as some unexpected demand bursts due to external events. The only way to provide “on-demand” services, is to provision for them in advance. Accurate demand prediction and provision become critical for the successful of the cloud computing, which reduces the waste of utility purchase and can therefore save money using utility computing. We are investigating a demand prediction model and model the evolution of multi-tenant as a discrete time stochastic process.

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Cloud Computing

4.2 Multi-tenancy Architecture (MTA): SOCCA allows 3 different main multi-tenancy patterns. Authors discussed the left two multitenancy patterns: Multiple Application Instance (MAI) and Single Application Instance (SAI). The authors pointed out, the former does not scale as well as the latter, but it provides better isolation among different tenants. Within SOCCA, a new multitenant pattern becomes possible: Single Application Instance and Multiple Service Instances (SAIMSI).The motivation behind this pattern is that the workloads are often not distributed evenly among application components, and the performance of the single application instance is limited by the application components having lower throughput. Moreover, to enhance scalability, we want to reduce unnecessary duplications as much as possible as opposed to Multiple Application Instances pattern. The example application is composed by A, B, C, three services with C being the computing intensive component. With C being the bottleneck to support multiple tenants, 3 instances of C are created to balance the workloads. Note that the 3 instances of the services can also reside on different clouds. .

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Cloud Computing

Better scalability is not only benefit from the SAIMSI pattern, easy customizability is another gain. Suppose in the sample application, C is a payment service. Different tenants might have different payment method requirements, such as credit card, PayPal, or check. The application runtime environment (not described in this paper) will direct users of each tenant to the correct service instance according to tenants’ individual configuration. In the case that a future tenant has a payment requirement that cannot be met by the existing service instances, say money order, an according service instance can be easily plugged into the existing service instances group. The upcoming papers on multi-tenancy from our research group will provide more details on this topic.

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Cloud Computing

4.3 SaaS and Some Problems with SaaS Implementation:In recent years, the Software as a Service (SaaS), largely enabled by the Internet, has become an innovative software delivery model for enterprise and individuals to complete some business related tasks or personal tasks. Using the SaaS delivery model, software access has been simplified. However, there still exist three kinds of problems: First, the various legacy software is designed and developed for the desktop computer environment. If we want to make software web-accessible by multiple users, the redevelopment, even the redesign work, could turn out to be a massive work. Second, most current SaaS systems provide the software in the form of Web-based applications. The user experience and interaction is generally limited due to the presentation capability of Web-based software. In order to improve the interaction capability, extensions have been made to the HTTP and web protocols by some browsers. However these extensions will bring other compatibility problems between Web -based applications and browsers. Third, user data are stored and processed on the Internet even on the same server. Moreover, the security of the user data as well as the user’s privacy comes to be a new challenge.

4.3.1 Benefits Of The vSaaS Approach:Cloud computing is a newly developed computing model, which could use resources over Internet to finish the task by enterprise and personal. Compared with existing approaches, vSaaS can be beneficial in several ways. With the introduction of the virtual execution layer, the existing legacy software can be adopted without redevelopment or redesign work. The deployment work in the backend resource pool is dynamically conducted in an on-demand way without pre-installation. Moreover, we have a virtual display layer to separate the execution from the presentation of the software. Users can use different clients to access the software without consider the compatibility and performance problems.

4.3.2 Highlights of A vSaaS System:Software Dynamic Deployment:-In vSaaS system, software is provided as a service through the Internet. The software are deployed and executed on the back-end resource pool. Since different users will have different software usage requirement, it will be a big cost to maintain the dedicate environment for each user. Besides, the software may be conflict in the same environment due to libraries lack or version conflict. Benefiting from the OS-level virtualization, the software can be dynamically deployed and executed without installing them on the running environment.

4.3.3 Streaming Delivery of Software:Another benefit bring by the OS-level virtualization technology can be seen when the software is executed on the back-end resource pool, virtualized software can be launched without a fully download process. During the launch and execution processes, the needed part of the software can be delivered to the execution environment in a streaming manner. 4.3.4 Desktop Merging:Each user will have a virtual display instance. Virtual display instance is a virtual desktop, which can be used to merge all the presentation windows of software instances. After installing the client on the device, it will merge the virtual desktop together with the local desktop. Therefore, any remote running virtual software will just act like it is running locally.

4.3.5 Mobile Device:Access The software in our system is executed in the back-end resource pool, so there would not be any capability and version dependency on the client device system. Users can use their mobile devices easily to access the virtual display instance through the agent. Although a mobile client may sometime lose connection to the virtual display instance due to network problem, it will keep the status to wait until the client reconnects.

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To evaluate the functionality and performance of the vSaaS, we conduct experiments with four aspects in the real iVIC environment to explain the system behaviors. These experiments cover the major features of the vSaaS System. Besides, a comprehensive analysis based on the experiment results is presented.

Our experiment environment is based on an iVIC resource pool consisting of thirty-two blade server boxes, each with 2 Intel Xeon E5405(quad -core) 2.00GHz CPU, 4GB RAM, 73GB SATA hard disk, Debian Lenny(Linux kernel 2.6.26) operation system installed. All these nodes are interconnected with a gigabit Ethernet. We have also used a laptop with Intel Duo2 Core 2.4GB, 2GB RAM as a user client to access the software.

To evaluate the functions of software dynamic deployment and launch, we select 10 typical software for this experiment. All 10 software cover fields on daily-used software, such as, IM, network download tool, graphic editor, office suite and games. In this experiment, each software is dynamically deployed in a streaming way in the environment.

Initial Launch Bytes:-Here the initial launch bytes percentage of all software is collected. As shown in Figure Below, the software does not need the whole package to startup. Part of the package would be enough to launch the software. The average launch size percentage of the whole package bytes is about 10% to 20%, so our approaches have highly reduced the software deployment time to accelerate the launch of the software.

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We also perform a further experiment on the software loading process analysis. In this part, system log recorder is used to record all the file streaming related activities during the software launch. From the Figure 4, X axis is the logarithm of elapsed time(seconds), we can see that the 4 sample software, filezilla, medit ,skype and gpaint, have different launch curved shapes, because the dynamic libraries struts and sizes of the two samples are not the instinct. We also notice that there is still certain time-span before the launch finish during this idle time-span; the percentage of the package byes do not increase. So further, we can apply software prefetch feature to the software streaming in this idle time-span to accelerate the following execution of the software.Shows that the network delay has a highly effect on software launch time

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The third experiment is about the overhead of the OS-level virtualization in our system. The introducing of virtualization of core operation system components will increase the software launch time and execution latency. We use the launch time as the metric of the overhead. As shown in Table I: the delta of virtualized launch time and original launch time are at 0.1s level. This latency time caused by the overhead is acceptable in the real user scenarios. If the package download time and installation time of original launch method is considered, the vSaaS launch method is faster than the original launch method.

TABLE I. OVERHEAD OF OS-LEVEL VIRTUALIZATION

Software

Original Launch Virtualized

Delta(s)Time (s)

Launch Time (s)

skype 0.461 0.653 0.192

gpaint 0.191 0.358 0.167

medit 0.286 0.600 0.314

filezilla 1.139 1.535 0.396

scite 1.139 0.096 0.017

dvd95 0.181 0.356 0.175

Figure 5 shows the experiment about the effect of network delay on the software launch time. In this experiment, we have varied the network delay condition in through our network device and measured the impact on the software launch. The network round-trip delay time is set from 1ms to 10ms. The result

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5. PROPOSED IMPLEMENTATION

Install the Google App Engine NetBeans Plugin.

Follow the instructions given below:1. Start NetBeans.2. Note the NetBeans version number.3. Click Tools ->Plugin4. Select the Settings tab.5. Click the add button.6. Type “App Engine” (w/o quotes) into the Name field.7. If using NetBeans 6.7 paste

http://kenai.com/projects/nbappengine/downloads/download/1.0_NetBeans671/updates.xml into the URL field.

8. Click the OK button.9. Click on available Plugins.10. Select the Google App Engine plugins.11. Click Install button.

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6. CONCLUSION

Understanding a technical area as complex as cloud computing is not easy and requires identifying its fundamental characteristics. Clear concepts and terminology into cloud computing help but do not entirely solve the problem of how to design, develop and adopt a cloud computing system. Although based on previous research in HPC, virtualization, utility computing and grid computing, cloud computing still has its own characteristics which make cloud computing be cloud computing not anything else. This paper discusses the characteristics of cloud computing. The conceptional service oriented characteristic abstracts the details of cloud computing implementation. The loose coupling and strong fault tolerant stand for the main technical characteristics. Owning the business model is the key differentiation compared with other academic researches and helps cloud computing flourishing. The ease use user experience characteristic helps cloud computing being widely accepted by non-computer experts. We believe that these characteristics expose the essential of cloud computing and the development and adoption of this evolving technology will benefit from our work.

This paper proposed a service-oriented cloud computing architecture SOCCA that allows an application to run on different clouds and interoperate with each other. The SOCCA is a 4 layer architecture that supports both SOA and cloud computing. SOCCA supports easy application migration from one cloud to another and service redeployment to different clouds by separating the roles of service logic provider and service hosting/cloud providers. It promotes an open platform on which open standards, ontology are embraced. The paper also introduced related topics for future research, such as service demand prediction and SLA negotiation, and service request dispatching algorithms.

In this paper, we present the vSaaS, a platform of a virtual personal desktop environment base on OS-level virtualization and remote display technologies. The design principle and the highlight features of the vSaaS are detailed and a prototype solution is introduced. We have deployed the system in the real iVIC environment and performed a set of experiments. The result shows the feasibility and effectiveness of our solution.

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7. FUTURE SCOPES

As a part of the future work, first, we’d like to get detail of each characteristic especially the inner technologies. Second, we have more than ten years’ experience in HPC area and wish to syncretize the HPC into cloud computing. Third, the evaluation of cloud services is an interesting and valuable research subject.

The on-going work in This Field is focusing on the following three aspects: First, high-availability and fault-tolerance of the vProcess instance execution. Second, addition of prediction functions to the virtual software execution, thus accelerating the startup and execution of software. Third, Support for I/O device virtualization in the system. It is also very important for the software execution. Local devices can be virtualized and easily been accessed from the virtual software instances.

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8. REFERENCES

[1] IBM, “Google and IBM Announced University Initiative to Address Internet-Scale Computing Challenges,” http://www-03.ibm.com/press/us /en/ pressrelease/22414.wss.[2] Amazon, “Amazon Web Services,” http://aws.amazon.com/.[3] Google, “Google app Engine,” http://code.google.com/appengine/.[4] Salesforce, “CRM”, http://www.salesforce.com/.[5] searchcloudcomputing.com, “What is cloud computing?”http://searchcloudcomputing.techtarget.com/sDefinition/0,,sid201_gci1287881,00.html.[6] L.M. Vaquero, L.R. Merino, J. Caceres, and M. Lindner, “A break inthe clouds: towards a cloud definition,” ACM SIGCOMM ComputerCommunication Review, v.39 n.1, 2009.[7] Wikipedia, “Cloud computing,” http://en.wikipedia.org/wiki/Cloud computing.[8] Parascale. [Online]. http://www.parascale.com/[9] Elastra. [Online]. http://www.elastra.com/[10] Appirio. [Online]. http://www.appirio.com/[11] Rochwerger B et al., "The RESERVOIR Model and Architecture for,"IBM Systems Journal, 2009.[12] Christian Vecchiola, Xingchen Chu, and Rajkumar Buyya, "Aneka: ASoftware Platform for.NET-based Cloud Computing," in High Speed andLarge Scale Scientific Computing, 2010.[13] Rajkumar Buyya and Chee Shin Yeo, "Cloud Computing and EmergingIT Platforms: Vision, Hype, and Reality for Delivering Computing as the5th Utility," Future Generation Computer Systems, pp. 599-616, 2009.[14] Ying Huang et al., "A Framework for Building a Low Cost, Scalable andSecured Platform for Web-Delivered Business Services," , 2009[15] http://www.microsoft.com/windowsserver2003/technologies/terminalservices/default.mspx [accessed: December 12, 2009][16] http://www.sun.com/sunray/ [accessed: December 12, 2009][17] http://www.realvnc.com/ [accessed: December 12, 2009][18] J. Huai, Q. Li and C. Hu, “CIVIC: A Hypervisor Based VirtualComputing Environment,” Proceedings of the 2007International Conference on Parallel Processing Workshops,September, 2007[19] Y. Yu, H.K. Govindarajan, L. Lam and T. Chiueh"Applications of Feather-Weight Virtual Machine,"Proceedings of the 2008 ACM SIGPLAN/SIGOPSInternational Conference on Virtual Execution Environments(VEE08), Seattle WA., March, 2008.[20] X. Wei. 2006. Policy-Based Distributed Access Control forService Grid. Ph.D. dissertation, Beihang University, Beijing,China.[21] D. Ma, “The Business Model of "Software-As-A-Service"”,Proceedings of the 2007 IEEE International Conference onServices Computing (SCC07), Chicago, July, 2007

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