Defining Software as a Service (SaaS)

The most complete cloud computing service model is one in which the computing hardware and software, as well as the solution itself, are provided by a vendor as a complete service offering. It is referred to as the Software as a Service (SaaS) model.

SaaS provides the complete infrastructure, software, and solution stack as the service offering. A good way to think about SaaS is that it is the cloud-based equivalent of shrink-wrapped software.

Software as a Service (SaaS) may be succinctly described as software that is deployed on a hosted service and can be accessed globally over the Internet, most often in a browser.

With the exception of the user interaction with the software, all other aspects of the service are abstracted away.

Every computer user is familiar with SaaS systems, which are either replacements or substitutes for locally installed software. Examples of SaaS software for end-users are Google Gmail and Calendar, QuickBooks online, Zoho Office Suite, and others that are equally well known.

SaaS applications come in all shapes and sizes, and include custom software such as billing and invoicing systems, Customer Relationship Management (CRM) applications, Help Desk applications, Human Resource (HR) solutions, as well as myriad online versions of familiar applications.

Many people believe that SaaS software is not customizable, and in many SaaS applications this is indeed the case. For user-centric applications such as an office suite, that is mostly true; those suites allow you to set only options or preferences.

However, many other SaaS solutions expose Application Programming Interfaces (API) to developers to allow them to create custom composite applications. These APIs may alter the security model used, the data schema, workflow characteristics, and other fundamental features of the service’s expression as experienced by the user.

Examples of an SaaS platform with an exposed API are Salesforce.com and Quicken.com. So SaaS does not necessarily mean that the software is static or monolithic.

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