[Standards] Response Stream Namespace Qualification

[Mike Wacker]

I saw this excerpt in RFC 6120, 4.8.2: An entity MAY declare a "content 
namespace" as the default namespace for data sent over the stream (i.e., 
data other than elements qualified by the stream namespace). If so, (1) 
the content namespace MUST be other than the stream namespace, and (2) 
the content namespace MUST be the same for the initial stream and the 
response stream so that both streams are qualified consistently. The 
content namespace applies to all first-level child elements sent over 
the stream unless explicitly qualified by another namespace (i.e., the 
content namespace is the default namespace).

Reading that section, it suggests that the initial and response stream 
should always be qualified consistently, not just if the initiating 
entity declares a content namespace (e.g.: if the initial stream uses 
the stream namespace as the default namespace, then so should the 
response stream). However, this section on content namespaces is the 
only time the RFC mentions anything about qualifying the two streams 
consistently. If they are supposed to be qualified consistently, SHOULD 
or MUST they be qualified consistently?

More importantly, would it be reasonable to expect that some clients 
would assume the initial and response streams are qualified in the same 
way instead of checking the stream header of the response stream to see 
how the response stream is qualified (in case it's qualified differently 
than the initial stream)?