Service-orientation is a design paradigm for computer software in the form of services. The principles of service-oriented design stress the separation of concerns in the software. Applying service-orientation results in units of software partitioned into discrete, autonomous, and network-accessible units, each designed to solve an individual concern. These units qualify as services.
History of service-orientation principles and tenets
Service-orientation has received a lot of attention since 2003 due to the benefits it promises. These include increased return on investment, organisational agility and interoperability as well as a better alignment between business and IT. It builds heavily on earlier design paradigms and enhances them with standardisation, loose coupling and business involvement. The paradigm lost momentum in 2009; since 2014, renewed interest can be observed under the Microservices moniker. In technology, different vendor SOA platforms have used different definitions of service-orientation. Some vendors promote different principles and tenets over others, but a fair amount of commonality exists. Service-orientation inherits a small number of principles from earlier paradigms including object-oriented programming, component-based software engineering and open distributed processing. It is commonly acknowledged that several service-orientation principles have their roots in the object-oriented design paradigm. The two are complementary paradigms and that there will always be a need for both. Services also inherit a number of features of software components, including
Multiple-use
Non-context-specific
Composable
Encapsulated i.e., non-investigable through its interfaces
Open Distributed Processing combines the concepts of open systems and distributed computing, which are essential characteristics of service-orientation. The key features of ODP are all inherited by service-orientation, including federation, interoperability, heterogeneity, transparency and trading/broking.
Essential characteristics
was one of the first to provide a set of design guidelines referred to as his "four tenets of service-orientation", which he described primarily in relation to the Microsoft Indigo platform that was emerging at the time:
Boundaries are explicit
Services are autonomous
Services share schema and contract, not class
Service compatibility is based on policy
Other vendors and independent consultants have published their definitions of service-orientation and SOA, for instance, N. Josuttis in "SOA in Practice" and D: Krafzig et al. in "Enterprise SOA". An article in the December 2005 edition of the IBM System Journal entitled "Impact of service orientation at the business level" provided a study of how the service-orientation paradigm relates to fundamental componentization and the IBM Component Business Model. Paul Allen defines service orientation as a paradigm, with three main components: business architecture, Service-oriented architecture and software oriented management. Allen's book defines seven Service-Oriented Viewpoints :
Transparence
*Smoothness of customer’s experience in using the service.
Customer fit
*Ability to tailor offerings to variations in customer needs.
Partner connectivity
*Ability to use 3rd parties for performing commodity services
*Ability to offer a service to different partners
Adaptation
*Adapting to the changes in the marketplace.
Multi-channel capability
*Support the customer end-to-end through process, using different channels to achieve continuity.
*Offering same service through different channels.
Optimization
*Offering services in real time at high performance levels.
One-stop experience
*Catering to different needs of the customers through one set of services.
Allen uses the viewpoints as starting point for stating questions during the design process. Service-orientation has continued to receive increased recognition as an important part of the service-oriented computing landscape and a valid design approach to achieving service-oriented architecture.
