Joe Gregorio at XML.com - XML.com: How to Create a REST Protocol:

"If you follow web services, then you may have heard of REST. REST is an architectural style that can be used to guide the construction of web services. Recently, there have been attempts to create such services that have met with mixed success. This article outlines a series of steps you can follow in creating your protocol--guidance that will help you get all the benefits that REST has to offer, while avoiding common pitfalls."