In my previous two columns, I've explored some of the more common enterprise application integration (EAI) technologies (such as message- and database- oriented EAI engines) on the market. These technologies often offer adequate solutions to various types of integration problems. However, they are not viable in certain circumstances. Message-oriented EAI tools often don't provide intelligent routing capabilities by themselves, and sometimes there are serious scalability issues with database-oriented EAI toolsets. The solution to these problems is the middleware of middleware, the cream of the crop, the pinnacle of the EAI market: the solution is message broker technology.

Because of the way they handle integration tasks, message brokers are almost unlimited as to the types of applications they can integrate. Their use of "adapters" makes complex processing easier and, in some cases, transparent to users. They also provide a friendly graphical user interface (GUI) to facilitate easier use. Finally, they have intelligent routing capabilities that enable transmission accuracy and efficiency of the thousands of messages that flow through the EAI infrastructure.

One problem that traditional message-oriented and database-oriented EAI tools face is that, for various reasons, they are sometimes limited in the types and numbers of applications they can integrate. Message brokers solve this problem fairly handily. The best message brokers will offer any-to-many publish/subscription capability. This means that any application can receive any message from any other application (provided, of course, that the applications are part of the same EAI infrastructure). Multiple applications are also simultaneously able to receive a particular message from any connected application that is publishing that message. Any-to- many connectivity provides a sound, efficient infrastructure for EAI strategies and is a must-have for almost any EAI project.

This expansive connectivity capability is accomplished by the use of adapters. Adapters are nifty information-mapping layers between source and target applications. Adapters make the inner-workings and complexities of message transformation transparent to users. There are basically four types: thin, thick, static and dynamic. Adapters can come in multiple combinations of each type.

Thin adapters are usually simple application program interface (API) connectors. Thin adapters map source and target interfaces to a common interface. In essence, they connect multiple APIs to allow virtually unlimited application integration combinations. As a drawback, however, many thin adapters require a lot of complex programming. Thick adapters solve this problem by incorporating sophisticated software, with its concomitant functionality, directly within the adapter. Thick adapters make data mapping tasks more transparent to users and programmers than thin adapters. Thus, it's less painful to implement thick- adapter technology because it's easier for end users and programmers to use.

Static adapters are just that - static. They have to be encoded manually with information-mapping instructions. They are not really adaptable and must be updated by hand if database schemas change. Dynamic adapters have the adaptability that static adapters lack. They are intelligent and can read database schemas to learn about schema updates and adapt to them, so that the integration tasks are never interrupted by schema changes. For example, if the field Product_Code changes to Prod_Num, dynamic adapters can pick up on this change and adapt to it.

Message brokers also offer user-friendly GUI interfaces. Many older message- and database-oriented EAI tools required that trained programmers define connection logic, business rules and transformation schemas based on user input. Most message-broker GUIs allow ordinary users to perform these tasks. Some of the newer GUIs also offer wizards that walk users through these tasks and allow them to drill down to very fine levels of detail granularity within the various applications connected to the EAI infrastructure.

Finally, in addition to facilitating more diverse integration capabilities and simplifying the complexities of application integration to users, message brokers offer a really big advantage over traditional message-oriented EAI tools. Message brokers offer intelligent message routing capability. Intelligent routing means that the message broker can actually identify the type and target of a message from a particular source and route it to the appropriate target. They can also perform any transformations that may be necessary in order to make the message decipherable to the target application. Additionally, this routing and/or transformation is performed almost instantly, so the routing is performed efficiently as well as accurately.

I think that message broker technology is probably the most robust EAI technology on the market right now. Of course, vendors that use XML as an integration standard are making a serious run at gaining EAI market share. However, XML is still a burgeoning technology that doesn't have all the kinks worked out. It has tremendous potential, but probably for a few years down the road. Message brokers are here now, and they solve some very sticky integration problems. Remember, no one tool or technology is a silver bullet. The more you know, the more options you have open to solve your problems effectively.

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