Semantics: full-duplex related semantics ...

[wenbozhu]

7.5 briefly touches this topic.

Responses (both final and interim) can be sent at any time after a request is received, even if it is not yet complete

More explicit descriptions are helpful, such as:

1. responses can be sent at any time, successful for failed ones
2. responses may be completed before requests are completed. This is described for 100-continue but should not be limited to 100-continue.
3. for 2), should a client that sees a failure response continues sending the remaining request content?

[wenbozhu]

3. is somewhat addressed in http/1.1 messaging when the server also closes the connection

[mnot]

For (1) and (2), we could adjust to say

All responses, regardless of status code (including non-final responses), can be sent (and complete) at any time...

(3) is situational. We could say something like 'A client that receives a response to its request while that request is still being sent SHOULD continue sending the request, unless some other signal indicates otherwise.' (with appropriate references, perhaps).