Re: [ws-rx] NEW ISSUE: correct form of SeqAck when RMD has receivedno messages

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

Seems like a good solution.

Another possible solution is for the receiver to send a NACK for message 
# 1 (since sending an ACK for a non-existent message seems a little 
weird). But this does not contain as much information as a AckRange with 
Upper="0" and Lower="0". The scenario outlined in the description of the 
issue can also occur when the sender has transmitted not just a single 
message but several messages, all of which have been lost. Sending a 
NACK for message # 1 says that the receiver has not receiver #1, but 
says nothing about the subsequent messages. Whereas sending an ACK for 
message # 0 (and only that) says that the receiver has received nothing .

OTOH, if the wsrm:MessageNumber optional element in wsrm:AckRequested is 
present, then the receiver will know exactly how many message have been 
sent but not received and then can indeed send a NACK for the 
appropriate messages.

I'm curious as to why wsrm:MessageNumber is optional. Wouldn't it make 
more sense to make it mandatory? This essentially lets the receiver know 
the last message number sent by the sender -- seems like the sender 
would always want to send that info in an wsrm:AckRequested message.

-Anish
--

Christopher B Ferris wrote:
> Title: What is the correct form of SeqAck when RMD has received no 
> messages
> 
> Description: Consider the following scenario: an RMS establishes a 
> Sequence with 
> CreateSequence and transmits a single message that is NOT received by the 
> RMD. It then follows
> that with an AckRequested message. What is the correct form of the 
> SequenceAcknowledgement
> expected? Should one be sent?
> 
> Justification: The specification and schema require that a 
> SequenceAcknowledgement element
> have at least one AcknowledgementRange child element (or a Nack) Yet, 
> MessageNumber values
> start at 1 and increment monotonically by 1 for each successive message in 
> a Sequence. Zero (0)
> is not a valid MessageNumber. 
> 
> Target: core
> 
> Type: design
> 
> Proposal: Recommend that an RMD be required to respond with a 
> SequenceAcknowledgement
> element containing exactly one AcknowledgementRange child element that has 
> both the
> @Upper and @Lower attributes each carry a value of "0" to signify that no 
> messages have been
> received for a given Sequence. e.g.
> 
> <wsrm:SequenceAcknowledgement 
> xmlns:wsrm="http://docs.oasis-open.org/whatever";>
>   <wsrm:Identifier>http://example.org/mysequence/1234</wsrm:Identifier>
>   <wsrm:AcknowledgementRange Upper="0" Lower="0">
> </wsrm:SequenceAcknowledgement>
> 
> Related issues: none
> Cheers,
> Christopher Ferris
> STSM, Emerging e-business Industry Architecture
> email: chrisfer@us.ibm.com
> blog: http://webpages.charter.net/chrisfer/blog.html
> phone: +1 508 377 9295
>