In Joe Gregorio's XML.com "The Restful Web" column - Constructing or Traversing URIs?:

"We have all these resources in our system, yet how do we enable the URIs of those resources to be discovered? Part of our specification, and of our running system, is being able to navigate around those resources. There are two types of solutions available to us; URI Construction and Hypertext Navigation. Let's look at both of them carefully to learn about their advantages and disadvantages."