BizTalk 2004 allows simple access to data inside an Orchestration by using Xpath. This can be used to read and write data as well as total message assignment. This sample shows different ways to access data using Xpath inside the Orchestration.
This sample will work for both BizTalk 2004 and BizTalk 2006.
Get more information from the original blog post on this topic: http://www.biztalkgurus.com/blogs/biztalk/archive/2004/10/25/Using-XPath-Inside-BizTalk-Orchestrations.aspx