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>