[SAGA-RG] SAGA Message API Extension

[John Shalf]

Hi Andre,
In Chapter 2, the paragraphs explaining the message transfer  
requirements are a bit confusing.
	1) it says it supports multicast (which is inherently unreliable).   
I'm sure you mean to say a "message bus" (sort of like the Linux DBus  
concept), which would not specifically call out a particular network  
standard (multicast is more specific than a "message bus").
	2) It says the message must be received completely and correctly, or  
not at all.  This leaves some aspects of the reliability uncertain.   
For instance
		a) does this mean it must guarantee delivery of a message?  Or only  
that a delivered message does not contain errors?
		b) what about if the message arrives more than once? (eg. redundant  
copies of messages can occur in practice for a number of unreliable  
or semi-reliable messaging protocols).
		c) It says this document will not address things at a protocol  
level, but I think these issues are semantic and therefore must be  
addressed by the API.
		d) I think there are a number of attributes that users should be  
able to supply or query when opening a message service connnection.   
Like the JMS (Java Message Service), we should be able to specify  
whether this is a point-to-point (message queue) or a publish- 
subscribe (message bus) like interface.  The API should not require  
any work to support both since point-to-point is a sub-category of  
the message-bus, but it should be an attribute of the message  
interface that a user can force/specify in the opening of the  
connection.  Another thing to support is specification or query of  
the message service reliability (something that deserves at least a  
subsection to define.  That is, the document should define classes of  
reliability (just as done with other XML-based messaging APIs that  
even define intermediate cases for unreliable messaging that  
guarantee message arrival, but do not ensure that duplicate messages  
will not arrive).  The API should allow a user to specify these  
semantic attributes and will not allow a connection to be built if  
the underlying protocol for the message connection cannot meet those  
attributes.

-john

On Jan 16, 2007, at 11:17 AM, Andre Merzky wrote:
> Hi Folx ,
>
> here is the updated draft of the SAGA Message API, in
> preparation for OGF-19.  It is also available in CVS, as
> usual.
>
> We would be happy to get feedback on the list of course, so
> don't feel oblidged to hold back your comments for OGF-19
> :-)
>
> Cheers, Andre.
>
>
> -- 
> "So much time, so little to do..."  -- Garfield
> <saga_messages.pdf>