Enterprise Application Integration

Middleware and enterprise application integration (EAI) are not completely orthogonal concepts. They are, however, distinct enough to warrant separate treatment. As we saw in Chapter 2, middleware constitutes the basic infrastructure behind any distributed information system. Initially, middleware was used to construct new systems and to link to mainframe-based systems (2-tier architectures). Later, it was used to distribute the application logic and to integrate the many servers created by 3-tier architectures.