In the software industry today as we address the interenterprise and its business problems, the solutions to these problems are becoming increasingly complex. They span several tiers of distributed systems and involve several disjointed applications that must somehow talk to each other - efficiently, repeatedly, and securely. Enterprise applications must meet the stringent requirements placed on performance, reliability, flexibility, and ease of use. One of the biggest challenges is that information must be integrated from disparate, loosely coupled systems both within and between businesses (B2B) to support electronic business. Doing business over the Internet demands high performance, low latency, and reliable data exchange across large networked systems.

Ultimately there's a need to bind disparate applications into a single, unified enterprise application. The development of Enterprise Application Integration (EAI) components allows applications to share processes and data in a distributed environment. EAI tries to address this problem in a generic fashion by leveraging standard technologies to provide solutions that can be applied across a variety of industry verticals.

The emergence of XML as a standard technology enabler in the last few years has particular significance for EAI. Since XML enables the expression of data in a ubiquitous format, it offers a mechanism for externalizing data. Thus it acts as an enabler that facilitates the sharing of data across different applications. It complements and supplements EAI message/integration brokers for integrating applications. When using the point-to-point approach, integrating applications become messaging infrastructures that can span multiple applications. This can be accomplished with any number of message-oriented middleware (MOM) products. However, wrapping the messages in message envelopes still leaves open the issue of defining the standard data formats and processing. MOMs can help transport messages between two applications that agree on a message format. However, when data has to be shared by multiple applications, a more generic mechanism for defining and processing application specific data is still needed. XML tries to address this need.

Organizations must understand both business processes and data, and select which processes and data elements require integration. This involves integration at several levels, including data, application interface, method, and UI. XML and DOM enable EAI by simplifying data transformation and portability. Web-tier integration servers support EAI by extracting business data from systems and translating it into XML. Normalized data in the form of XML can be more easily interpreted and used to interface with back-end systems.

Data transformation is a critical component of EAI as it allows data from one application to be transformed for use in another. XML addresses this need through its XSLT specification. XSLT provides a clear separation of the transformation rules from the application programming effort and its seamless integration with XML. XML also eliminates the need for custom adapters when integrating packaged applications. When coupled with HTTP, XML becomes a ubiquitous middleware for B2B. Major application vendors are adding XML-based application program interfaces to their application suites. Thus the market for XML-based adapters for popular applications is growing rapidly.

As mentioned earlier, XML facilitates document flow, but EAI solutions need to address event-based, process-flow paradigms as well. XML also fits in well with workflow engines that support both mechanisms. Integrating different applications involves defining business flows and consequently managing transactions that span distributed applications that may reside in different enterprises. This type of business transaction management is achieved through the use of Transaction Processing (TP) monitors.

In short, XML offers a compelling technology that facilitates EAI by playing a crucial role wherever data expression and transportation are involved. As we see the emergence of more comprehensive enterprise-level applications, we should also see a greater variety of offerings from XML vendors that support interapplication data flow and processing.