• EAI (enterprise application integration) is a business computing term for the plans, methods, and tools
aimed at modernizing, consolidating, and coordinating the computer applications in an enterprise.
• Typically, an enterprise has existing legacy applications and databases and wants to continue to use them while adding or migrating to a new set of applications that
exploit the Internet, e-commerce, extranet, and other new technologies.
• the integration of various applications so that they may share information and processes freely.
• EAI is the unrestricted sharing of data and business
processes among any connected applications and data sources in the enterprise.
• 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 the Extensible Markup Language (XML).
• Middleware, message queueing, and other approaches.
• DataLevel EAI:
• is the process of moving data between data stores
• This can be described as extracting information from one database and updating it in another database.
• The advantage of data-level EAI is the cost of using this approach. Because we are largely leaving the
application alone, and not changing code, we don't need to incur the expense of changing, testing, and deploying the application.
• The technology that provides mechanisms to move data between databases, as well as reformats that information, is relatively inexpensive.
• Accessing data in the context of EAI requires an "end
run" around application logic and user interfaces in order to extract or load data directly into the database through an interface
• Coupling:
• coupling might be described as the act of bringing or coming together. Coupling refers to one components unnecessary dependence on another components implementation
• In terms of EAI, it's binding logic with data, logic with logic and/or data with data.
• it is really binding one application domain tightly to the next, and as such, it will require changing all coupled applications and databases in order to integrate them.
• a change to any source or target system means a change to the coupled systems as well. Coupling
creates one application and database out of many, with each very dependent on the other.
• Cohesion:
• is the "act or state of sticking together," or "the logical agreement.“
• The applications and databases are independent, and thus changes to any source or target system should not affect the others.
• The advantage of cohesion is the ability to share information between databases and applications, without regard for application and database changes.
• There are many technologies and techniques for moving the data from one database to the next, including database replication software, message brokers, and custom-built utilities.
• There are two basic approaches to data-level EAI and its accompanying enabling technology: database-to- database EAI and federated database EAI.
• Database-to-Database EAI
• Database-to-database EAI, like the point-to-point approach.
• Database-to-database EAI means sharing information at the database level and, by doing so, integrating
applications.
• Database-to-database EAI can exist in one-to-one, one- to-many, or many-to-many configurations
• We approach database-to-database EAI with traditional database middleware and database replication
software, such as replication features built into many databases or through database integration software.
• There are two types of solutions here.
• First, the basic replication solution moves information between databases that maintain the same basic
schema information on all source and target databases.
• The second solution is replication and transformation.
• The advantage of this EAI approach is the simplicity of it all. By dealing with application information at the data level, there is no need to change the source or target applications, generally speaking. This reduces the risk and cost of implementing EAI.
• Federated Database EAI
• federated database software is leveraged to allow developers to access any number of databases, using various brands, models, and schemas, through a single
"virtual” database model.
• This virtual database model exists only in software and is mapped to any number of connected physical
databases.
• The developers use this virtual database as a single point of application integration, accessing data from any number of systems through the same single
database interface.
• Application Level EAI:
• refers to the leveraging of interfaces exposed by custom or packaged applications.
• Developers leverage these interfaces to access both business processes and simple information.
• Using these interfaces, developers are able to bundle many applications together, allowing them to share business logic and information.
• The only limitations that developers face are the specific features and functions of the application interfaces.
• This type of EAI is most applicable to packaged
applications such as SAP, PeopleSoft, and Baan, which all expose interfaces into their processes and data, but do so in very different ways.
• In order to integrate those systems with others in the enterprise, we must use these interfaces to access both processes and data, extract the information, place it in a format understandable by the target application, and transmit the information.
• While many different types of technologies can do this, message brokers seem to be the preferred solution.
• Those concerned with the EAI problem and solution define EAI at either the data model level or the
business model level.
• They further break the business model level into three distinct types: the application interface level, the
method level, and the user interface level.
Application Interface-Level EAI
• Application Interfaces
• application interfaces are interfaces that developers expose from a packaged or custom application to gain access to various levels or services of the application.
• Sometimes these interfaces allow access to business processes; sometimes they allow access directly to the data. Sometimes they allow access to both.
• Developers expose these interfaces for two reasons.
The first is to provide access to business processes and data encapsulated within the applications they have created without forcing other developers to invoke the user interface or to go directly to the database.
• The second reason for exposing these types of interfaces is to provide a mechanism that allows encapsulated information to be shared.
• Interface by Example
• Let's say that a company maintains two systems: an ERP system that was just configured and installed and a
custom COBOL system that has been functioning for years. Each system exists on its own processor,
connected by the corporate network.
• Assume that the data-level EAI solution won't work due to the complexity of the databases and the binding of logic to the data. Thus, in order to integrate the old and new applications, the natural point of integration
should be application interfaces.
• Packaged Application Technology Architecture:
• Packaged applications found in enterprises today tend to use one of three distinct architectures: centralized, two-tier, and three-tier.
• Centralized architecture places both data application logic and user interfaces within the same machine, generally a mainframe or large minicomputer that houses a packaged application accessible by dumb terminals.
• There are a number of advantages to centralized architecture.
• First, because the data, process logic, and user interface all exist together on the same processor, maintenance is much easier than in traditional distributed environments.
• Second, integration is more easily accomplished within one machine than among several
• Two-tier architecture is physically and logically
separated onto just two layers (tiers), the client and the server. These two tiers are connected by a network
• The client always contains the user interface, but it may or may not also contain the business logic. Obversely, the database always contains the data, but it may or may not contain business logic.
• Placing the business logic on the client means having a
"fat" client. Placing the business logic on the database means having a "thin" client.
• The three-tier architecture is very similar to the two- tier architecture. The significant difference is the
placement of an application server between the client and the database to provide a location for the business logic
• The middle tier, or application server, provides almost all application logic-processing services.
• the client only deals with the interactions with the user, while the database only deals with the processing of
the data. The middle tier, or application server, provides almost all application logic-processing services.
• Types of Interfaces
» Full-service interfaces, provide access to the business services level, the data services level, and the object level
» Limited-service interfaces are the most common interfaces, typically allowing access to only one level
» Controlled interfaces provide only a bare minimum of features and functions
• Method-level EAI:
• is the sharing of the business logic that may exist within the enterprise.
• For example, the method for updating a customer record may be accessed from any number of
applications, and applications may access each other's methods without having to rewrite each method within the respective application.
• There are two basic approaches: You may create a
shared set of application servers that exist on a shared physical server, such as an application server, or you may share methods already existing inside of
applications using distributed method-sharing technology such as distributed objects.
