T2: ackRequested attribute in Via element

Section 8.7 does not clearly indicate the 
circumstances under which the ackRequested attribute should be set (to Signed or 
Unsigned). Is this governed by the ReliableMessaging and NonRepudiation element 
for the DocExchange associated with the DeliveryChannel that is being 
used?

 

In particular, when an error is encountered in 
processing a message, what should be the strategy for setting the ackRequested 
attribute in the error message? In other words, under what circumstances, if 
any, are error messages to be sent reliably?

 

Thanks,

-Arvola