What is Service Oriented Architecture?
SOA describes an information technology architecture that enables distributed computing environments with many different types of computing platforms and applications. In practical terms, this means companies can benefit from the unimpeded flow of information that is the hallmark of connected systems.
Web services are one of the technologies that help make SOAs possible. Microsoft.NET, Microsoft’s strategy for Web services, has provided the building blocks necessary for SOA to be achieved.
The Business Context of Service Orientation
Service orientation is a means for building distributed systems. At its most abstract, service orientation views everything – from the mainframe application to the printer to the legal secretary to the overnight delivery company – as a service provider.
Service providers expose capabilities through interfaces. Service-oriented architecture maps these capabilities and interfaces so they can be orchestrated into processes. The service model is "fractal": the newly formed process is a service itself, exposing a new, aggregated capability.
Fundamental to the service model is the separation between the interface and the implementation. The invoker of a service need only understand the interface; the implementation can evolve over time, without disturbing the clients of the service.
The same interface can be offered by many implementations; several key benefits of service orientation derive from this abstraction of the capability from how the capability is delivered.
Developers
To developers and solution architects, service orientation is a means for creating dynamic collaborative applications. By supporting run-time selection of capability providers, service orientation allows applications to be sensitive to the content and context of a specific business process, and to gracefully incorporate new capability providers over time.
IT Managers
To the IT manager, service orientation is a means for effectively integrating the diverse systems typical of modern enterprise data centres. By providing a model for aggregating the information and business logic of multiple systems into a single interface, service orientation allows diverse and redundant systems to be addressed through a common, coherent set of interfaces.
Chief Information Officer
To the chief information officer, service orientation is a means for protecting existing IT investments without inhibiting the deployment of new capabilities. By encapsulating a business application behind capability-based interfaces, the service model allows controlled access to mission-critical applications, and creates the opportunity for continuous improvement of the implementation behind that interface.
Business Analyst
To the business analyst, service orientation is a means of bringing information technology investments more in line with business strategy. By mapping employees, external capability providers, and automation systems into a single model, the analyst can better understand the cost trade-offs associated with investments in people, systems, and sourcing.
Organisation
To the Organisation as a whole, service orientation is a crucial prerequisite to creating connected systems. Connected systems are applications that leverage the network to link the actors and systems that drive business processes.
In other words, you build connected systems on an application model that transcends any one device, crosses boundaries respectfully, and rejects the restrictions of synchronicity. Connected systems pull together a constellation of services and devices, to more effectively meet your business challenges.
IT Strategy Focused on Connectivity
Driven by the need to achieve greater insight into business activities, enterprise IT departments are seeking effective and expedient means to integrate their application portfolios.
To achieve transparency and coherency, organisations must create these connections. They must connect systems to create consistent management of information. They must connect human and technical capabilities to create consistent business processes. They must connect workers to create collaborative teams. They must connect organisations to create effective value chains.
With its emphasis on a common model for invoking capabilities, service orientation is at the core of an effective connected-systems strategy.
Services and Connected Systems
In the context of computer component models, a service is a program that communicates by exchanging messages. Said another way, a service is a unit of application logic whose interface is defined purely by the messages it will accept and send.
With the development of messaging standards based on Extensible Mark-up Language (XML), service orientation is quickly becoming the mainstream approach for building connected systems.
The inherent challenge in connecting diverse systems is the translation of platform-specific information and procedural models through a common language. XML, XSD, WSDL, UDDI and WS- specifications, such as WS-Security and WS-Policy, are the first constructs of this growing common language.
Without the interoperability provided by a virtual platform based on broadly supported standards, service orientation requires significant expertise in protocol design, and questionable return on investment. Without Web services that connect your enterprise capabilities across heterogeneous platforms, service orientation is significantly less valuable to you and your organisation.