ietf-nntp Empty list on specific group / GROUP response

[Joao Prado Maia]

Hi everyone,

I have been following this mailing list by the web archive interface for a 
while, but I decided it is easier to read everything using pine ;)

I'm currently developing a Python based NNTP server to act as a gateway to 
web based message board software, but I'm confused about the corner case 
of when a group is empty and a client selects this group (i.e. GROUP 
group_name)

Quoting from the new NNTP draft:


             If the group is empty, one of the following three situations 
             will occur. Clients MUST accept all three cases; servers MUST 
             NOT represent an empty group in any other way. 
              
             The high water mark will be one less than the low water mark, 
             and the estimated article count will be zero. Servers SHOULD 
             use this method to show an empty group. This is the only time 
             that the high water mark can be less than the low water mark. 
             All three numbers will be zero.


Now what exactly does the last paragraph mean ? Maybe it is my english 
failing on me, but it first says that on the case that the group is empty, 
the response should be three zeros. However, it also says:


             This is the only time that the high water mark can be less 
             than the low water mark.


When would the high water mark be less than the low water mark ? On this 
case both would be zero, correct ? I would appreciate some more details 
about this.

Also, it would be very nice to have specific examples of the behavior of 
the NNTP server on these cases, as the wording is not the clearest one.

Regards,
Joao Prado Maia