The Enterprise Application Integration (EAI) is defined as the process of integrating enterprise computer applications using computer software resources, mostly organizations have two type of applications front office and back office applications, to integrate them in such a way that they can communicate with each other when needed either by simple data passing or by collaborative approach of different applications. EAI is not just about sharing data between applications; it focuses on sharing both business data and business process. When we talk bout EAI it means system of systems which involves large scale inter dependency problems with multiple heterogeneous distributed systems across a network.

The back office applications are those related to the business processes or those applications that are transparent to customer and only the employees or managers have to deal with for example Decision Support System (DSS) or an Enterprise Resource Planning (ERP) and the front office applications are those which are visible to customer or which are for customer like Customer Relationship Management (CRM), before integrating these applications we have to know about the communication architectures available, it is thought that the best approach to EAI is to use an Enterprise service bus (ESB), which connects numerous, independent systems together. Although other approaches have been explored, including connecting database level, application layer or user interfaces. In ESB each independent application just need a connection to the bus so it can publish messages and subscribes to receive certain messages from the bus. This approach can be highly scalable.

"If you are involved with the operation or development of an enterprise application, there will doubtless come a time when you will need to integrate your application with another using the emerging preferred approach of messaging."

--Randy Stafford, Chief Architect, IQ Navigator

Enterprise Application Integration is related to middleware technologies such as message oriented architecture (MOA), data representation Tech. like XML to make the system highly transparent and scalable, when we talk about scalability web services is the only way because everything is coming to web now including web services like online shopping stores, online banking and even there are some virtual organizations, universities evolving which don’t have physical existence.

Web Services don’t just appeal to the technician, but directly address real business needs of today. The business should care about Web Services, particularly where they directly reflect some meaningful business concept, and especially where they are being exposed external – and hence are a reflection on the business.

“Web Services provide a simplified mechanism to connect applications regardless of the technology or devices they use, or their location. They are based on industry standard protocols with universal vendor support that can leverage the internet for low cost communications, as well as other transport mechanisms. The loosely coupled messaging approach supports multiple connectivity and information sharing scenarios via services that are self describing and can be automatically discovered."

Another approach for integration (of Web Services) is Service-Oriented Architecture (SOA) which is essentially a collection of services. These services communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity. SOA help businesses respond more quickly and cost-effectively to the changing market conditions they may face by promoting reuse and interconnection of existing IT assets rather than more time consuming and costly reinvention. In adoption of SOA you may face many challenges like SOA based environment include many services which exchange messages to perform different tasks so a single application can generate millions of messages to control and manage these messages and convert them to appropriate formats is quite a difficult task many vendors a working to address this particular challenge. Another issue regarding implementation of SOA is of security, applications which consume services, particularly those external to company firewalls, are more visible to other parties then traditional applications, to over come this security problem WS-Security suite of specifications is being developed to provide appropriate security.

"Software vendors have got into the habit of selling large proprietary stacks, but now there are too many out there which is a problem for integration,” “The key to integration is inter-operation…but [traditional methods] entailed people hand coding interfaces which increases time to market and reduces agility." iWay director Russell Scherwin.

Pattern of design, development, deployment, and management of applications and software infrastructure and frameworks in which: Applications are organized into business units of work (services) that are (typically) network accessible. Service interface definitions are first-class development artifacts. Quality of service (QoS) characteristics (security, transactions, performance, etc.) are explicitly identified at design time. Software infrastructure takes active responsibility for managing QoS and enforcing policy for service access and execution. Services and their metadata are cataloged in a repository. Protocols and structures within the architecture are, optionally, based on industry standards (e.g., the emerging SOAP stack of standards)

“Adopting SOA would also give the IT department the opportunity to raise its profile among senior managers, by positioning itself as a business enabler” Russell.

SOA should be thought of not just as a way of designing and documenting an "Architecture of Services", showing their relationships, dependencies, etc., but also a discipline by which we ensure that those Services are the right Services, delivered at appropriate levels of granularity, abstraction and generality that makes sense to both Service Provider and Service Consumer, reduces the effort (particularly on the consumer) to use a set of services to perform a particular objective, and truly minimizes the impact of change allowing Service consumers to switch providers and Service providers to switch implementations.

In today's highly dynamic marketplace, organizations are looking for a fast return on new and existing investments. Service-Oriented Architecture (SOA) is a framework that enables businesses to speed the delivery of IT projects cost-effectively and easily. SOA is an ideal framework to leverage functionality in old and new systems, allowing the organization to respond faster to new opportunities.

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