Self Service HRMS and AME

Objective:

In the previous article Request Response Patterns in SOA we have learned about the different types of Request Response Patterns in SOA. In this article we will learn about the Introduction to Service Oriented Architecture.

Introduction to Service Oriented Architecture(SOA):

SOA is is an IT strategy that organizes the discrete functions, contained in enterprise applications into interoperable, standards-based services to be combined and reused quickly to meet business requirements.

Service-oriented architecture attempts to overcome many of the shortcomings of earlier integration technologies by embracing the concept of a service. A service is a discrete, decoupled unit of business functionality that is exposed and available to (ideally) all applications in the enterprise.

Services are the building blocks for a SOA-enabled application. They have functionality-described standard interface and message structure definitions. Multiple services are assembled and reused to more quickly create applications that can better support changing business processes.

The SOA approach to software systems enables a consumer of a service to be decoupled from the service provider. With SOA, services are accessed by using standard protocols (the glue), which enable interoperability from decoupled functions.

When embarking on a SOA approach to systems integration, integrators begin by examining business process requirements to identify functionality to be used as a ―service‖ unit to help complete a business process. A service portfoliois identified from a set of services that are required for implementing one or more business processes within a business domain. A service portfolio can be realized by a combination of new and reused functionality. Existing functionality can be wrapped as services by using the adapter technology. New services can be created with SOA-enabled technologies, including web services, SCA composite applications, BPEL, and a service bus. When a collection of services has been identified to serve a business process, it is recommended to store information about these services, their interfaces, and their message structures in a common location such as an enterprise repository. This facilitates sharing and reusability from design through production. Coupled with a service registry, an enterprise repository can migrate runtime service information into the development, test, and production operational environments. Coupling an enterprise repository and a service registry enables an organization to implement strong SOA governance strategies for services throughout a service’s life cycle, from the design-time environment to the runtime environment.

When a satisfactory service portfolio is created, the necessary services are assembled to form a composite application to address a specific business requirement. Services are reused as appropriate in multiple composite applications. As a result, development time and redundant functionality are dramatically reduced.

Service Component Architecture:

Service component Architecture(SCA) is a set of specifications that describe a model for building applications by using a service oriented Architecture.

• Services are assembled to form a composite application that creates a solution that addresses a specific business requirements.

• Composite applications may contain new services and business functions from existing systems and applications.

• SCA provides a model for both the composition of services and the creation of service components, including reuse of existing application functions.

The Service Component Architecture (SCA) specification provides a programming model for building applications and systems based on a SOA approach. SCA is based on the concept that a business function is provided as a series of services. These composite applications may contain new services (specifically for the application) and business functions from existing systems and applications (reused in the composite application). SCA provides a model for both the composition of services and the creation of service components, including reuse of existing application functions.

When assembled together into a composite application, they are managed, maintained, and deployed together. This streamlines and simplifies management of cooperating service components compared to earlier technologies that managed SOA applications as a set of individual services. Because its functionality can be exposed as a service through service entry points, the SOA composite application is itself a coarse-grained service.

SCA is a collection of specifications.

Assembly model specifications define a standard set of XML elements that are used to define the structure and configuration of an SCA compositeapplication.

Client & implementation (C&I) specifications define an implementation language, such as:

• BPEL:The WS-BPEL Client and Implementation (BPEL C&I) model specifies how WS-BPEL processes can be used as SCA components.

• Java, C++, PHP:This specifies language-specific APIs and annotations, which enable the creation of service components and service clients that are built in these languages.

Services are business functions that form the foundation for using a SOA approach to building applications. SOA applications aggregate functionality of related services to automate a business process. In order to reuse services (a fundamental goal of SOA), service functionality must be described by using standard interface and message structures.

SOA-based approaches have, naturally, embraced many of the message standards illustrated in the graphic in the slide, including XML, XSD, and SOAP. These document structures are easily exchanged by using standard Internet protocols such as HTTP. This results in easier interoperability across intranet and Internet networks. Discovery and description standards such as WSDL and UDDI contribute to the reusability of services and help achieve independence of hardware, operating systems, and implementation languages.

As their names suggest, the WS-Security and WS-Reliable Messaging standards describe standards for secure and reliable message delivery among service-based applications.

BPEL provides XML grammar for describing a business process as a series of activities.

The Service Component Architecture (SCA) and Service Data Objects (SDO) specifications are works in progress, guided by the OASIS organization. This work may lead to a new collection of standards with a SOA-enabled approach in mind.

Benefits of SOA:

1. Reusability: Existing functionality within an application is reused across business organization and processes.

2. Interoperability: communication between services is not dependent on platform. Services are loosely coupled to application.

3. Scalability: Applications are flexible to changing business requirements.

4. Cost efficiency: cost are reduced and delivery of new functionality is accelerated because existing resources are reused and integration of business resources is standards based.

Varun Kapila

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