In today’s world, it is essential for a business to provide a seamless and continuous service to its customers. Such an always-on service is required, not only for the strong competitive environment but also because of the fact that most the customers also have to offer seamless and continuous service to their own customers. In this chain, failure of one of the systems even for a short time can result in a disaster in the entire service chain. A wise approach to provide a continuous service should consider all possible failure areas in a computer-based information system. Since hardware and software are vulnerable to a myriad of problems that can halt the normal operation of a system, an ideal solution should not only consider both of these two components, but also should seek to find ways for them to work in support of each other against a malfunction. This chapter is an attempt to develop a model that provides this functionality. Service oriented architecture (SOA) is implemented in the model due to its tenets that are suitable for such functionality.
TopSoftware Component: Service Oriented Architecture
Although SOA can be defined in several ways, all definitions can be categorized in two main perspectives, namely business perspective and technical perspective. Business perspective can be analyzed in terms of business processes and business services, whereas technical perspective can be analyzed in terms of software components and operational resources. The two perspectives, their components, and their interrelationships are illustrated in the Figure 1.
Figure 1. SOA with Technical and Business Perspective (adapted from OMG)
From the business perspective, which is seen as top level in the figure, SOA is an architectural style that guides all aspects of creating and using business processes (Newcomer & Lomow, 2005). In this view, business processes and their management are highlighted and Business Process Management (BPM) concept arises. BPM can be defined as the method of efficiently aligning an organization with the wants and needs of clients. Business perspective contains the interaction between business services and business processes. A business process can contain one or more business services, and a business service can be used in one or more business processes.
The technical perspective is depicted in the lower half of the figure. According to this perspective, SOA can be defined as a kind of distributed computing that is designed to allow the communication of software components, namely services, across a network. In this view, services are performed by software components and SOA contains interactions of these software components in a distributing computing environment. Under services, there are some operational resources such as database servers or mainframes. At a higher level of abstraction, business processes and services are implemented through the technical level which contains software components and operational resources.
In this environment, SOA can be defined as follows:
“A service-Oriented Architecture (SOA) is a software architecture that is based on the key concepts of an application frontend, service, service repository, and service bus. A service consists of a contract, one or more interfaces, and an implementation” (Krafzig, Banke & Dirk, 2005, p.57).