title: Should a given URI in a RESTful architecture always return the same response?
body: <p><em>This is kind of a follow-up question to <a href="https://stackoverflow.com/questions/2671582/rest-caching-and-authorizing-with-multiple-user-roles">this one</a>.</em></p>
  
  <p>So is having a unique response for any given URI a core tenant of RESTful architecture?  A lot of discussion here tends that direction, but I haven't seen it anywhere as a "hard and fast" rule.</p>
  
  <p>I understand the value of it (for caching, crawling, passing links, etc), but I also see things like the twitter API violate it (A request to <code>http://api.twitter.com/1/statuses/friends_timeline.xml</code> will vary based on the username given), and I understand there are times when it may be necessary--not to mention that a chronologically paged resource will also change as new elements are added.</p>
  
  <p>Should I strive for varied responses from the same URI to be eliminated altogether, or do I just accept that sometimes it isn't practical, and as long as I minimize its occurrence, I'll be in decent shape.</p>