DO NOT EDIT DO NOT EDIT Different set of concerns Client cares about processing or rendering Server cares about storing and making information available efficiently Keeping concerns separate allow client and server to evolve independently Messages always contain all data needed to process the request Including authentication information if required That doesn't mean you can't use cookies! That means you must use them responsibly The server keeps no session state around The client may Resources may be cached by any component, including the client, the server and any intermediary All resources are explicitly or implicitly marked as (not) cacheable All components use the same rules to speak to each other Makes it easy to understand the interactions A number of constraints are required to achieve this We will see them in a few minutes...