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Top1. Introduction
In the IT domain, Cloud computing is one of the most recent paradigms, receiving more and more interest in literature (Vaquera et al., 2009; Sterling & Stark, 2009). Increasing opportunities for improving IT efficiency and performance through centralization of resources and the maturation of technologies such as SOA, virtualization, grid computing, and management automation led to the natural outcome of what has become increasingly referred to as “cloud computing” (Oracle, 2009). Basic motivations behind the technology are: (a) The need for rapidly scalable elastic computing infrastructures, (b) The increased cost of traditional IT infrastructure, (c) Increased focus on service orientation (Yousif, 2009; IBM, 2008).
Cloud computing represents outsourcing of IT (infrastructure, service, platform, business processes), and enables on-demand access to IT resources from the provider generally on a pay-for-use basis like a utility from external providers. This paradigm provides access to a shared pool of configurable resources (networks, servers, storage, applications and services) delivered over the Internet (Buyya, Broberg, & Goscinski, 2011; Sterling & Stark, 2009; Gartner, 2008a, b; Sosinsky, 2011; Raines, 2009).
The approach is inherently compatible with the service oriented philosophy, enabling standardized access to IT resources for totally heterogeneous, diverse and distributed infrastructures without knowledge of the underlying system details. Cloud benefits from SOA, since cloud computing is directly related with provisioning and consumption of IT capabilities as a service over the web. Markz and Lozano (2010) emphasises this idea by mentioning that “Cloud builds on the shoulders of SOA”. Thus, cloud logically builds on the concepts of services. Services organization and orchestration inside the cloud can be managed in a SOA (Wang, Wang, & Lee 2009). Since the modularity, reusability, standardization of interfaces, interoperability, platform independence and scalability are the core issues, cloud approach can be conceived of as complementing the SOA paradigm, providing pay-for-use model for service oriented thinking (Sosinsky, 2011). This is also highlighted by Markz and Lozano, (2010), mentioning the “double play” between cloud and SOA, cloud pulling new SOA initiatives through and SOA enabling cloud initiatives from business, IT and infrastructural perspectives.
Representing the virtualization of resources, cloud computing provides the illusion of infinite computing resources available on demand, offers highly customizable, on-demand services and enables access for IT services without significant investment (Sagawa et al., 2009; Sterling & Stark, 2009; Sosinsky, 2011). It also provides: (a) the user to get rid of operating and maintenance costs in relation to IT (b) flexible, dynamic and efficient use of IT resources (c) Instantly scalable infrastructure and load balancing (d) rapid access to new resource capabilities without incurring the delays implicit in upgrading and expanding local resources and personnel to manage them (e) responsive delivery of services and higher service quality (Vaquera et al., 2009; Sterling & Stark, 2009; IBM, 2008). Naturally, issues of privacy, confidentiality, security, reliability and vendor lock-in stand out as the major concerns regarding the technology (Buyya, Broberg, & Goscinski, 2011, Sterling & Stark, 2009; Gartner, 2008; Sosinsky, 2011; Shacklett, 2011).