Classroom Companion: Business

 
z Infrastructure as a Service (IaaS)
In this case, the client rent access to the IT infrastructure of the cloud provider 
(computers, databases, servers, communication interfaces, and network). The IaaS 
provider offers a virtual machine architecture supporting a number of simultane-
ous and functionally separated clients. Each client will then view the cloud as an 
individual computer where the client may develop and run arbitrary software, also 
including own operating systems and security protection if required. The client has 
no control over the underlying infrastructure but may have control over operating 
systems, storage, use of software libraries, and security settings.
A related concept is network virtualization where the user is not aware of the fact 
that the processing activities are distributed over several computers. This implies 
that the user perceives the system as a single computer over which the user has 
exclusive control.
 
z Platform as a Service (PaaS)
In this case, the cloud provider offers a software development environment for the 
clients. The PaaS platform may contain programming tool kits, software libraries, 
as well as operating systems, compilers, and databases. App Engine is a PaaS 
platform offered by Google for development of web applications.
 
z Software as a Service (SaaS)
In this case, users are given licenses to use application software and database func-
tions. All processing is then managed by the cloud provider. Examples of SaaS are 
access to office software, maps, Geographic Positioning System (GPS), Geographic 
Information System (GIS), human resource management, gamification, collabora-
tion, learning, and many other applications.
Grid computing is the interconnection of many heterogeneous computers to per-
form particularly large computational tasks. The grid is different from the cloud in 
the sense that the computers involved are lightly connected, and each of them per-
forms a dedicated and invariant task. The grid may then be viewed as a vast distrib-
uted supercomputer. The number of active computers in the grid involved in the 
same task at any instant is also varying since the computers are usually used by the 
grid only when they are not busy with computations initiated by the owner of the 
computer. Typically, the grid consists of computer facilities at universities and 
research institutions.
Tasks using grid computing are computationally hard problems such as study-
ing protein folding processes, simulating climate models, searching for large primes, 
and analyzing particle collisions at CERN. There are several active international 
grids.