What is Software as a Service (SaaS)

Cloud computing has been one of the most disruptive technologies, which has changed the way IT is consumed by enterprises, both small and large. The ability to subscribe to “as-a-service” consumption model, while converting capital expenditure to operational expenditure, has been a key driver for Cloud adoption. Rapid provisioning and deprovisioning of services, elastic scaling of infrastructure resources and self-service ability for users are some of the key characteristics and benefits offered by Cloud. Infrastructure as a Service (IaaS) provides the basic building block, with Platform as a Service (PaaS) providing a layer of abstraction on top of IaaS and similarly Software as a Service (SaaS) providing a layer of abstraction on top of PaaS. Moving up the layers reduces complexity and enables users to tap into a much larger spectrum of benefits that Cloud computing has to offer. While Cloud opens the door for “as-a-service” consumption model, there are many additional benefits that can be realized by enterprises beyond the typical IaaS, PaaS and SaaS. A number of these benefits can be realized by leveraging Cloud in different scenarios and use cases. For example, an enterprise may continue to pursue a traditional non-Cloud based infrastructure deployment strategy, however, it could use a public Cloud for storage elasticity. Such use cases exemplify many atypical benefits that Cloud can provide, which often got overlooked. This paper will present a number of such cloud deployment use cases that go beyond the typical IaaS usage of cloud. A hierarchical architectural model of cloud solution pattern is proposed to describe both the business requirements and technical considerations of these use cases. These cloud architectural patterns are further elaborated through real-life case studies and examples.