Software as a service is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. Users can access it with the help of web browsers.

SaaS is a common delivery model for many business applications, including office and messaging software, management software,virtualization etc. It is part of the nomenclature of cloud computing, along with infrastructure as a service(IaaS), platform as a service(PaaS), desktop as a service(DaaS).

It is associated with the application service providers (ASPs) which provides “shrink-wrap” applications to business users over the Internet. Early Internet-delivered software had features similar to on-premise applications compared to SaaS applications. Because these were originally built as single-tenant applications, their ability to share data was limited. SaaS applications are single-instance, multi-tenant architecture that provide a feature-rich experience competitive with on-premise applications. Aggregator bundles SaaS offerings from different vendors and offers them as part of a unified application platform.

The SaaS provider hosts the application and data centrally — deploying patches . They upgrade to the application transparently, delivering access to end users over the Internet. Many vendors provide API’s that developers use for creating composite applications. It contains various security mechanisms for Data security during transmission and storage.

**SAAS Architecture:**

With this model, a single version of the application, with a single configuration is used for all customers. The application is installed on multiple machines to support scalability (called horizontal scaling). In some cases, a second version of the application is set up to offer a select group of customers with access to pre-release versions of the applications for testing purposes. In this traditional model, each version of the application is based on a unique code. Although an exception , some SaaS solutions do not use multitenancy, to cost-effectively manage a large number of customers in place. Whether multitenancy is a necessary component for software-as-a-service is a topic of controversy.

There are two main varieties of SaaS:

*   Vertical SaaS
*   A Software which answers the needs of a specific industry (e.g., software for the healthcare, agriculture, real estate, finance industries)
*   Horizontal SaaS
*   The products which focus on a software category (marketing, sales, developer tools, HR) but are industry agnostic.

![](https://hackernoon.com/hn-images/0*N69lerCIIlNQvkZ9.png)

**Benefit of SAAS:**

It offers substantial opportunities for organizations of all sizes to shift the risks of software acquisition, and to move IT from a reactive cost center to being a proactive, value-producing part of the enterprise. Traditionally, deploying large-scale software systems has been a major undertaking. Deploying these systems across a large enterprise costs more. The time, staff, and budget requirements of a deployment of this magnitude represent a significant risk for an organization of any size, and often puts such software out of the reach of smaller organizations that would otherwise be able to derive from it a great deal of utility. The on-demand delivery model changes some of this. SaaS applications don’t require the deployment of a large infrastructure at the client’s location . This eliminates or drastically reduces the upfront commitment of resources.

Integration can be planned and executed with minimal effort, creating one of the shortest time-to-value intervals possible for a major IT investment. This has also made it possible for a number of SaaS vendors to offer risk-free (and often _literally_ free) “test drives” of their software for a limited period, such as 30 days. Giving customers a chance to try the software before they buy it helps eliminate much of the risk surrounding software purchase.

**How SaaS Affects IT ?**

After you’ve made the decision to pursue SaaS, the next is to prepare for the transition by assessing how the deployment will affect existing IT assets. Performing due diligence is a routine part of any successful IT infrastructure deployment project. Some areas to address in due-diligence checklist include,Data security standards : Moving critical business data “outside the walls” introduces a risk of data loss or inadvertent exposure of sensitive information. Assess your data-security needs, and ensure that the provider has measures in place to meet the standards you set. Reporting services : Because SaaS involves giving up direct control of some of your data, accurate and useful reporting is especially important. Determine what reporting services the provider offers, and whether they are compatible with your business-intelligence requirements.

**Impact on IT Roles and Responsibilities**

Adding SaaS can cause a fundamental shift in the IT department’s role as a provider of information services. In the past, the nature of software deployment has put chief information officers in the role of gatekeepers . They could exercise a veto by declaring that they would not host it in the data center. With SaaS , control of the data center does not necessarily equal control over the entire enterprise-computing environment. This can cause the gatekeepers to fear a loss of control.

**Conclusion**

Enterprises would do well to consider the flexibility and risk-management implications of adding SaaS to their portfolios of IT services. Integration and composition are critical components in your architecture strategies to incorporate SaaS successfully as a fully participating member of your service-centric IT infrastructure. We believe that the future of enterprise computing is not going to be purely on-premise. Instead, they will exist in symbiotic harmony.

References :

1.[https://en.wikipedia.org/wiki/Software\_as\_a\_service](https://en.wikipedia.org/wiki/Software_as_a_service)

2.[https://msdn.microsoft.com/en-us/library/aa905332.aspx](https://msdn.microsoft.com/en-us/library/aa905332.aspx)

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