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{{Short description|Hosted software accessed by subscription}}
'''Software as a service''' ('''SaaS''') is a software application delivery model where a software vendor develops a web-native software application and hosts and operates (either independently or through a third-party) the application for use by its customers over the Internet. Customers pay not for owning the software itself but for using it. They use it through an API accessible over the Web and often written using [[Web service|Web Services]] or [[Representational State Transfer|REST]]. The term SaaS has become the industry preferred term, generally replacing the earlier terms [[Application service provider|Application Service Provider (ASP)]], [[On-demand|On-Demand]] and "[[Utility computing]]".
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{{redirect-distinguish|SaaS|Security as a service}}
'''Software as a service''' ('''SaaS''' {{IPAc-en|s|æ|s}}<ref>{{cite web|url=http://searchservervirtualization.techtarget.com/definition/How-do-you-pronounce-IT|last1=Panker|first1=Jon|last2=Lewis|first2=Mark|last3=Fahey|first3=Evan|last4=Vasquez|first4=Melvin Jafet|title=How do you pronounce IT?|work=TechTarget|access-date=24 May 2012|date=August 2007|archive-date=28 November 2016|archive-url=https://web.archive.org/web/20161128222956/http://searchservervirtualization.techtarget.com/definition/How-do-you-pronounce-IT|url-status=live}}</ref>) is a [[cloud computing]] service model where the provider offers use of [[application software]] to a client and manages all needed physical and software resources.{{sfn |Golding |2024|p=14}} SaaS is usually accessed via a [[web application]]. Unlike other [[software delivery]] models, it separates "the possession and ownership of software from its use".{{sfn|Dempsey |Kelliher|2018|p=2}} SaaS use began around 2000, and by 2023 was the main form of software application deployment.


Unlike most self-hosted software products, only one version of the software exists{{Citation needed|date=November 2024}} and only one [[operating system]] and configuration is supported. SaaS products typically run on rented [[infrastructure as a service]] (IaaS) or [[platform as a service]] (PaaS) systems including [[computer hardware|hardware]] and sometimes [[operating system]]s and [[middleware]], to accommodate rapid increases in usage while providing instant and continuous availability to customers. SaaS customers have the abstraction of limitless computing resources, while [[economy of scale]] drives down the cost. SaaS architectures are typically [[multi-tenant]]; usually they share resources between clients for efficiency, but sometimes they offer a siloed environment for an additional fee. Common SaaS revenue models include [[freemium]], [[subscription]], and usage-based fees. Unlike traditional software, it is rarely possible to buy a perpetual license for a certain version of the software.
==SaaS Architecture==
===History===
The concept of "software as a service" started to circulate in 2000/2001, associated with firms such as [[Citrix Systems]].<ref>[http://www.brainstorm-group.com/bsgweb/0900EBS.asp Note from an eBusiness Strategy conference] (September 2000)</ref><ref>[http://www.aspnews.com/analysis/analyst_cols/article.php/709821 Engines Emerge That Will Drive Software as a Service] (March 2001)</ref><ref>[http://software.silicon.com/webservices/0,39024657,11025074,00.htm Citrix Ditches ASP tag] (June 2001)</ref> The [[CamelCase|camelback acronym]] "SaaS" came into wide use after its first use in a non-profit conference on the subject in March of 2005<ref>[http://www.sdforum.org/saas2005]</ref>.


There are no specific [[software development]] practices that distinguish SaaS from other application development, although there is often a focus on frequent [[software testing|testing]] and releases.
===Philosophy of SaaS===
As a term, SaaS is generally associated with business software and is typically thought of as a low-cost way for businesses to obtain the same benefits of commercially licensed, internally operated software without the associated complexity and high initial cost. Consumer-oriented web-native software is generally known as [[Web 2.0]] and not as SaaS. Many types of software are well suited to the SaaS model, where customers may have little interest or capability in software deployment, but do have substantial computing needs. Application areas such as Customer Relations Management, Video Conferencing, Human Resources, Accounting and Email are just a few of the initial markets showing SaaS success. The distinction between SaaS and earlier applications delivered over the Internet is that SaaS solutions were developed specifically to leverage web technologies such as the browser, thereby making them web-native.


==Cloud computing==
===Key characteristics of software delivered by SaaS ===
{{main|Cloud computing}}
The key characteristics of SaaS software, according to [[International Data Corporation|IDC]], include:<ref name="IDC">{{cite web| title=2005 Software as a Service Taxonomy and Research Guide| first=Erin| last=Traudt| coauthors=Amy Konary| url=http://www.idc.com/getdoc.jsp?containerId=33453&pageType=PRINTFRIENDLY#33453-S-0001| accessdate=2006-08-25| year=2005| month=June| publisher=IDC| pages=7}}</ref>
[[File:Comparison of on-premise, IaaS, PaaS, and SaaS.png|thumb|Comparison of on-premise, IaaS, PaaS, and SaaS|upright=2.4|center]]
[[Infrastructure as a service]] (IaaS) is the most basic form of [[cloud computing]], where infrastructure resources—such as physical computers—are not owned by the user but instead leased from a cloud provider. As a result, infrastructure resources can be increased rapidly, instead of waiting weeks for computers to ship and set up. IaaS requires time and expertise to make use of the infrastructure in the form of [[operating system]]s and [[Application software|application]]s.{{sfn|Rosati |Lynn|2020|p=22}} [[Platform as a service]] (PaaS) includes the operating system and [[middleware]], but not the applications.{{sfn|Rosati |Lynn|2020|p=23}}{{sfn|Ibrahim ''et al.''|2023|p=258}} SaaS providers typically use PaaS or IaaS services to run their applications.{{sfn|Rosati |Lynn|2020|p=23}}


Without IaaS, it would be extremely difficult to make an SaaS product scalable for a variable number of users while providing the instant and continual availability that customers expect.{{sfn|Dempsey |Kelliher|2018|p=17}} Most end users consume only the SaaS product and do not have to worry about the technical complexity of the physical hardware and operating system.{{sfn|Dempsey |Kelliher|2018|pp=17–18}} Because cloud resources can be accessed without any human interactions, SaaS customers are provided with the abstraction of limitless computing resources, while [[economy of scale]] drives down the cost.{{sfn|Dempsey |Kelliher|2018|p=19}} Another key feature of cloud computing is that software updates can be rolled out and made available to all customers nearly instantaneously.{{sfn|Dempsey |Kelliher|2018|p=33}} In 2019, SaaS was estimated to make up the plurality, 43 percent, of the cloud computing market while IaaS and PaaS combined account for approximately 25 percent.{{sfn|Rosati |Lynn|2020|p=20}}
* network-based access to, and management of, commercially available (i.e., not custom) software
* activities that are managed from central locations rather than at each customer's site, enabling customers to access applications remotely via the [[WWW|Web]]
* application delivery that typically is closer to a one-to-many model (single instance, [[multitenant|multi-tenant]] architecture) than to a one-to-one model, including architecture, pricing, partnering, and management characteristics
* centralised feature updating, which obviates the need for downloadable patches and upgrades.


==History==
SaaS applications are generally priced on a per-user basis, sometimes with a relatively small minimum number of users, and often with additional fees for extra bandwidth and storage. SaaS revenue streams to the vendor are therefore lower initially than traditional software license fees, but are also recurring, and therefore viewed as more predictable, much like maintenance fees for licensed software.
In the 1960s, [[Computer multitasking|multitasking]] was invented, enabling [[mainframe computer]]s to serve multiple users simultaneously. Over the next decade, [[timesharing]] became the main business model for computing, and [[cluster computing]] enabled multiple computers to work together.{{sfn|Dempsey |Kelliher|2018|p=19}} Cloud computing emerged in the late 1990s with companies like [[Amazon (company)|Amazon]] (1994), [[Salesforce]] (1999), and Concur (1993) offering [[Internet]]-based [[Application software|application]]s on a pay-per-use basis. All of these focused on a single product to seize a high [[market share]].{{sfn|Dempsey |Kelliher|2018|pp=23, 31}} Beginning with [[Gmail]] in 2004, email services were some of the first SaaS products to be mass-marketed to consumers.{{sfn|Watt|2023|p=8}} The market for SaaS grew rapidly throughout the early twenty-first century.{{sfn|Dempsey |Kelliher|2018|pp=24, 32}}{{sfn|Rosati |Lynn|2020|p=20}} Initially viewed as a technological innovation, SaaS has come to be perceived more as a business model.{{sfn|Dempsey |Kelliher|2018|p=35}} By 2023, SaaS had become the primary method that companies deliver applications.{{sfn|Watt|2023|p=4}}


Popular consumer SaaS products include all [[social media]] websites, email services like [[Gmail]] and its associated [[Google Docs Editors]],{{sfn|Watt|2023|pp=4, 8}} [[Skype]], [[Dropbox]],{{sfn|Clohessy ''et al.''|2020|p=40}} and entertainment products like [[Netflix]] and [[Spotify]].{{sfn|Watt|2023|p=9}} Enterprise SaaS products include [[Salesforce]]'s [[customer relationship management]] (CRM) software, [[SAP Cloud Platform]], and [[Oracle Cloud Enterprise Resource Planning]].{{sfn|Clohessy ''et al.''|2020|p=40}}
=== ASP versus SaaS ===


==Revenue models==
The reason for moving away from the term ASP or [[application service provider]] is that the ASP generation was merely traditional [[client-server]] applications with [[HTML]] [[frontend]]s added as an afterthought. These applications were [[hosting|hosted]] by third-parties who ordinarily did not have application development expertise, but were only managing servers. Because the applications were not written as net-native applications, performance was poor and application updates were no better than self managed applications. By comparison, current net-native SaaS applications or independent portions are updated regularly, many daily.
Some SaaS providers offer free services to consumers that are funded by means such as [[advertising]], [[affiliate marketing]], or selling consumer data.{{sfn|Dempsey |Kelliher|2018|p=48}} One of the most popular models for Internet start-ups and mobile apps is [[freemium]], where the company charges for continued use or a higher level of service. Even if the user never upgrades to the paid version, it helps the company capture a higher market share and displace customers from a rival.{{sfn|Dempsey |Kelliher|2018|pp=61-63}} However, the company's hosting cost increases with the number of users, regardless of whether it is successful at enticing them to use the paid version.{{sfn|Dempsey |Kelliher|2018|pp=63-64}} Another common model is where the free version only provides demonstration ([[crippleware]]). Online marketplaces may charge a fee on transactions to cover the SaaS provider costs.{{sfn|Dempsey |Kelliher|2018|p=48}} It used to be more common for SaaS products to be offered for a one-time cost, but this model is declining in popularity.{{sfn|Dempsey |Kelliher|2018|p=48}} A few{{sfn|Dempsey |Kelliher|2018|p=48}} SaaS products have [[open source]] code, called open SaaS. This model can provide advantages such as reduced deployment cost, less vendor commitment, and more [[Portability (computer science)|portable]] applications.{{sfn|Bhandari |Gupta|2019|p=21}}


The most common SaaS revenue models involve subscription and pay for usage.{{sfn|Dempsey |Kelliher|2018|pp=48, 57}} For customers, the advantages include reduced upfront cost, increased flexibility, and lower overall cost compared to traditional software with perpetual [[software license]]s.{{sfn|Clohessy ''et al.''|2020|pp=40-41}} In some cases, the steep one-time cost demanded by sellers of traditional software were out of the reach of [[Small and medium-sized enterprises|smaller business]]es, but pay-per-use SaaS models makes the software affordable.{{sfn|Dempsey |Kelliher|2018|p=2}} Usage may be charged based on the number of users, transactions, amount of storage spaced used, or other metrics.{{sfn|Dempsey |Kelliher|2018|p=57}} Many buyers prefer pay-per-usage because they believe that they are relatively light users of the software, and the seller benefits by reaching occasional users who would otherwise not buy the software.{{sfn|Dempsey |Kelliher|2018|p=57}} However, it can cause revenue uncertainty for the seller and increases the overhead for [[Electronic billing|billing]].{{sfn|Dempsey |Kelliher|2018|pp=57-58}}
This gradual shift in the terminologies also is a direct reflection of the change in the business requirements demanded by clients. The focus in SaaS is more on what the customer wants rather than what the vendor could give as was the case in an ASP.


The subscription model of SaaS offers a continuing and renewable revenue stream to the provider, although vulnerable to cancellation.{{sfn|Dempsey |Kelliher|2018|p=2}} If a significant number are cancelled, the viability of the business can be placed in jeopardy.{{sfn|Dempsey |Kelliher|2018|p=2}} The ease of canceling a subscription and switching to a competitor leave customers with the leverage to get concessions from the seller.{{sfn|Dempsey |Kelliher|2018|p=11}} While recurring revenues can help the business and attract investors, the need for [[customer service]] skills in convincing the customer to renew their subscription is a challenge for providers switching to subscription from other revenue models.{{sfn|Dempsey |Kelliher|2018|p=66}}
Early SaaS approaches were [[application service provider]]s (ASPs) who ran a turnkey application on behalf of their clients. But ASPs generally did not build the application themselves; rather, they took an off-the-shelf application (such as a messaging platform, an enterprise resource planning tool, or a salesforce automation package) and ran it for customers.{{Fact|date=July 2007}}


==Adoption==
SaaS vendors typically use a ''[[multitenancy|multi-tenant architecture]]'', meaning that multiple customers are running the same software, but with a virtually separate data. ASPs by comparison, merely deployed one application instance on a server for each customer, just as a customer would deploy internally. This inability to scale this kind of business model may be cited as one of the reasons for the failure of the ASP model. It's reasonable to assume that multi-tenant architecture simplifies application management for the vendor. The multi-tenant model also simplifies the value for all customers since upgrades are instantaneous available across the entire platform. The notion that one customer (tenant) can excessively burden the service is baseless and absent of fact. The largest current deployment of SaaS is by [[Wachovia]], using a SuccessFactors solution with 85,000 users, and the company anticipates an additional 25,000 users over the next two years.<ref>{{cite web| title=SuccessFactors Announces One of the Largest Software-as-a-Service Deployments Ever; 85,000 Seat| url=http://www.successfactors.com/press-releases/135/| accessdate=2007-06-09| year=2007| month=April}}</ref>
SaaS products are typically accessed via a [[web browser]] as a publicly available [[web application]].{{sfn|Garbis |Chapman|2021|p=185}}{{sfn|Watt|2023|p=4}} This means that customers can access the application anywhere from any device without needing to [[Installation (computer programs)|install]] or [[software update|update]] it.{{sfn|Watt|2023|p=4}}{{sfn|Kinnunen|2022|pp=123-124}} SaaS providers often try to minimize the difficulty of signing up for the product.{{sfn |Golding |2024|p=18}} Many capitalize on the service-oriented structure to respond to customer feedback and evolve their product quickly to meet demands. This can enable customers to believe in the continued improvement of the product and help the SaaS provider get customers from an established traditional software company that likely can offer a deeper feature set.{{sfn |Golding |2024|p=20}}{{sfn|Watt|2023|p=15}}


Although on-premises software is often less secure than SaaS alternatives,{{sfn|Watt|2023|pp=6, 16}} security and privacy are among the main reasons cited by companies that do not adopt SaaS products.{{sfn|Ibrahim ''et al.''|2023|pp=264, 266, 268}} SaaS companies have to protect their publicly available offerings from abuse, including [[denial-of-service]] attacks and hacking.{{sfn|Garbis |Chapman|2021|p=186}} They often use technologies such as [[access control]], [[authentication]], and [[encryption]] to protect [[data confidentiality]].{{sfn|Ibrahim ''et al.''|2023|pp=264, 266, 268}} Nevertheless, not all companies trust SaaS providers to keep sensitive data secured.{{sfn|Ibrahim ''et al.''|2023|pp=264, 266, 268}} The vendor is responsible for [[software update]]s, including [[software patch|security patches]], and for protecting the customers' data.{{sfn|Kinnunen|2022|pp=123-124}} SaaS systems inherently have a greater [[Latency (engineering)|latency]] than software run on-premises due to the time for network packets to be delivered to the cloud facility. This can be prohibitive for some uses, such as time-sensitive industrial processes or warehousing.{{sfn|Kinnunen|2022|pp=137, 139}}
==SaaS adoption==
=== Drivers for SaaS adoption ===


The rise of SaaS products is one factor leading many companies switched from budgeting for [[IT]] as a [[capital expenditure]] to an [[operating expenditure]].{{sfn|Tallon ''et al.''|2020|p=2}} The process of migration to SaaS and supporting it can also be a significant cost that must be accounted for.{{sfn|Kinnunen|2022|p=124}}{{sfn|Dempsey |Kelliher|2018|p=66}}
The traditional rationale for outsourcing of IT systems is that by applying economies of scale to the operation of applications, a service provider can offer better, cheaper, more reliable applications than companies can themselves.
The use of SaaS-based applications has grown dramatically, as reported by many of the analyst firms that cover the sector. But it’s only in recent years that SaaS has truly flourished. Several important changes to the way we work have made this rapid acceptance possible.
*Everyone has a computer: Most information workers have access to a computer and are familiar with conventions from mouse usage to web interfaces. As a result, the learning curve for new, external applications is lower and less hand-holding by internal IT is needed.
*Computing itself is a commodity: In the past, corporate mainframes were jealously guarded as strategic advantages. More recently, the applications were viewed as strategic. Today, people know it’s the business processes and the data itself—customer records, workflows, and pricing information—that matters. Computing and application licenses are cost centers, and as such, they’re suitable for cost reduction and outsourcing. The adoption of SaaS could also drive Internet-scale to become a commodity.<ref>http://www.saasblogs.com/2006/09/26/scale-as-a-commodity-2/ SaaSBlogs: Scale as a Commodity</ref>
*Applications are standardized: With some notable, industry-specific exceptions, most people spend most of their time using standardized applications. An expense reporting page, an applicant screening tool, a spreadsheet, or an e-mail system are all sufficiently ubiquitous and well understood that most users can switch from one system to another easily. This is evident from the number of web-based calendaring, spreadsheet, and e-mail systems that have emerged in recent years.
*Parametric applications are usable: In older applications, the only way to change a workflow was to modify the code. But in more recent applications—particularly web-based ones—significantly new applications can be created from parameters and macros. This allows organizations to create many different kinds of business logic atop a common application platform. Many SaaS providers allow a wide range of customization within a basic set of functions.
*A specialized software provider can target a global market: A company that made [[Human Resource Management Systems|software for human resource management]] at boutique hotels might once have had a hard time finding enough of a market to sell its applications. But a hosted application can instantly reach the entire market, making specialization within a vertical not only possible, but preferable. This in turn means that SaaS providers can often deliver products that meet their markets’ needs more closely than traditional “shrinkwrap” vendors could.
*Web systems are reliable enough: Despite sporadic outages and slow-downs, most people are willing to use the public Internet, the Hypertext Transfer Protocol and the TCP/IP stack to deliver business functions to end users.
*Security is sufficiently well trusted and transparent: With the broad adoption of SSL organizations have a way of reaching their applications without the complexity and burden of end-user configurations or VPNs.
*Availability of enablement technology: According to IDC,<ref name="IDC">{{cite web| title=2005 Software as a Service Taxonomy and Research Guide| first=Erin| last=Traudt| coauthors=Amy Konary| url=http://www.idc.com/getdoc.jsp?containerId=33453&pageType=PRINTFRIENDLY#33453-S-0005| accessdate=2006-08-25| year=2005| month=June| publisher=IDC| pages=7}}</ref> organizations developing enablement technology that allow other vendors to quickly build SaaS applications will be important in driving adoption. Because of SaaS' relative infancy, many companies have either built enablement tools or platforms or are in the process of engineering enablement tools or platforms. A Saugatuck study shows that the industry will most likely converge to three or four enablers that will act as SaaS Integration Platforms (SIPs).<ref name="Saugatuck">{{cite web| title=SaaS 2.0: Saugatuck Study Shows Rapid SaaS Evolution to Business Platforms| url=http://pdfserver.prweb.com/pdfdownload/377561/pr.pdf#search=%22saugatuck%20%20sip%20saas%20filetype%3Apdf%22.| accessdate=2006-09-01 | year=2006| month=April}}</ref>
* Wide Area Network's bandwidth has grown drastically following the Moore's Law (more than 100% increase each 24 months) and is about to reach slow local networks bandwidths. Added to network quality of service improvement this has driven people and companies to trustfully access remote locations and applications with low latencies and acceptable speeds.


==Development==
===SaaS Maturity Levels===
[[File:SaaS architecture.jpg|thumb |A SaaS architecture. All customers are running the same version of the software on the same platform.{{sfn |Golding |2024|p=25}}]]
A challenge for SaaS providers is that demand is not known in advance. Their system must have enough slack to be able to handle all users without turning any away, but without paying for too many resources that will be unnecessary. If resources are static, they are guaranteed to be wasted during non-peak time.{{sfn|Dempsey |Kelliher|2018|p=36}} Sometimes cheaper off-peak rates are offered to balance the load and reduce waste.{{sfn|Dempsey |Kelliher|2018|p=37}} The expectation for continuous service is so high that outages in SaaS software are often reported in the news.{{sfn|Dempsey |Kelliher|2018|p=39}}


There are not specific [[software development]] practices that differentiate SaaS from other application development.{{sfn|Watt|2023|p=11}} SaaS products are often released early and often to take advantage of the flexibility of the SaaS delivery model.{{sfn|Watt|2023|p=16}} [[Agile software development]] is commonly used to support this release schedule.{{sfn|Younas ''et al.''|2018|p=142}} Many SaaS developers use [[test-driven development]], or otherwise emphasize frequent [[software testing]], because of the need to ensure availability of their service and rapid deployment.{{sfn|Watt|2023|pp=11-12, 16}} [[Domain-driven design]], in which business goals drive development, is popular because SaaS products must sell themselves to the customer by being useful.{{sfn|Watt|2023|p=12}} SaaS developers do not know in advance which devices customers will try to access the product from—such as a desktop computer, tablet, or smartphone—and supporting a wide range of devices is often an important concern for the [[Front-end web development|front-end development]] team.{{sfn|Watt|2023|pp=13-14}} [[Progressive web application]]s allow some functionality to be available even if the device is offline.{{sfn|Watt|2023|p=13}}
Architectures for SaaS can generally be associated with one of four primary categories, or "maturity" levels.<ref name="Microsoft">{{cite web| title=Architecture strategies for catching the long tail| url=http://msdn2.microsoft.com/en-us/library/aa479069.aspx| accessdate=2006-04-01 | year=2006| month=April}}</ref> Although the definition of these maturity levels arose from Microsoft, the styles and levels are agnostic of implementation mechanism, and purely identify tangible architectural concepts that any web-native SaaS application can relate to.


SaaS applications predominantly offer integration protocols and [[application programming interface]]s (APIs) that operate over a [[wide area network]].{{sfn|Manvi|Shyam|2021|p=105}}
The first level of maturity is similar to the traditional application service provider (ASP) model of software delivery, dating back to the 1990s. At this level, each customer has its own customized version of the hosted application, and runs its own instance of the application on the host's servers.
===Architecture===
SaaS architecture varies significantly from product to product.{{sfn |Golding |2024|p=47}} Nevertheless, most SaaS providers offer a [[Multitenancy|multi-tenant]] architecture.{{sfn|Garbis |Chapman|2021|p=185}} With this model, a single [[software versioning|version]] of the application, with a single [[computer configuration|configuration]] ([[computer hardware|hardware]], [[computer network|network]], [[operating system]]), is used for all customers ("tenants").{{sfn|Golding|2024|pp=25-26}} This means that the company does not need to support multiple versions and configurations.{{sfn|Watt|2023|p=4}} The architectural shift from each customer running their own version of the software on their own hardware affects many aspects of the application's design and security features.{{sfn|Golding|2024|pp=25-26}} In a multi-tenant architecture, many [[System resource|resources]] can be used by different tenants or shared between multiple tenants.{{sfn |Golding |2024|p=26}}


[[File:Application and control planes of a SaaS product.png|thumb|upright=2|Application and control planes of a SaaS product|center]]
At the second level of maturity, the vendor hosts a separate instance of the application for each customer (or tenant). Whereas in the first level each instance is individually customized for the tenant, at this level, all instances use the same code implementation, and the vendor meets customers' needs by providing detailed configuration options that allow the customer to change how the application looks and behaves to its users.
The structure of a typical SaaS application can be separated into application and control planes.{{sfn |Golding |2024|p=27}} SaaS products differ in how these planes are separated, which might be closely integrated or loosely coupled in an event- or message-driven model.{{sfn |Golding |2024|p=44}} The control plane is in charge of directing the system and covers functionality such as tenant onboarding, billing, and metrics, as well as the system used by the SaaS provider to configure, manage, and operate the service.{{sfn |Golding |2024|p=27}} Many SaaS products are offered at different levels of service for different prices, called [[tiering]].<!-- redlink, notable pricing strategy --> This can also affect the architecture for both planes, although it is commonly placed in the control plane.{{sfn |Golding |2024|p=40}} Unlike the application plane, the services in the control plane are not designed for multitenancy.{{sfn |Golding |2024|p=28}}


[[File:Tenant routing for SaaS example.png|thumb|An example architecture where some services are shared, while others are allocated on a per-tenant basis{{sfn |Golding |2024|p=38}}|upright=2|center]]
At the third level of maturity, the vendor runs a single instance that serves every customer, with configurable metadata providing a unique user experience and feature set for each one. Authorization and security policies ensure that each customer's data is kept separate from that of other customers; and, from the end user's perspective, there is no indication that the application instance is being shared among multiple tenants.
The application plane—which varies a great deal depending on the nature of the product—implements the core functionality of the SaaS product.{{sfn |Golding |2024|p=28}} Key design issues include separating different tenants so they cannot view or change other tenants' data or resources.{{sfn |Golding |2024|pp=36-37}} Except for the simplest SaaS applications, some [[microservices]] and other resources are allocated on a per-tenant basis, rather than shared between all tenants.{{sfn |Golding |2024|p=37}} Routing functionality is necessary to direct tenant requests to the appropriate services.{{sfn |Golding |2024|p=38}}


[[File:Example SaaS deployment architecture.png|thumb|Example SaaS deployment architecture that offers complete siloing on a premium tier and mixed [[microservice]] deployment to other tenants{{sfn |Golding |2024|p=76}} |upright=2|center]]
At the fourth and final level of maturity, the vendor hosts multiple customers on a load-balanced farm of identical instances, with each customer's data kept separate, and with configurable metadata providing a unique user experience and feature set for each customer. A SaaS IV system is scalable to an arbitrarily large number of customers, because the number of servers and instances on the back-end can be increased or decreased as necessary to match demand, without requiring additional re-architecting of the application, and changes or fixes can be rolled out to thousands of tenants as easily as a single tenant.
Some SaaS products do not share any resources between tenants—called siloing. Although this negates many of the efficiency benefits of SaaS, it makes it easier to migrate [[legacy software]] to SaaS{{sfn |Golding |2024|p=55}} and is sometimes offered as a premium offering at a higher price.{{sfn |Golding |2024|pp=55, 74-75}} Pooling all resources might make it possible to achieve higher efficiency,{{sfn |Golding |2024|p=69}} but an outage affects all customers so availability must be prioritized to a greater extent.{{sfn |Golding |2024|p=70}} Many systems use a combination of both approaches, pooling some resources and siloing others.{{sfn |Golding |2024|pp=75-76}} Other companies group multiple tenants into pods and share resources between them.{{sfn |Golding |2024|p=78}}


==Legal issues==
Because of the development and operational difficulty associated with both the more mature levels of architectural style as well as the mission-critical auxiliary components required of all SaaS applications, certain vendors have focused on creating tools to aid in SaaS development and operations. These vendors provide other [[Independent software vendor|ISVs]] commodity components that aid in the ability to convert an existing web/web service or wap-based products into a SaaS application as well as tools that reduce the amount of time and effort required to create a SaaS application from scratch.
In the United States, constitutional [[search warrant]] laws do not protect all forms of SaaS dynamically stored data. The result is that governments may be able to request data from SaaS providers without the owner's consent.<ref>{{cite web |last=Arthur |first=Charles |url=https://www.theguardian.com/technology/blog/2010/dec/14/chrome-os-richard-stallman-warning |title=Google's ChromeOS means losing control of the data, warns GNU founder Richard Stallman |work=The Guardian |place=[[United Kingdom|UK]] |date=2010-12-14 |access-date=2012-02-16 |archive-date=2014-02-28 |archive-url=https://web.archive.org/web/20140228133145/http://www.theguardian.com/technology/blog/2010/dec/14/chrome-os-richard-stallman-warning |url-status=live }}</ref><ref>{{cite web |title=Why Richard Stallman Takes No Shine to Chrome |url=http://www.technewsworld.com/story/Why-Richard-Stallman-Takes-No-Shine-to-Chrome-71469.html |work=Linux Insider |last=Adhikari |first=Richard |date=2010-12-15 |access-date=2015-03-24 |archive-date=2021-01-23 |archive-url=https://web.archive.org/web/20210123151909/http://www.technewsworld.com/story/Why-Richard-Stallman-Takes-No-Shine-to-Chrome-71469.html }}</ref>


Certain [[open-source license]]s such as [[GNU_General_Public_License|GPL-2.0]] do not explicitly grant rights permitting distribution as a SaaS product in Germany.{{sfn|Ballhausen|2014|p=61}}
These tools can reduce time to market and engineering cost and effort involved in converting a traditional [[on-premise software]] product into a SaaS solution or in building and deploying a new solution as a SaaS solution. Examples of enablement components range from pieces of software that provide functionality such as subscription management, to full-fledged [[SaaS platform]] products that provide a technology stack and application container for deploying a SaaS application.<ref>{{cite web| title=Repealing the SaaS Tax| url=http://itmanagement.earthweb.com/article.php/3663266| accessdate=2007-03-07 | year=2007| month=March| first=Sinclair| last=Schuller}}</ref>


==References==
=== Factors Limiting SaaS adoption ===


{{Reflist |32em}}
SaaS was originally considered a potential security and operational risk. Many businesses wish to keep their information technology operations under internal control. However, there is a counter-argument that the professionals operating SaaS applications may have much better security and redundancy tools available to them, and therefore the level of service may be superior in many cases. SaaS applications may pose some difficulty for businesses that need extensive customization. SaaS vendors have made progress however, with both customization and publication of their programming interfaces. In addition, the availability of open source applications, inexpensive hardware and low cost bandwidth combine to offer compelling economic reasons for businesses to operate their own software applications, particularly as open source solutions have become higher quality and easier to install.
==Sources==
{{refbegin|indent=yes}}
*{{cite journal |last1=Ballhausen |first1=Miriam |title=OpenSaaS: Using Free and Open Source Software as Software-as-a-Service |journal=International Free and Open Source Software Law Review |date=2014 |volume=6 |pages=61-68 |url=https://www.jolts.world/index.php/jolts/article/view/103 |issn=2666-8106}}
*{{cite book |last1=Bhandari |first1=Guru Prasad |last2=Gupta |first2=Ratneshwer |title=Advancing Consumer-Centric Fog Computing Architectures |date=2019 |publisher=IGI Global |isbn=978-1-5225-7149-0 |pages=1–37 |language=en |chapter=An Overview of Cloud and Edge Computing Architecture and Its Current Issues and Challenges}}
*{{cite book |last1=Dempsey |first1=David |last2=Kelliher |first2=Felicity |title=Industry Trends in Cloud Computing: Alternative Business-to-Business Revenue Models |date=2018 |publisher=Springer International Publishing |isbn=978-3-319-87693-1 |language=en}}
*{{cite book |last1=Garbis |first1=Jason |last2=Chapman |first2=Jerry W. |title=Zero Trust Security: An Enterprise Guide |date=2021 |publisher=Apress |isbn=978-1-4842-6703-5 |language=en}}
*{{cite book |last1=Golding |first1=Tod |title=Building Multi-Tenant SaaS Architectures |date=2024 |publisher=O'Reilly Media |isbn=978-1-0981-4061-8 |language=en}}
*{{cite book |last1=Ibrahim |first1=Ahmed Mamdouh Abdelfatah |last2=Abdullah |first2=Norris Syed |last3=Bahari |first3=Mahadi |title=Software as a Service Challenges: A Systematic Literature Review |date=2023 |publisher=Springer International Publishing |isbn=978-3-031-18344-7 |pages=257–272 |ref={{sfnref|Ibrahim et al.|2023}} |language=en}}
*{{cite book |last1=Kinnunen |first1=Juha |title=ERP as Software-as-a-Service: Factors Depicting Large Enterprises Cloud Adoption |date=2022 |publisher=Springer International Publishing |isbn=978-3-030-99191-3 |pages=123–142 |language=en}}
* {{cite book |last1=Lynn |first1=Theo |last2=Mooney |first2=John G. |last3=Rosati |first3=Pierangelo |last4=Fox |first4=Grace |title=Measuring the Business Value of Cloud Computing |date=2020 |publisher=Springer Nature |isbn=978-3-030-43198-3 |language=en}}
**{{cite book |last1=Tallon |first1=Paul P. |last2=Mooney |first2=John G. |last3=Duddek |first3=Marvin |title=Measuring the Business Value of Cloud Computing |date=2020 |publisher=Springer International Publishing |isbn=978-3-030-43198-3 |pages=1–17 |language=en |chapter=Measuring the Business Value of IT|ref={{sfnref|Tallon et al.|2020}}}}
**{{cite book |last1=Rosati |first1=Pierangelo |last2=Lynn |first2=Theo |title=Measuring the Business Value of Cloud Computing |date=2020 |publisher=Springer International Publishing |isbn=978-3-030-43198-3 |pages=19–37 |language=en |chapter=Measuring the Business Value of Infrastructure Migration to the Cloud}}
**{{cite book |last1=Clohessy |first1=Trevor |last2=Acton |first2=Thomas |last3=Morgan |first3=Lorraine |title=Measuring the Business Value of Cloud Computing |date=2020 |publisher=Springer International Publishing |isbn=978-3-030-43198-3 |pages=39–55 |ref={{sfnref|Clohessy et al.|2020}} |language=en |chapter=The SaaS Payoff: Measuring the Business Value of Provisioning Software-as-a-Service Technologies}}
*{{cite book |title=Cloud Computing: Concepts and Technologies |page=105 |isbn=9781000337952 |last1=Manvi |first1=Sunilkumar |last2=Shyam |first2=Gopal |date=2021 |publisher=CRC Press }}
*{{cite book |last1=Watt |first1=Andy |title=Building Modern SaaS Applications with C# And . NET: Build, Deploy, and Maintain Professional SaaS Applications |date=2023 |publisher=Packt |isbn=978-1-80461-087-9 |language=en}}
*{{cite journal |last1=Younas |first1=Muhammad |last2=Jawawi |first2=Dayang N. A. |last3=Ghani |first3=Imran |last4=Fries |first4=Terrence |last5=Kazmi |first5=Rafaqut |title=Agile development in the cloud computing environment: A systematic review |journal=Information and Software Technology |date=2018 |volume=103 |pages=142–158 |doi=10.1016/j.infsof.2018.06.014 |url=https://www.sciencedirect.com/science/article/abs/pii/S0950584918301319 |ref={{sfnref|Younas et al.|2018}} |issn=0950-5849}}
{{refend}}
==Further reading==
*{{cite book |last1=Fox |first1=Armando |last2=Patterson |first2=David A. |title=Engineering Software As a Service: An Agile Approach Using Cloud Computing |date=2020 |publisher=Pogo Press |isbn=978-1-7352338-0-2 |language=en}}
{{Software distribution}}
{{Cloud computing}}


{{DEFAULTSORT:Software As A Service}}
===SaaS Sales Channels===
[[Category:As a service]]

[[Category:Cloud applications]]
With products below the $100 range and it's focus on the mid market, direct selling can become an expensive undertaking. SaaS companies are seeking for alternatives by selling through VARs (Value Added Resellers) and similar alliance partners. But due to the fact that SaaS is not only a different delivery mechanism but a different business model and different technology as well, selling through channels has its own challenges. A recent [http://channel-excellence.blogspot.com/2007/04/new-channels-for-saas.html white paper] published by the [[SIIA]] (Software & Information Industry Association) explains such differences to traditional software in more details.
[[Category:Software delivery methods]]



== See also ==
* [[Application service provider]]
* [[SaaS platform]]
* [[Saasu]]
* [[Software appliance]]
* [[Utility computing]]
* [[Vendor-independent solutions provider]]
* [[Supply Chain]]
* [[Mobile enterprise]]
* [[Secure Virtual Office]]

== External links ==
* [http://www.tanooma.com Independent SaaS Directory]
* [http://www.saas-portal.com saas-portal.com competence community]
* [http://www.saassdlc.com saas sdlc open operations framework]
* [http://msdn2.microsoft.com/en-us/architecture/aa699384.aspx MSDN Architecture Center]

==References==
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See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how
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{{FootnotesSmall|resize=100%}}
[[Category:Business models]]
[[Category:Software distribution]]
[[Category:Software distribution]]
[[Category:Services management and marketing]]
[[Category:Software industry]]
[[Category:Revenue models]]
[[Category:Service-oriented (business computing)|Software as a Service (SaaS)]]

[[de:Software as a Service]]
[[es:Software como Servicio]]
[[fr:SaaS]]
[[ko:서비스로서의 소프트웨어]]
[[he:שירות תוכנה]]
[[mn:SaaS]]
[[nl:Software as a Service]]
[[ja:Software as a Service]]
[[ru:SaaS]]

Latest revision as of 01:42, 1 January 2025

"SaaS" redirects here. Not to be confused with Security as a service.

Software as a service (SaaS /sæs/[1]) is a cloud computing service model where the provider offers use of application software to a client and manages all needed physical and software resources.[2] SaaS is usually accessed via a web application. Unlike other software delivery models, it separates "the possession and ownership of software from its use".[3] SaaS use began around 2000, and by 2023 was the main form of software application deployment.

Unlike most self-hosted software products, only one version of the software exists[citation needed] and only one operating system and configuration is supported. SaaS products typically run on rented infrastructure as a service (IaaS) or platform as a service (PaaS) systems including hardware and sometimes operating systems and middleware, to accommodate rapid increases in usage while providing instant and continuous availability to customers. SaaS customers have the abstraction of limitless computing resources, while economy of scale drives down the cost. SaaS architectures are typically multi-tenant; usually they share resources between clients for efficiency, but sometimes they offer a siloed environment for an additional fee. Common SaaS revenue models include freemium, subscription, and usage-based fees. Unlike traditional software, it is rarely possible to buy a perpetual license for a certain version of the software.

There are no specific software development practices that distinguish SaaS from other application development, although there is often a focus on frequent testing and releases.

Cloud computing

Main article: Cloud computing
Comparison of on-premise, IaaS, PaaS, and SaaS

Infrastructure as a service (IaaS) is the most basic form of cloud computing, where infrastructure resources—such as physical computers—are not owned by the user but instead leased from a cloud provider. As a result, infrastructure resources can be increased rapidly, instead of waiting weeks for computers to ship and set up. IaaS requires time and expertise to make use of the infrastructure in the form of operating systems and applications.[4] Platform as a service (PaaS) includes the operating system and middleware, but not the applications.[5][6] SaaS providers typically use PaaS or IaaS services to run their applications.[5]

Without IaaS, it would be extremely difficult to make an SaaS product scalable for a variable number of users while providing the instant and continual availability that customers expect.[7] Most end users consume only the SaaS product and do not have to worry about the technical complexity of the physical hardware and operating system.[8] Because cloud resources can be accessed without any human interactions, SaaS customers are provided with the abstraction of limitless computing resources, while economy of scale drives down the cost.[9] Another key feature of cloud computing is that software updates can be rolled out and made available to all customers nearly instantaneously.[10] In 2019, SaaS was estimated to make up the plurality, 43 percent, of the cloud computing market while IaaS and PaaS combined account for approximately 25 percent.[11]

History

In the 1960s, multitasking was invented, enabling mainframe computers to serve multiple users simultaneously. Over the next decade, timesharing became the main business model for computing, and cluster computing enabled multiple computers to work together.[9] Cloud computing emerged in the late 1990s with companies like Amazon (1994), Salesforce (1999), and Concur (1993) offering Internet-based applications on a pay-per-use basis. All of these focused on a single product to seize a high market share.[12] Beginning with Gmail in 2004, email services were some of the first SaaS products to be mass-marketed to consumers.[13] The market for SaaS grew rapidly throughout the early twenty-first century.[14][11] Initially viewed as a technological innovation, SaaS has come to be perceived more as a business model.[15] By 2023, SaaS had become the primary method that companies deliver applications.[16]

Popular consumer SaaS products include all social media websites, email services like Gmail and its associated Google Docs Editors,[17] Skype, Dropbox,[18] and entertainment products like Netflix and Spotify.[19] Enterprise SaaS products include Salesforce's customer relationship management (CRM) software, SAP Cloud Platform, and Oracle Cloud Enterprise Resource Planning.[18]

Revenue models

Some SaaS providers offer free services to consumers that are funded by means such as advertising, affiliate marketing, or selling consumer data.[20] One of the most popular models for Internet start-ups and mobile apps is freemium, where the company charges for continued use or a higher level of service. Even if the user never upgrades to the paid version, it helps the company capture a higher market share and displace customers from a rival.[21] However, the company's hosting cost increases with the number of users, regardless of whether it is successful at enticing them to use the paid version.[22] Another common model is where the free version only provides demonstration (crippleware). Online marketplaces may charge a fee on transactions to cover the SaaS provider costs.[20] It used to be more common for SaaS products to be offered for a one-time cost, but this model is declining in popularity.[20] A few[20] SaaS products have open source code, called open SaaS. This model can provide advantages such as reduced deployment cost, less vendor commitment, and more portable applications.[23]

The most common SaaS revenue models involve subscription and pay for usage.[24] For customers, the advantages include reduced upfront cost, increased flexibility, and lower overall cost compared to traditional software with perpetual software licenses.[25] In some cases, the steep one-time cost demanded by sellers of traditional software were out of the reach of smaller businesses, but pay-per-use SaaS models makes the software affordable.[3] Usage may be charged based on the number of users, transactions, amount of storage spaced used, or other metrics.[26] Many buyers prefer pay-per-usage because they believe that they are relatively light users of the software, and the seller benefits by reaching occasional users who would otherwise not buy the software.[26] However, it can cause revenue uncertainty for the seller and increases the overhead for billing.[27]

The subscription model of SaaS offers a continuing and renewable revenue stream to the provider, although vulnerable to cancellation.[3] If a significant number are cancelled, the viability of the business can be placed in jeopardy.[3] The ease of canceling a subscription and switching to a competitor leave customers with the leverage to get concessions from the seller.[28] While recurring revenues can help the business and attract investors, the need for customer service skills in convincing the customer to renew their subscription is a challenge for providers switching to subscription from other revenue models.[29]

Adoption

SaaS products are typically accessed via a web browser as a publicly available web application.[30][16] This means that customers can access the application anywhere from any device without needing to install or update it.[16][31] SaaS providers often try to minimize the difficulty of signing up for the product.[32] Many capitalize on the service-oriented structure to respond to customer feedback and evolve their product quickly to meet demands. This can enable customers to believe in the continued improvement of the product and help the SaaS provider get customers from an established traditional software company that likely can offer a deeper feature set.[33][34]

Although on-premises software is often less secure than SaaS alternatives,[35] security and privacy are among the main reasons cited by companies that do not adopt SaaS products.[36] SaaS companies have to protect their publicly available offerings from abuse, including denial-of-service attacks and hacking.[37] They often use technologies such as access control, authentication, and encryption to protect data confidentiality.[36] Nevertheless, not all companies trust SaaS providers to keep sensitive data secured.[36] The vendor is responsible for software updates, including security patches, and for protecting the customers' data.[31] SaaS systems inherently have a greater latency than software run on-premises due to the time for network packets to be delivered to the cloud facility. This can be prohibitive for some uses, such as time-sensitive industrial processes or warehousing.[38]

The rise of SaaS products is one factor leading many companies switched from budgeting for IT as a capital expenditure to an operating expenditure.[39] The process of migration to SaaS and supporting it can also be a significant cost that must be accounted for.[40][29]

Development

A SaaS architecture. All customers are running the same version of the software on the same platform.[41]

A challenge for SaaS providers is that demand is not known in advance. Their system must have enough slack to be able to handle all users without turning any away, but without paying for too many resources that will be unnecessary. If resources are static, they are guaranteed to be wasted during non-peak time.[42] Sometimes cheaper off-peak rates are offered to balance the load and reduce waste.[43] The expectation for continuous service is so high that outages in SaaS software are often reported in the news.[44]

There are not specific software development practices that differentiate SaaS from other application development.[45] SaaS products are often released early and often to take advantage of the flexibility of the SaaS delivery model.[46] Agile software development is commonly used to support this release schedule.[47] Many SaaS developers use test-driven development, or otherwise emphasize frequent software testing, because of the need to ensure availability of their service and rapid deployment.[48] Domain-driven design, in which business goals drive development, is popular because SaaS products must sell themselves to the customer by being useful.[49] SaaS developers do not know in advance which devices customers will try to access the product from—such as a desktop computer, tablet, or smartphone—and supporting a wide range of devices is often an important concern for the front-end development team.[50] Progressive web applications allow some functionality to be available even if the device is offline.[51]

SaaS applications predominantly offer integration protocols and application programming interfaces (APIs) that operate over a wide area network.[52]

Architecture

SaaS architecture varies significantly from product to product.[53] Nevertheless, most SaaS providers offer a multi-tenant architecture.[30] With this model, a single version of the application, with a single configuration (hardware, network, operating system), is used for all customers ("tenants").[54] This means that the company does not need to support multiple versions and configurations.[16] The architectural shift from each customer running their own version of the software on their own hardware affects many aspects of the application's design and security features.[54] In a multi-tenant architecture, many resources can be used by different tenants or shared between multiple tenants.[55]

Application and control planes of a SaaS product

The structure of a typical SaaS application can be separated into application and control planes.[56] SaaS products differ in how these planes are separated, which might be closely integrated or loosely coupled in an event- or message-driven model.[57] The control plane is in charge of directing the system and covers functionality such as tenant onboarding, billing, and metrics, as well as the system used by the SaaS provider to configure, manage, and operate the service.[56] Many SaaS products are offered at different levels of service for different prices, called tiering. This can also affect the architecture for both planes, although it is commonly placed in the control plane.[58] Unlike the application plane, the services in the control plane are not designed for multitenancy.[59]

An example architecture where some services are shared, while others are allocated on a per-tenant basis[60]

The application plane—which varies a great deal depending on the nature of the product—implements the core functionality of the SaaS product.[59] Key design issues include separating different tenants so they cannot view or change other tenants' data or resources.[61] Except for the simplest SaaS applications, some microservices and other resources are allocated on a per-tenant basis, rather than shared between all tenants.[62] Routing functionality is necessary to direct tenant requests to the appropriate services.[60]

Example SaaS deployment architecture that offers complete siloing on a premium tier and mixed microservice deployment to other tenants[63]

Some SaaS products do not share any resources between tenants—called siloing. Although this negates many of the efficiency benefits of SaaS, it makes it easier to migrate legacy software to SaaS[64] and is sometimes offered as a premium offering at a higher price.[65] Pooling all resources might make it possible to achieve higher efficiency,[66] but an outage affects all customers so availability must be prioritized to a greater extent.[67] Many systems use a combination of both approaches, pooling some resources and siloing others.[68] Other companies group multiple tenants into pods and share resources between them.[69]

In the United States, constitutional search warrant laws do not protect all forms of SaaS dynamically stored data. The result is that governments may be able to request data from SaaS providers without the owner's consent.[70][71]

Certain open-source licenses such as GPL-2.0 do not explicitly grant rights permitting distribution as a SaaS product in Germany.[72]

References

  1. ^ Panker, Jon; Lewis, Mark; Fahey, Evan; Vasquez, Melvin Jafet (August 2007). "How do you pronounce IT?". TechTarget. Archived from the original on 28 November 2016. Retrieved 24 May 2012.
  2. ^ Golding 2024, p. 14.
  3. ^ a b c d Dempsey & Kelliher 2018, p. 2.
  4. ^ Rosati & Lynn 2020, p. 22.
  5. ^ a b Rosati & Lynn 2020, p. 23.
  6. ^ Ibrahim et al. 2023, p. 258.
  7. ^ Dempsey & Kelliher 2018, p. 17.
  8. ^ Dempsey & Kelliher 2018, pp. 17–18.
  9. ^ a b Dempsey & Kelliher 2018, p. 19.
  10. ^ Dempsey & Kelliher 2018, p. 33.
  11. ^ a b Rosati & Lynn 2020, p. 20.
  12. ^ Dempsey & Kelliher 2018, pp. 23, 31.
  13. ^ Watt 2023, p. 8.
  14. ^ Dempsey & Kelliher 2018, pp. 24, 32.
  15. ^ Dempsey & Kelliher 2018, p. 35.
  16. ^ a b c d Watt 2023, p. 4.
  17. ^ Watt 2023, pp. 4, 8.
  18. ^ a b Clohessy et al. 2020, p. 40.
  19. ^ Watt 2023, p. 9.
  20. ^ a b c d Dempsey & Kelliher 2018, p. 48.
  21. ^ Dempsey & Kelliher 2018, pp. 61–63.
  22. ^ Dempsey & Kelliher 2018, pp. 63–64.
  23. ^ Bhandari & Gupta 2019, p. 21.
  24. ^ Dempsey & Kelliher 2018, pp. 48, 57.
  25. ^ Clohessy et al. 2020, pp. 40–41.
  26. ^ a b Dempsey & Kelliher 2018, p. 57.
  27. ^ Dempsey & Kelliher 2018, pp. 57–58.
  28. ^ Dempsey & Kelliher 2018, p. 11.
  29. ^ a b Dempsey & Kelliher 2018, p. 66.
  30. ^ a b Garbis & Chapman 2021, p. 185.
  31. ^ a b Kinnunen 2022, pp. 123–124.
  32. ^ Golding 2024, p. 18.
  33. ^ Golding 2024, p. 20.
  34. ^ Watt 2023, p. 15.
  35. ^ Watt 2023, pp. 6, 16.
  36. ^ a b c Ibrahim et al. 2023, pp. 264, 266, 268.
  37. ^ Garbis & Chapman 2021, p. 186.
  38. ^ Kinnunen 2022, pp. 137, 139.
  39. ^ Tallon et al. 2020, p. 2.
  40. ^ Kinnunen 2022, p. 124.
  41. ^ Golding 2024, p. 25.
  42. ^ Dempsey & Kelliher 2018, p. 36.
  43. ^ Dempsey & Kelliher 2018, p. 37.
  44. ^ Dempsey & Kelliher 2018, p. 39.
  45. ^ Watt 2023, p. 11.
  46. ^ Watt 2023, p. 16.
  47. ^ Younas et al. 2018, p. 142.
  48. ^ Watt 2023, pp. 11–12, 16.
  49. ^ Watt 2023, p. 12.
  50. ^ Watt 2023, pp. 13–14.
  51. ^ Watt 2023, p. 13.
  52. ^ Manvi & Shyam 2021, p. 105.
  53. ^ Golding 2024, p. 47.
  54. ^ a b Golding 2024, pp. 25–26.
  55. ^ Golding 2024, p. 26.
  56. ^ a b Golding 2024, p. 27.
  57. ^ Golding 2024, p. 44.
  58. ^ Golding 2024, p. 40.
  59. ^ a b Golding 2024, p. 28.
  60. ^ a b Golding 2024, p. 38.
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  62. ^ Golding 2024, p. 37.
  63. ^ Golding 2024, p. 76.
  64. ^ Golding 2024, p. 55.
  65. ^ Golding 2024, pp. 55, 74–75.
  66. ^ Golding 2024, p. 69.
  67. ^ Golding 2024, p. 70.
  68. ^ Golding 2024, pp. 75–76.
  69. ^ Golding 2024, p. 78.
  70. ^ Arthur, Charles (2010-12-14). "Google's ChromeOS means losing control of the data, warns GNU founder Richard Stallman". The Guardian. UK. Archived from the original on 2014-02-28. Retrieved 2012-02-16.
  71. ^ Adhikari, Richard (2010-12-15). "Why Richard Stallman Takes No Shine to Chrome". Linux Insider. Archived from the original on 2021-01-23. Retrieved 2015-03-24.
  72. ^ Ballhausen 2014, p. 61.

Sources

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  • Garbis, Jason; Chapman, Jerry W. (2021). Zero Trust Security: An Enterprise Guide. Apress. ISBN 978-1-4842-6703-5.
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  • Ibrahim, Ahmed Mamdouh Abdelfatah; Abdullah, Norris Syed; Bahari, Mahadi (2023). Software as a Service Challenges: A Systematic Literature Review. Springer International Publishing. pp. 257–272. ISBN 978-3-031-18344-7.
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    • Rosati, Pierangelo; Lynn, Theo (2020). "Measuring the Business Value of Infrastructure Migration to the Cloud". Measuring the Business Value of Cloud Computing. Springer International Publishing. pp. 19–37. ISBN 978-3-030-43198-3.
    • Clohessy, Trevor; Acton, Thomas; Morgan, Lorraine (2020). "The SaaS Payoff: Measuring the Business Value of Provisioning Software-as-a-Service Technologies". Measuring the Business Value of Cloud Computing. Springer International Publishing. pp. 39–55. ISBN 978-3-030-43198-3.
  • Manvi, Sunilkumar; Shyam, Gopal (2021). Cloud Computing: Concepts and Technologies. CRC Press. p. 105. ISBN 9781000337952.
  • Watt, Andy (2023). Building Modern SaaS Applications with C# And . NET: Build, Deploy, and Maintain Professional SaaS Applications. Packt. ISBN 978-1-80461-087-9.
  • Younas, Muhammad; Jawawi, Dayang N. A.; Ghani, Imran; Fries, Terrence; Kazmi, Rafaqut (2018). "Agile development in the cloud computing environment: A systematic review". Information and Software Technology. 103: 142–158. doi:10.1016/j.infsof.2018.06.014. ISSN 0950-5849.

Further reading

  • Fox, Armando; Patterson, David A. (2020). Engineering Software As a Service: An Agile Approach Using Cloud Computing. Pogo Press. ISBN 978-1-7352338-0-2.
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