What's the difference between a "distributor" and a broker?

[David Hull <dmh@tibco.com>]

A distributor is just an object that encapsulates the delivery mechanics for some set of subscriptions.  The only message exchange it must implement is to receive raw messages from the NP (I originally had "NotificationConsumer, but that requires notify).  A Distributor doesn't implement NP or register publishers, so it's definitely not a broker.

A distributor might implement GetMessage (if it's a queue for pull-based notification), or {Add,Remove}Recipient or TweakLoadBalancing (if it's doing 1-of-N/Shared State), or Pause/Resume, or whatever.  Naturally, we have a stake in defining some of these additional interfaces.