With this middleware approach, you wrap your business logic with interfaces that define the rules for interacting with that logic. Document-oriented middleware , such as message queuing systems, focuses on integration via document passing. With this middleware approach, you process business documents by posting them to message queues, where another processing entity can retrieve them and act on them. The message queues decouple applications from one another and allow overall processing to proceed asynchronously. While many words have been wasted arguing over which of these two middleware approaches is superior, the fact is that both approaches have merit under different circumstances.
Most enterprises use a mixture of the two approaches to satisfy their application integration needs.
Web services are evolving out of both of these middleware approaches. Not surprisingly, many of the same technical issues that we've been battling in the middleware space for years interface definition, transactions, message queue persistence, recovery, and security, to cite a few examples are still problematic, perhaps even more so, in the Web services space. Evolution from the EDI Perspective With all the hype currently surrounding e-business, you'd think it was brand new. It works, but it's fairly expensive to implement and deploy. The high costs of EDI are due primarily to the need to establish proprietary communication networks called value-added networks, or VANs, between EDI participants.