Principles, Methodology and Tools for Engineering Cloud Computing Systems - Advanced Design Approaches to Emerging Software Systems - page 252

derstanding in the community has been established
that these are the main areas of Cloud Computing
services/product that are offered on the market
(also see Figure 1):

cess to the software which has been created
and is maintained by the cloud provider.

The approach described here represents a
lifecycle-based methodology that is illustrated
with relevant examples from significant and
most recent literature and research. A coherent
methodology, which could support companies to
embrace the Cloud, is still lacking. That has held
back progress both on provider and on consumer
side. The presented innovative approach, once ap-
plied, has the potential to create transparency for
the promising IT paradigm of Cloud Computing.
To strengthen the proposed approach we apply
principles, present a methodology and showcase
tools for engineering Cloud Computing systems.
While understanding the basic technical and
business features of this new computing paradigm
is essential, one has to see the complete picture
and understand the implications for the provision
of complex Cloud services including components
such as networks, machines, infrastructures and
software. Therefore, management of the com-
plexity of consuming Cloud services needs to
be understood as a supply chain. As an explicit
definition for the Cloud Supply Chain (C-SC),

• At its most basic level Infrastructure-as-a-

Service (IaaS) delivers resources like pre-
packaged sets of e.g. CPU and RAM.
Virtualized system images can be uploaded
to a cloud provider who provides place-
ment and execution of these images on
physical hardware within their data centers
or within a federated cloud infrastructure.

• Platform-as-a-Service (PaaS) delivers vir-

tualization and scaling of abstracted soft-
ware packages above the level of the op-
erating system. Packaged applications are
usually uploaded to a cloud platform, or
directly developed on the cloud platform
itself.

• Software-as-a-Service (SaaS) is perhaps

the most common of the 'as-a-Service'
terms, and describes fully managed appli-
cations delivered as a service. Customers
do not need to upload server images or
software packages. Instead, they rent ac-

Figure 1. Cloud Supply Chain