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Platform as a Service (PaaS)
As shown in the model, PaaS builds on infrastructure resources and is often
referred to as ‘middleware’. This can be understood to contain all of the
required runtime environments, applications, tools, databases, web services
and so on. In other words, components that provide a standardised basis for
the applications to be deployed, and which can also be put together in a
modular way. These offerings give Cloud customers the ability to create or
implement individual end to end business solutions.
Examples of PaaS include Google's App Engine, IBM's Rational Portfolio and
Microsoft Azure.
Software as a Service (SaaS)
The application level is currently the most frequently offered and discussed
Cloud service. The "Software as a Service" distribution model has been
around for a long time on the IT market and was added to the service
platform model at a later stage. However, it only fulfills its claim to be a
Cloud computing service if the offering is massively scalable, multi‐tenant
capable and elastically flexible, as well as supporting other Cloud computing
attributes . Customers use the software on a pay‐as‐you‐go basis and do not
need to concern themselves with the underlying basic technologies (such as
the infrastructure or platform). All components residing below it are part of
the package price and typically even transparent for users.
Examples of SaaS include Google Gmail, IBMs LotusLive, Microsoft Office
365,
CRM by Salesforce.com, Netsuite, or SPScommerce.net.
Cloud Management as a Service (MaaS)
Cloud Management as a Service provides the management framework for a
private Cloud, or a Cloud Service. The customer themselves provision new
resources (storage) or service and users.
A company wants to implement a simple web application that gives its
customers the ability to perform product queries. The first step in the
project is to forecast the usage and derive the IT resource requirements
from this assumption. The next step is to commission a programmer, design
the websites and the database structure. The tool is then provided to the
company's customers, and this is where a decision is made choosing not to
operate the required hardware (infrastructure) in‐house, but to rent the
hardware as IaaS from a Cloud service provider. For the initial phase of this
project, a server with a local database and web server functionality is
sufficient. The decision goes in favour of a server in Amazon's EC². The
