Terms often associated with the Software as a Service pattern include:
Cloud Computing is not the same as SaaS; rather, it is a specialized pattern of virtualization. Utility and Cloud Computing refer to treating computing resources as virtualized, metered services, similar from a consumer’s perspective to how we consume other utilities (such as water, gas, electricity, and pay-per-view cable).
On-demand applications provide access to computing resources on an ad hoc basis when the functionality is required. Using the http://createpdf.adobe.com service to create a single PDF document online rather than having to download and install a version of Acrobat is a good example.
This pattern relates to software that spans Internet-connected devices and builds on the growing pervasiveness of the online experience. It touches on various aspects of the SaaS pattern; in particular, the concepts of distributed computing of tasks via network connections.
Some people consider SaaS a specialization of the MVC pattern that distributes the Model, View, and Controller (or parts thereof) over multiple resources located on the Internet. It is strongly related to SaaS, and most SaaS providers follow the MVC pattern when implementing SaaS.
Consider a software vendor that wishes to develop spam removal ...