Δευτέρα, 13 Δεκεμβρίου 2010

SOA system on cloud environment


In the last years, the service-oriented architecture (SOA) has emerged as an architectural style allowing to build applications out of reusable components (services). The technology to realize SOA is web services and Business Process Execution Language (BPEL). SOA provides a programming model where new functionality is encapsulated on web services or web services are used as interfaces to existing heterogeneous applications and data sources. BPEL provides a model and a grammar for specifying web services compositions in the form of business processes and for externalizing the functionality of business processes as web services. The call of web services from process “invoke” activities enable to easily change the implementation of a service or replace a service without affecting the business process.

Cloud computing has been referred to as an architecture, a platform, an operating system, and a service, and in some senses, it is all of these. A basic definition of cloud computing is using the Internet to perform tasks on computers. It is an approach to computing in which resources and information are provided through services over the Internet, in which the network of services is collectively known as “the cloud.” The taxonomy of clouds is private, public and hybrid. Private clouds are on-demand infrastructures owned by a single customer, public clouds are run by third parties and hybrid clouds are a combination of public and private clouds. In cloud, there are three delivery models, namely infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS), but there are also other classifications available such as business process as a service (BPaaS).

BPaaS can be realized by composing SOA programming model with cloud computing. SOA enables to overcome technical interoperability and data exchange incompatibility issues and cloud enables to provide essential ubiquitous access to powerful and seamlessly integrated computer based capabilities as services. A BPaaS can be realized by the installation and configuration of a SOA platform on virtual images created by a IaaS (Amazon Elastic Compute Cloud - EC2) and the provision of this platform as a service. BPaaS usually enables business processes execution and monitoring, web services invocation, web services security support etc. With the use of a BPaaS, more machines can be added on demand as the processes gain more transactions. In addition, as cloud services are actually web services can be called from BPEL “invoke” activities as third party partners. Thus, it is possible for example in a BPEL process running on a public or private cloud to call a cloud service from a public cloud like Amazon’s Simple DB or Amazon’s Simple Storage Service (S3) in order to store/retrieve data to/from cloud virtualized servers.

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