I saw this article on Patterns and Strategies for Building Document-Based Web Services linked on ServerSide.com this morning.
I had a little thrill when I first saw the title: most of my recent work has been designing and writing a web based document repository (a 'Knowledge Management' application). I am extremely interested in managing different document types, searching, automatic categorization (not done in my current project), etc.
The linked article is on a different subject, but still very interesting: on document based interactions instead of RPC type interactions. In other words, using SOAP for RPC style communication is (in my opinion) an overkill. I think that SOAP is best used for requesting a complex structured document. Something like XML-RPC is much better for simply RPC-type communication. This point is discussed both in the linked article and Michael Daconta's (et. al.) useful book The Semantic Web.