RE: Action Item

I'd think that almost any async pattern would allow messages to be
returned out-of-order, with the only exception being one where there
cannot be more than one outstanding request (and I'd consider that
"pseudo-synchronous").
 
Tony Rogers
tony.rogers@ca.com <blocked::mailto:tony.rogers@ca.com> 
 

  _____  

From: public-ws-addressing-request@w3.org
[mailto:public-ws-addressing-request@w3.org] On Behalf Of David Hull
Sent: Wednesday, 7 December 2005 7:22
To: Cahill, Conor P
Cc: John Kemp; ext Yalcinalp, Umit; public-ws-addressing@w3.org
Subject: Re: Action Item


Cahill, Conor P wrote: 

	 
	
	  

		When submitting a message for potentially asynchronous 
		processing, it would seem that the response message must
come 
		back on a different channel than that used to submit the
request.
		    

	
	I'm not sure this is the case.  There are many situations where
	the client and server can maintain a permanent connection
pipeline
	to asynchronously send messages back and forth where the server 
	is not able to separately connect to the client (most instant
	messaging services work this way).
	
	Conor
	
	
	  

A polling protocol should probably provide for 0 .. * messages coming
back on each poll (e.g., send request one, poll, no response, send
request two, poll again, get both responses).  Given this, one might
consider the combination of request messages flowing one way and poll
responses flowing the other as a sort of virtual channel, split across
multiple connections.

It occurs to me that I'm bringing in yet another notion of
asynchronicity here, namely that response messages may not arrive in the
same order as their corresponding requests.  This is a more general
definition, in that it can be realized by the "non-anonymous callback
EPR" pattern, by the polling pattern and by something
connection-oriented but duplex like an IM protocol.