In a nutshell, cloud computing can be described as a particular type of computing service that uses shared resources in order to process data on-demand whereby shared resources refers to any kind of hardware or software components (e.g. networks, servers or other infrastructure, storage, applications and services) that are released on-demand to users for processing data. The term sharable defines computing resources where many users are utilizing the same physical infrastructure for processing data. The computing resource can be defined as sharable if the pool of resources used by the provider can be extended or reduced at any time, depending on the user requirements. Thus, data centres or single components within one data centre could possibly be added or removed if the total amount of computing or storage capacity needs an update. The term elastic pool can be described as workload changes by provisioning and de-provisioning resources in an automatic manner, such that at each point in time the available resources match the current demand as closely as possible”35. There are at present three main types of cloud service models which a provider can offer:  Infrastructure as a Service (IaaS): A cloud service category in which the cloud capabilities type provided to the customer is an infrastructure. It includes the virtual delivery of computing resources in the form of hardware, networking and storage services. IaaS powers servers, storage, networks and operating systems. It provides enterprise infrastructure in which a business can store its data and run the applications needed for its daily operation.  Platform as a Service (PaaS): A cloud service category in which the cloud capabilities type provided to the customer is a platform. It includes online computing platforms that allow companies to run existing applications or to develop and test new ones.  Software as a service (SaaS): A cloud service category in which the cloud capabilities type provided to the customer is an application or software deployed over the Internet. This type of cloud services removes the need for the end user to buy, install and manage software, and has the advantage of making the software accessible from anywhere with an internet connection. Nikolas Roman Herbst, Samuel Kounev, Ralf Reussner, Karlsruhe Institute of Technology, “Elasticity in Cloud Computing: What It Is, and What It Is Not”, available at: https://sdqweb.ipd.kit.edu/publications/pdfs/HeKoRe2013-ICAC-Elasticity.pdf. See also pages 2-5 of COM(2012) 529. 35 33