Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
  1. Home
  2. Browse subjects
  3. Computer Science
  4. Software Engineering and Development
  5. Content listing

Refine search

Refine search

Access:
Content type:
Publication date:
Apply   From and To filters
Subject: Show more
Journals Show more
Publishers: Show more
Societies Show more
Series: Show more
Collections: Show more

Actions for selected content:

Select all | Deselect all
  • View selected items
  • Export citations
  • Download PDF (zip)
  • Save to Kindle
  • Save to Dropbox
  • Save to Google Drive

Save Search

You can save your searches here and later view and run them again in "My saved searches".

Please provide a title, maximum of 40 characters.
Cancel
×

1810 results in Software Engineering and Development

Page 14 of 91

  • 21 - Mobile Cloud Computing and The Internet of Things

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 375-383

  • Summary

    The introduction of cloud computing has revolutionized the way of computing as it was being done. The impact of cloud computing technology has reached every corner of the world. It has introduced a new era where innovative technological advancements are emerging based on the strength and utility of cloud computing. Cloud computing may take some time to attain its full maturity but it has appeared as the biggest thing after the Internet. With its fast adoption in different domains and businesses, researchers are working on several issues of cloud computing. This concluding chapter of the book discusses such topics.

    This chapter briefly introduces two topics which are emerging as subjects of attraction after cloud computing. Mobile cloud computing is a technology that has opened the scope for overcoming the limitations of mobile computing through effective utilization of cloud computing. This makes mobile computing attractive and more useful for users, especially for billions of smart phone users.

    The most remarkable happening in the connectivity domain, after cloud computing is the ‘internet of things’. It promises to bring a revolution in human civilization by connecting living and non-living objects, and simplifying the act of collecting different information about them. All these digital innovations are propelling us towards a smarter planet.

    MOBILE CLOUD COMPUTING

    Mobile cloud computing (MCC) refers to the computing facility introduced by combining three fascinating technologies together: mobile computing, cloud computing and wireless communication. The emergence of MCC is followed by the explosive growth in uses of mobile devices, especially smart phones where cloud computing acts as a potential technology enabler for mobile services. The actual objective of MCC is to provide rich experience to users by offering cutting edge applications over a variety of mobile devices.

    The popularity of mobile devices which facilitates trouble-free communication and instant availability of information has made them an integral part of modern age human civilization. As a consequence, mobile cloud computing has emerged as an advanced step in the process of enriching mobile computing.

    Mobile Computing

    In simple words, mobile computing is a technology where computing-capable devices can transmit data without being connected to any device or network physically, even when in transit.

  • 19 - Cloud Management and a Programming Model Case Study

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 327-350

  • Summary

    Cloud computing does not imply any single technology. In short, a combination of multiple methodologies defines its architecture. The management of various aspects associated with this computing facility thus becomes very important case for successful outcome during its real-life implementations. Be it business delivery, or technical foundation of system development, the ‘service’ takes center stage in cloud computing. Consequently, cloud service management has become another important issue to be discussed in a new context.

    Most management activities in cloud are automated and SLA-driven. The service level agreement (SLA) thus plays an important role in the success of cloud computing. This chapter represents the lifecycle of SLA, apart from discussing the lifecycle of cloud service. Cloud management standards, tools and responsibilities of providers and consumers have also been discussed.

    This chapter also focuses on various programming models which are implemented on cloud. For this purpose a case study is represented with Aneka cloud platform which has a special feature of supporting multiple programming models. In this context, the chapter tries to revisit the cloud computing architecture once more and represents its design characteristics and few non-functional features as well from different angles.

    CLOUD ARCHITECTURE: REVISITED

    In very broad sense, the cloud computing system can be viewed as composition of two elements:

  • ▪ Client application at the front end

  • ▪ The cloud as the back end.

    • This is a very simple description as the backend comprises of several layers and abstractions. In most cases, the ‘client application’ at the frontend is a web browser through which cloud service interfaces (i.e. the portals) are accessed. Consumers can access the backend ‘cloud’ from any simple electronic device capable of running web browsers. Only prerequisite is the availability of network or Internet service. Quality of cloud service accessibility often depends on the speed of the network. But with advancements in the field of internet technology, speed is the least worrying factor nowadays.

    At the backend, the ‘cloud’ resides at some remote location generally being managed by some service providers. Reputed providers develop cloud service infrastructure at their own data centers. A provider can have multiple data centers at different geographic locations. As shown in Figure 19.1, this backend part can be seen as composition of two broad components: a cloud building platform and the cloud services.

  • 12 - Service-Oriented Architecture

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 207-223

  • Summary

    Management of any large system turns out to be a complex task if the architecture of the system is not flexible enough. It becomes difficult to deploy new functionalities, alter existing functionalities and integrate interoperability when an immovable system grows. As a solution, any large system should be decomposed into functional primitives for efficient and flexible management and this philosophy perfectly applies to cloud computing systems too.

    Clouds are generally heterogeneous and large in volume by their own nature. Hence, the flexible architecture (or flexible application architecture) is an essential criterion for making the computing system agile and capable of adjusting to quick changes in business strategy to take advantage in a competitive business market.

    The conventional application architectures are not designed to take advantage of infrastructural agility and diversity like a cloud. In cloud computing, applications perform best when they are built based on the paradigm called as ‘service-oriented architecture’ or SOA. This new architectural paradigm makes cloud applications flexible and specially shows its ability when the system grows over time. This chapter focuses on the philosophy of the service orientation, discusses its advantages and indicates how business application becomes agile with SOA implementation.

    THE PRE-SOA ERA

    Conventional computing systems were based on centrally-administrated architecture. But, such architecture was not appropriate for quick application development, neither was it designed to support rapid changes in functionality. Moreover, the processes of developing a new application system used to become complex, time-consuming and expensive.

    Then the concept of component based application development (CBD) model emerged. It had many goals similar to SOA. A component is a software object which is meant to interact with other components. Components are used to represent basic system functionalities, those which collaborate with other components. CBD promotes decomposition and reusability. It also increases productivity, quality and decreases the time-to-market. But interoperability is the issue that could not be handled with this system development model.

    With the widespread adoption of heterogeneous distributed systems, the need for application interoperability appeared. Heterogeneous system refers to the ability of integrating multiple type (cross architecture and/or cross vendor) of one or more computing resources (like processor) into a single computing environment. Cloud computing system is the ultimate outcome of heterogeneity.

  • 2 - Evolution and Enabling Technologies

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 19-37

  • Summary

    Cloud computing is not an abrupt innovation. Rather, it is a series of developments that have taken place over past few decades. Progresses in computing technology, starting from its early days, has slowly metamorphosed into cloud computing in this advanced era. Although the idea of cloud computing originated long ago, the concept could not materialize due to lack of necessary technological elements.

    Documentary evidence can be traced back to the 1960s, when John McCarthy (who coined the term ‘artificial intelligence’) wrote that ‘computation may someday be organized as a public utility.’ Since then, computing technology has gone through phases of development. Hardware and communication technology have been progressed, Internet has changed the world and at the same time, the web-based software architecture has also matured.

    As advancements in all associated fields have slowly overcome the limitations of earlier approaches, it has been possible to realize the dream of computing as the new measure of public utility. This chapter focusses on the evolution of cloud computing and discusses how generations have developed through stages like centralized computing, client server computing, distributed computing and grid computing on to cloud computing.

    THE EVOLUTION OF CLOUD COMPUTING

    Cloud computing is not an isolated development. Cloud technology has been matured over the years with constant advancements in the field of computing. The beginning can be traced back to a time when remote access to time-shared computing system became a reality. The realization of cloud computing has been closely linked with several other subsequent developments in the domain.

    Several decades of research, particularly in the domain of parallel and distributed computing, have paved the way for cloud computing.

    A thorough discussion about the development of cloud computing can never overlook the continuous innovations in the field of electronic and computing hardware. As the hardware technology evolved, so did the software. Beside these, with the advancements in communication protocols, network communication technology as well as Internet also played a vital role in this process. This section focusses on different phases of developments in the field of computing starting from the mainframe age and discusses how those progresses have contributed towards the growth of cloud computing.

  • 18 - Portability and Interoperability Issues

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 307-326

  • Summary

    Cloud computing is about using services provided by cloud vendors. When consumers invest effort and capital to develop their computing setup on some provider's service, one major concern for them is whether they can move to other cloud service in future, if necessary, with minimal disruption and effort. Can things once built over one cloud service be moved to another cloud service? This question arises since there are possibilities of vendor-lock-in, a situation where a consumer using one cloud service cannot easily move to a similar service delivered by a competitor company or service provider. All investments by a consumer may be in stake if computing setup created on one provider's service cannot be moved to other provider's service in future.

    An other concern comes in mind when consumers think about linking applications of two different cloud services together or, when it is required to link some on-premises non-cloud or cloud computing setup with a public cloud service. Such linking brings forth the issue of interoperability. Can applications of two different cloud environments be linked in such a way? This concern may worry the consumers.

    Consumers should have a clear understanding regarding these issues before moving into cloud. Such understanding enables one to take informed decisions when choices have to be made concerning technology, application or platform.

    Cloud adoption among the consumers also depends on how a cloud environment can address users’ concerns regarding portability and interoperability, apart from the issue of security.

    CHALLENGES IN THE CLOUD

    Although the cloud service offerings present a simplistic view of computing services to consumers, there are few critical issues to consider while moving into cloud. As already discussed, the prime challenges among these are the challenges associated with information security, privacy and compliance. The other vital challenges are related to issues of:

  • ▪ Portability and

  • ▪ Interoperability

    • These two issues arise while moving a system into cloud. The primary concerns during such initiatives are whether the system components are portable into a new environment or not. And then, there are concerns about the interoperability of the components of the existing system too.

  • 6 - Security Reference Model

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 95-110

  • Summary

    Security is one of the topmost concerns of any computing model and cloud computing is no exception. Consumers or enterprises moving into cloud need to feel secure about their computing facilities and more importantly about the data they are disclosing to service providers. This is a critical choice for enterprises accustomed to safeguarding data sitting in their own centers in the traditional way of computing. Cloud computing promotes the concept of working on proprietary data and applications outside their jurisdiction.

    It is often said that, ‘cloud computing is an excellent idea, but cloud security is not good’. The common perception is that the cloud services are not inherently secure. Cloud computing creates scope for scores of possibilities although like any other technology, there are some risks associated with it which can be overcome if understood correctly.

    A cloud computing environment can be formed in different ways and there can be several ‘cloud formations’. Each form is not suitable for every kind of business operations. Consumers must first understand which among these forms which is best-suited for their purpose. This little judgment can make the security of cloud computing even better than that of traditional in-house computing environments. This chapter focusses on these important aspects.

    If studied and designed appropriately, cloud computing causes no more threat to security than what exist in traditional computing.

    THE SECURITY CONCERN IN CLOUD

    Traditional computing systems used to create a security boundary by placing firewalls at the gateways through which the network used to communicate with the outer world. Firewall blocks unwanted traffic trying to access the network it protects and thus only authenticated accesses are allowed into the system. Thus, malicious accesses get blocked at firewalls in the traditional data centers in order to keep the system protected from outside threats.

    But this strategy only makes sense when all applications and data reside within one network of security perimeter. Traditional data centers allow perimeterized (i.e. within organization's own network boundary or perimeter) access to computing resources. But, the de-perimeterization (to open-up the interaction with outer network) and erosion of trust boundaries that was happening in enterprise applications, have been amplified and accelerated by cloud computing.

  • 11 - Load Balancing

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 190-206

  • Summary

    With appropriate capacity planning in cloud computing, the large pool of virtualized resources creates an illusion of an infinite source of computing resources. In the preceding chapters, it has been discussed how applications often need to scale to manage the varying workload and how resources are dynamically provisioned in order to meet the needs of scaling in cloud computing. It has also been discussed that horizontal scaling is more prepared for large scale scaling in distributed environment like cloud.

    Upon obtaining provisioned or de-provisioned dynamic resources, the horizontal scaling provides elasticity to cloud computing. But, this flexibility comes with lots of implementation complexity. Load balancing is the mechanism through which these features are implemented. Apart from these, as there are multiple resources available to serve a particular type of service request, and in a distributed computing environment it becomes necessary to distribute proportionately those service requests among the available resources so that none of them becomes overloaded and degrades the performance of the entire system. It is the run-time logic or algorithm of distributing the service requests that has to be capable of evenly distributing the workload. This chapter discusses different types of load balancing techniques along with their pros and cons. The possible parameters for consideration while working out load balancing algorithms have also been discussed. A properly-designed workload distribution and balancing architecture reduces resource underutilization, improves the performance of a system and also brings down the cost of computation.

    Load balancing is an important ingredient for building any dynamic, flexible, scalable and robustly-distributed computing architecture.

    LOAD BALANCING

    Load balancing in distributed computing systems is an essential technique to distribute processing and communication activities evenly across the resources in the network so that no single computing resource gets overloaded. Among different exercises, load balancing is especially important for applications which often deal with a large and unpredictable numbers of service requests. Load balancing is a technique that distributes load evenly among multiple computing resources such as processor, memory etc.

    Through load balancing, the incoming service requests are distributed among available computing resources. An efficient load balancing mechanism improves average resource utilization rate and therefore enhances the overall performance of a system.

  • 13 - File System and Storage

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 224-238

  • Summary

    The easy access to high-performance computing resources in cloud computing has not only made the process-intensive activities smarter but the data-intensive computing activities also have taken center stage. The nature of data have radically changed with this revolutionary utility service; hence their processing and storage requirements vary. Large data-sets are generated and produced everyday are sent for processing in the high-performance computing environments.

    Like the traditional storages, users can store and access multimedia files of various formats like text, image, audio and video in cloud also, but the storage requirements have been altered for efficient processing of the large data-sets which are produced in cloud every hour. The traditional enterprise level files and data storage systems were not sufficient to satisfy all of the data-intensive and high-performance computing requirements.

    Efficient file handling to support parallel and distributed operations of large data-sets needed an entirely new file system format. Hence, researchers and computing vendors have come up with suitable storage solutions to achieve optimal performance in cloud like high-performance environment. This chapter focuses on all of these advancements made to fulfill those requirements.

    Cloud computing promises high-performance. Hence, the file system and storage to support high-performance data processing are critical requirements of cloud environment.

    REQUIREMENTS OF DATA-INTENSIVE COMPUTING

    Data-intensive computing presents a challenge to computing systems in terms of delivering high-performance. Large volume complex data-sets cannot be processed centrally in a single node and require partitioning and distribution over multiple processing nodes. Thus, data-intensive computing is I/O-bound and requires rapid movements of data in large numbers. This requires appropriate management of data in transaction. Data modelling, partitioning, node assignment and accumulation are some of the critical parts of this computing. Consumers’ requirements and technical aspects related to the storage facility in high-performance computing environment are different from the traditional storage system in many ways. Traditional enterprise storage systems are no more sufficient to tackle those issues.

    Scalability and high-performance distributed data processing are complementary to each other. Distribution of large data-set among as-many-nodes as required for processing promotes scalability of the application. Suitable file systems are required to support this distribution and scaling proficiently. It has been observed that data-intensive computing often involves process-intensive computing too. Complex data-sets present challenges before the computing system.

  • Preface

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp xxi-xxii

  • Summary

    The future often arrives silently. In the digital world, cloud computing which emerged silently, has already made a significant place of its own and has shown enough potential to be the future of computing. The advantages it offers are plenty, and this is what makes cloud computing revolutionary.

    Books on this evolving subject started appearing in the market towards the end of the last decade. A handful of books have been published so far, and they provide useful resource material. While a few among them have been written in order to discuss conceptual aspects of the subject, others have been written from research or application perspective. As the research or application oriented books serve specific purposes only, they are not appropriate for general readers of the subject.

    Cloud computing is not a single technology; rather, it is a combination of multiple technologies. Hence, it is necessary to understand all those individual technologies in order to understand cloud computing as a whole. Many books have been written with their focus on some particular aspects of cloud computing, and thus, they have not been able to cover all the essential topics of cloud computing with equal importance. This book is written from conceptual perspective, for the sake of new learners of the subject, and it tries to fill the void for a book covering all the fundamentals in detail, with simplified explanations in a learner friendly manner.

    The author felt the need for such a book while teaching the subject to the undergraduate engineering students, as well as software professionals who wanted to develop a basic understanding of the subject. It is either inadequate coverage or a complex approach of most books available in the market, that makes it difficult for new learners to develop a clear conception about the various aspects of these technologies, and they therefore do not satisfy the fundamental queries of students. Thus, it is a lack of books covering all the fundamentals in detail which encouraged the author to write this book.

    The author is aware of the fact that computing and IT industry are fast merging into a singular cloud computing environment, and in the near future there will be a requirement for a large pool of workforce with sound insight into this subject.

  • 8 - Resource Pooling, Sharing and Provisioning

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 138-156

  • Summary

    Cloud computing delivers virtualized resources. In previous chapter, it has been discussed how virtualization technology has revolutionized the computing environment. It is important to note that in reality the virtualized resources are effective representations of actual physical resources. Cloud data centers maintain a large pool of physical computing resources which is presented in virtual mode as infrastructure service. This chapter focuses on how those resource pools are organized in cloud data centers.

    Resource sharing is another important feature of cloud computing. Any resource component from the pool of resources is not dedicatedly used to serve one particular user or application; rather they are shared among multiple users or applications. Through this increment in resource utilization rate, a comparatively smaller number of resources can serve a large number of users.

    Resource pooling, virtualization and sharing of resources ultimately converge to produce the dynamic behaviour of cloud systems. Cloud supplies the resources dynamically to users. This dynamic resource provisioning eliminates the need of permanent procurement of computing resources. This turns out to be a very effective technique as application demands or loads during computation do not remain same over a period of time.

    RESOURCE POOLING

    The utility service model of cloud computing requires to maintain huge amount of all types of computing resources to provide different services to consumers. For this purpose, cloud service providers create pool of computing resources. Effective pooling or grouping of resources requires appropriate system designing and architectural planning.

    Resource pooling in cloud needs setting up of strategies by provider for categorizing and managing resources. Before resource pooling concept appeared, earlier people used to maintain discrete and independent set of resources known as silos.

    In traditional computing model, the silos are made with very little or no inter-connections. On the other hand in cloud computing, the consumers use well-connected pool of computing resources. They gain almost no knowledge or control over the locations from where physical resources are allotted to them. In its out-of-best scenario, the providers sometimes ask for choice of geographic location (country or continent) from where a consumer wants to get resources. But this choice is only possible in case of large service providers who have data centers at multiple geographic locations around the world.

  • 4 - Cloud Computing Model

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 56-75

  • Summary

    The first three chapters of this book provide an overview of introductory cloud computing issues. Beginning with the discussion about limitations of traditional computing approach, it focused on the primary benefits of cloud computing adoption. The second chapter also explained how starting from the days of mainframe computers, cloud computing has matured over the years with continuous developments and reformations in the field of computing.

    With this basic understanding of the primary concepts and knowledge regarding the technological drivers behind cloud computing, it is now time to delve further. Now, it will be appropriate to understand the architectural model of cloud computing.

    In this chapter, the standard definitions and globally accepted NIST (National Institute of Standards and Technology) model of cloud computing have been explored in order to establish a baseline. NIST has identified five characteristics which have collectively revolutionized this computing model. Apart from these, different types of cloud deployments have also been discussed. Understanding the cloud deployment models is important as it is critical for making informed decisions so that appropriate cloud solution can be picked to satisfy personal or business needs.

    STANDARD CLOUD MODEL

    Cloud computing is a reality now and is being delivered commercially. Decades of research and several innovations have paved the way for its success. Though the concept surfaced several years back, the implementation of the concept has been possible through different phases of remodeling and renovation over the years.

    During its early days, the idea was defined in many ways by different sections of people as they presented it from their respective view points. Academicians, computer engineers, system architects, software developers, and consumers had their own ideas and suggestions about the models for this new approach of computing. All these proposals had several limitations as there were many aspects which had to be considered. Formation of a complete definition which could address all of these aspects was thus felt necessary. A standard model was also required as it becomes substantive for the advancement of any technology.

    Any technology needs a standard model for the conveniences of understanding uniformity.

  • 15 - Content Delivery Network

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 257-269

  • Summary

    In cloud computing everything moves around the globe through a huge network called Internet. All requested services and data from any public cloud are delivered to consumers via Internet. The delivery of the content from the source to the consumer may involve delays as the two may be far apart geographically from one another. This delay in content delivery in cloud computing could increase the response time barrier in acceptance of the technology. This delay may further increase due to heavy traffic over the network. And, studies have shown that delay in response time can cause huge business loss.

    Cloud computing is made not only for network-centric computing but also for network-centric content management. To serve the purpose of instant delivery of content via network to the consumers, technologists have introduced the concept of a dedicated network for faster content delivery. Content generators like cloud service providers can make use of these networks for efficiently delivering their content to millions of consumers across the globe.

    CONTENT DELIVERY IN THE CLOUD

    Content is any kind of data ranging from text to audio, image, video and so on. Delivering this content to any location at any time is a critical issue for the success of cloud services. Smooth delivery of content and a positive user experience have always been the prime concern of content makers and content providers in world-wide networked environment like cloud computing. The primary objective is to minimize the page (that is the content in a page) load time as studies have shown that even a delay of a second in page loading time can negatively affect customers’ experience significantly.

    Forecasting any failure in network delivery and overcoming it has always been a challenge for content suppliers and the scenario has turned more critical with the adoption of network-centric cloud computing environment. The network requirements for delivering content have changed extensively during the last decade when large volumes of multimedia content started pouring in and consumers’ expectation regarding content availability over Internet shot up.

    Computing performance over cloud-based services is very important to encourage cloud service adoption as consumers are accustomed to working on their personal work-stations in traditional way of computing.

  • 16 - Security Issues

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 270-292

  • Summary

    The introduction of cloud computing creates numerous benefits for consumers of computing services but it also has security concerns associated with it. In addition to most security risks present in the traditional computing environment, cloud computing brings a new set of security issues with it. These issues emerge basically due to the massive sharing of infrastructure and resources which is an inherent feature of the utility service model.

    A proper understanding of cloud architecture and appropriate selection of cloud deployment may reduce the security risks to a great extent. It is also important to understand that security maintenance is a combined effort for both the provider and the consumer of cloud. This chapter tries to focus on the security aspects of cloud from different service levels, apart from discussing the cloud security design principles and frameworks.

    Cloud-based security systems need to address all the basic needs of an information system like confidentiality, integrity, availability of information, identity management, authentication and authorization. These security requirements are not new, but cloud computing specific standpoint on these issues are essential to analyze as well as implement security in a cloud-based system.

    Despite its enormous benefits, security is one critical concern in cloud computing.

    CLOUD SECURITY

    For an enterprise, sharing infrastructure in cloud computing environment is like a person going to some public place with valuable belongings. Others with wrong intent may anytime target those valuable belongings. Similarly, moving sensitive files or data out of an enterprise's own network security boundary, in cloud computing, also causes security concerns. Hence, implementation of strong identity management and access control mechanism are important in cloud environment.

    Security is developing resistance to damage or protecting a system from any harm. Security is a major concern for any computing system and also for the cloud computing system too. Computing system security means protection of the system itself and also of the data that it stores.

    When an IT service consumer, be it an individual or an organization, migrates to cloud computing, especially in public cloud services; much of the computing infrastructure moves into the control of third-party cloud services providers.

  • 14 - Writing Effective Test Oracles

  • from Part 3 - Testing in Practice
  • Paul Ammann, George Mason University, Virginia, Jeff Offutt, George Mason University, Virginia
  • Book:
    Introduction to Software Testing
    Published online:
    28 May 2018
    Print publication:
    13 December 2016, pp 308-315

  • Summary

    The only true failure in life is not trying.

    Chapter 3 covered the foundations for how to automate tests. A key requirement of an automated test is that the test must encode the expected results, commonly known as the test oracle. When tests are run by hand, the expected results could be explicitly written in the textual test script or simply left up to the human tester to decide at run time. But an automated test must have that knowledge encoded as an explicit check such as with a JUnit assertion.

    Most of this book is concerned with designing effective test input values, but it turns out that many mistakes can and are made with test oracles. Test oracles must also exhibit effective revealability by striking a balance between checking too much (unnecessary cost) and checking too little (perhaps not revealing failures). Test oracles must solve problems with observability to obtain values that may not be readily available to the test script.

    This chapter first addresses the revealability problem by presenting knowledge on what values should be checked by an oracle in section 14.1. Then section 14.2 presents ideas on how to determine what the correct results are.

    WHAT SHOULD BE CHECKED?

    When tests used to be run by hand, the human tester sat at the computer and could immediately observe the results. The tester would use his or her judgment to directly decide whether the software behaved correctly, based on a well-informed understanding of the software requirements. If the tester could not see not enough outputs to make a confident decision about whether the software's behavior was correct, a tester with modest programming skills could improve observability by adding additional print statements, much like debugging. Naturally, testers sometimes missed failures, and this became one of the motivations for test automation. The idea is that an automated test does not blink, so is less likely to miss a failure when it occurs.

    Although a clear win for software quality, automation also meant that the test designer had to decide correct behavior for each test before the test was run, and then encode this correct behavior into the automated test. Chapter 3 introduced JUnit. It and its “xUnit” cousins are widely used in both academia and industry, thus we will use its oracle mechanism as a model.

Page 14 of 91