What is deferred parsing in the context of WESB?

Certain types of mediations have been optimized for WESB and deliver improved performance. This specialized optimization can be regarded as a kind of fast path through the code and is in addition to any general optimization of the WebSphere ESB mediation code. The optimization is known as deferred parsing. As the name implies, parsing the message can be deferred until absolutely required, and in several cases, parsing can be avoided altogether.