In this article and the previous one, we have seen that Web Services can be classified into two broad categories: synchronous (RPC) and asynchronous (document-centric). While simpler, the RPC model tends to lead to tight coupling and is therefore less resilient to change. The asynchronous model provides many benefits, including loose coupling, asynchrony, and a business level interface.
One of the key technologies for an asynchronous architecture is a messaging infrastructure. Messaging systems and integration brokers provide many features currently not addressed by Web Services including transformation, content-based routing, workflow modeling, adapters, message warehousing, and management. A key decision that needs to be addressed when performing integration is whether to use a point-to-point or publish-subscribe topology. The former is often used with synchronous integration, whereas the latter is more often used with asynchronous integration.