Enterprise Application Integration (EAI)

Enterprise Application Integration is an integration framework composed of a collection of technologies and services which form a middleware to enable integration of systems and applications across the enterprise. Fundamentally, it is all about sharing and distributing data and processes among different applications and data sources of that enterprise.

EAI could be divided into 4 integration levels:

1. Data Level
2. Application Interface Level
3. Method Level
4. User Interface Level

Data Level: It is actually a database-centric approach that involves the extracting of data from one database and updating it in other. At times the extracted data can be changed before entering it into that target database, for example, to apply specific business rules. It’s commonly done through ETL (Extract, Transform, and Load). 

The main benefits of this approach are its low cost and low risk profile. Because in this, we don’t have to make any modifications to the existing code of the application. So, we don’t need to undergo any expenses related to the developing, testing, or deploying any new sorts of these applications.

Application Interface Level: It consists of leveraging the interfaces distributed by custom or packaged applications to access business processes and easy information. Usually, this kind of integration is done in a three-step process:

1. Extract the information from one application through a provided application interface.
2. Convert the data in a format understandable by the target application.
3. Transmit the information to the target application.

The main benefits of this approach are the point that the interfacing between the different applications is easy due to the fact that the application interfaces are provided by application. A negative aspect of this approach is the cost of the message broker technology.

Method level: It is actually similar to application interface level but have a lower level of granularity. Here, idea here is not to share any business functions (as in application interface level), but to share directly the different methods used to compose a given business function. In this, methods can be reuse for business logic

User Interface Level: It’s commonly known as "Refacing" and consists of substituting existing text-based user interfaces of the legacy systems and graphical interfaces of PCs by a standardized interface, typically known as browser-based. This kind of integration is less expensive than any other approaches, as the code of the existing applications is not revised. However, this approach is then less flexible too.

Middleware is a mechanism that allows one entity (application or database) to communicate with another entity, or entities. It is the only solution that allows applications to communicate with one another. Middleware technologies are able to hide the complexities of the source and target systems, freeing developers from focusing on low-level APIs and network protocols, allowing them to concentrate on sharing information.

Advantage of EAI:

• Real-time
• Integrate and Connect between systems
• Secure and Scalable
• Lower Total Cost of Ownership
• Lesser development and support cost
• Faster Build

EAI encompasses methodologies such as:

• Object-oriented programming.
• Distributed, cross-platform program communication using message brokers with Common Object Request Broker Architecture and COM+. 
• Modification of enterprise resource planning (ERP) to fit new objectives. 
• Enterprise-wide content and data distribution using common databases and data standards implemented with XML.
• Middleware, message queueing, and other approaches.