SaaS – Software as a Service

Software-as-a-Service provides complete applications to a cloud’s end user. It is mainly accessed through a web portal and service oriented architectures based on web service technologies. Credit card or bank account details must be provided to enable the fees for the use of the services to be billed.
The services on the application layer can be seen as an extension of the ASP (application service provider) model, in which an application is run, maintained, and supported by a service vendor. The main differences between the services on the application layer and the classic ASP model are the encapsulation of the application as a service, the dynamic procurement, and billing by units of consumption (pay as you go). However, both models pursue the goal of focusing on core competencies by outsourcing applications.

Figure 1: Software-as-a-Service (SaaS) Stack