Page 71 - Cloud Essentials

A SaaS application is by definition multitenant. SaaS apps are built with

multiple users in mind, and they are optimized for remote use.
Customization of the application either is a client-configurable option or
is done through add-ons, plug-ins, or web services. None of these involves
any change in the core application software. As for security, SaaS providers
must ensure that one customer cannot access information from another
customer. Note that there is already an obligation to make sure two users of
the same customer can see each other’s information only if authorized
properly.

Platform as a Service (PaaS)
PaaS is of interest to software developers; it enables the creation of a rich
universe of application components and services that can be used by other

applications, all delivered over a network. Table 3-1 lists scopes of PaaS
along with examples.

TABLE 3-1 PaaS Scopes and Examples

Traditionally, creating, testing, and maintaining software applications
was costly and complex. This is because investments in hardware, software,
licensing, and networking infrastructure were required. To make matters
worse, after a specific application development project, the investment in

computing resources might not be used to its full capacity, therefore
representing waste.
Now, how does PaaS technically work? Most of these platforms are
accessed through web services. A web service is an application
programming interface (API) that looks like a web server and can be
accessed through URLs. These URLs encode the operations to be
performed. The parameters for these calls are then also part of the URL, or

they are transmitted using the HTTP POST operation. Results are

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