Part 1 why services oriented architecture

Thus the need for services as much larger units of functionality than traditional functions or classes, lest the sheer complexity of thousands of such granular objects overwhelm the application designer. Services may also be wrappers for existing Legacy systems , allowing re-facing of old systems. SOA services are more loosely coupled than functions linked from libraries to form an executable. SOA services also run in "safe" wrappers such as Java or.

NET and in other programming languages that manage memory allocation and reclamation, allow ad hoc and late binding, and provide some degree of indeterminate data typing. As of [update] , increasing numbers of third-party software companies offer software services for a fee. In the future, SOA systems may [ original research? This has the potential to spread costs over many customers and customer uses, and promotes standardization both in and across industries.

In particular, the travel industry now has a well-defined and documented set of both services and data, sufficient to allow any reasonably competent software engineer to create travel-agency software using entirely off-the-shelf software services.

SOA as an architecture relies on service-orientation as its fundamental design principle. If a service presents a simple interface that abstracts away its underlying complexity, users can access independent services without knowledge of the service's platform implementation.

The following principles were proposed by Yvonne Balzer to guide development, maintenance, and usage of the SOA: [ 8 ]. The Microsoft Windows Communication Foundation team proposed the following principles for service-oriented design: [ 9 ]. In addition, one might take the following factors into account when defining a SOA implementation: [ original research?

Four common SOA types have emerged in order to improve physical design. This also assists in understanding interdependencies among services. This is the physical design of an individual service that encompasses all the resources used by a service. This would normally include databases, software components, legacy systems, identity stores, [ 13 ] XML schemas and any backing stores, e. It is also beneficial to include any service agents [ 14 ] employed by the service, as any change in these service agents would affect the message processing capabilities of the service.

The standardized service contract design principle, keeps service contracts independent from their implementation. The service contract needs to be documented to formalize the required processing resources by the individual service capabilities. Although it is beneficial to document details about the service architecture, the service abstraction design principle dictates that any internal details about the service are invisible to its consumers so that they do not develop any unstated couplings.

The service architecture serves as a point of reference for evolving the service or gauging the impact of any change in the service. One of the core characteristics of services developed using service-orientation design paradigm is that they are composition-centric. Services with this characteristic can potentially address novel requirements by recomposing the same services in different configurations.

Service composition architecture is itself a composition of the individual architectures of the participating services. In the light of the Service Abstraction principle, this type of architecture only documents the service contract and any published service-level agreement SLA ; internal details of each service are not included.

If a service composition is a part of another parent composition, the parent composition can also be referenced in the child service composition. The design of service composition also includes any alternate paths, such as error conditions, which may introduce new services into the current service composition. A service inventory is composed of services that automate business processes. It is important to account for the combined processing requirements of all services within the service inventory.

Documenting the requirements of services, independently from the business processes that they automate, helps identify processing bottlenecks. The service inventory architecture is documented from the service inventory blueprint, so that service candidates [ 15 ] can be redesigned before their implementation.

This umbrella architecture incorporates service, composition, and inventory architectures, plus any enterprise-wide technological resources accessed by these architectures e. This can be further supplemented by including enterprise-wide standards that apply to the aforementioned architecture types. Any segments of the enterprise that are not service-oriented can also be documented in order to consider transformation requirements if a service needs to communicate with the business processes automated by such segments.

Web services can implement a service-oriented architecture. Web services make functional building-blocks accessible over standard Internet protocols independent of platforms and programming languages.

These services can represent either new applications or just wrappers around existing legacy systems to make them network-enabled. Implementers commonly build SOAs using web services standards for example, SOAP that have gained broad industry acceptance after recommendation of Version 1.

These standards also referred to as web service specifications also provide greater interoperability and some protection from lock-in to proprietary vendor software.

Architectures can operate independently of specific technologies. Implementations can use one or more of these protocols and, for example, might use a file-system mechanism to communicate data conforming to a defined interface specification between processes conforming to the SOA concept. The key is independent services with defined interfaces that can be called to perform their tasks in a standard way, without a service having foreknowledge of the calling application, and without the application having or needing knowledge of how the service actually performs its tasks.

Many implementers of SOA have begun [ when? SOA enables the development of applications that are built by combining loosely coupled and interoperable services. These services inter-operate based on a formal definition or contract, e. The interface definition hides the implementation of the language-specific service. SOA-based systems can therefore function independently of development technologies and platforms such as Java,.

NET, etc. Services written in C running on. NET platforms and services written in Java running on Java EE platforms, for example, can both be consumed by a common composite application or client. Applications running on either platform can also consume services running on the other as web services that facilitate reuse.

This has extended the useful life of many core legacy systems indefinitely [ citation needed ] , no matter what language they originally used. SOA can support integration and consolidation activities within complex enterprise systems, but SOA does not specify or provide a methodology or framework for documenting capabilities or services. High-level languages such as BPEL and specifications such as WS-CDL and WS-Coordination extend the service concept by providing a method of defining and supporting orchestration of fine-grained services into more coarse-grained business services, which architects can in turn incorporate into workflows and business processes implemented in composite applications or portals [ citation needed ].

As of [update] researchers have started investigating the use of service component architecture SCA to implement SOA. Service-oriented modeling [ 2 ] is a SOA framework that identifies the various disciplines that guide SOA practitioners to conceptualize, analyze, design, and architect their service-oriented assets. The Service-oriented modeling framework SOMF offers a modeling language and a work structure or "map" depicting the various components that contribute to a successful service-oriented modeling approach.

The model enables practitioners to craft a project plan and to identify the milestones of a service-oriented initiative. SOMF also provides a common modeling notation to address alignment between business and IT organizations. A paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains. It provides a uniform means to offer, discover, interact with and use capabilities to produce desired effects consistent with measurable preconditions and expectations.

SOA represents an open, agile, extensible, federated, composable architecture comprised of autonomous, QoS-capable, vendor diverse, interoperable, discoverable, and potentially reusable services, implemented as Web services.

SOA can establish an abstraction of business logic and technology, resulting in a loose coupling between these domains. SOA is an evolution of past platforms, preserving successful characteristics of traditional architectures, and bringing with it distinct principles that foster service-orientation in support of a service-oriented enterprise.

SOA is ideally standardized throughout an enterprise, but achieving this state requires a planned transition and the support of a still evolving technology set. A service contract may have the following components: [ 21 ]. As of [update] the principles of SOA are being applied by network managers in their field. Some enterprise architects believe that SOA can help businesses respond more quickly and more cost-effectively to changing market conditions.

With SOA, the idea is that an organization can look at a problem holistically. A business has more overall control. Theoretically there would not be a mass of developers using whatever tool sets might please them. But rather there would be a coding to a standard that is set within the business. They can also develop enterprise-wide SOA that encapsulates a business-oriented infrastructure.

The objective of this tutorial is to provide guidance on the architecture and design of service-oriented systems. Part I covers basic concepts and impact.

SOA is not an architecture. SOA is not a system. SOA is a way of designing systems, an approach to system development, an architectural style, a design paradigm.

As an architectural style, SOA can be described in terms of components and connectors. The main components are the services, service consumers, and SOA infrastructure. For further information, see Guiding Principles on Independence and Objectivity.

Gartner Research. Roy Schulte , Yefim Natis Summary A service-oriented architecture is a style of multitier computing that helps organizations share logic and data among multiple applications and usage modes.

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