ietf-nntp New wording on article numbers
Clive D.W. Feather
clive at demon.net
Fri Dec 27 12:32:43 PST 1996
As promised. Comments welcome.
Proposed wording for RFC 977bis concerning article numbering.
=============================================================
New section:
News is divided into named groups. Within each group exist articles.
Each article has three relevant properties:
- A Message-ID, which is unique over all articles in all groups; if
an article occurs in more than one group, it has the same Message-ID
in all groups.
- An arrival timestamp, giving the time it arrived at the server.
- An article number, which is unique only within the group; different
articles in different groups may have the same number, and an
article that occurs in more than one group may have different
numbers in each group.
The server MUST ensure that article numbers are issued in order of
arrival timestamp; that is, later arriving articles MUST have higher
numbers than earlier arriving ones. The server SHOULD allocate the first
unused number to each new article.
Article numbers MUST lie between 1 and 999999999 inclusive [this allows
one article per second for 31 years]. The client and server SHOULD NOT
use leading zeroes in specifying article numbers. If the server loses
record of the most recent article number in a group, it MUST reset to a
higher article number.
3.2. The GROUP command
3.2.1. GROUP
Replace the paragraph:
The successful selection response will return the article numbers of
the first and last articles in the group, and an estimate of the
number of articles on file in the group. It is not necessary that
the estimate be correct, although that is helpful; it must only be
equal to or larger than the actual number of articles on file. (Some
implementations will actually count the number of articles on file.
Others will just subtract first article number from last to get an
estimate.)
by the following paragraphs:
The successful selection response will return the article numbers of the
first and last articles in the group at the moment of selection, and an
estimate of the number of articles on file in the group. The estimate
MUST be at least the actual number of articles available. (Some
implementations will actually count the number of articles on file.
Others will just subtract first article number from last to get an
estimate.)
The last article number MIGHT be less than the first article number. In
this case, there are no articles in the group and the estimated count
MUST be zero.
The set of articles in a group may change after the GROUP command is
carried out. That is:
* articles may be removed from the group;
* articles may be reinstated in the group with the same article number,
but those articles MUST have numbers no less than the first article
number in the response;
* new articles may be added with article numbers greater than the last
article number returned in the response.
When a subsequent GROUP command for the same newsgroup is issued, either
by the same client or a different client, the first and last article
numbers MUST be no less than those in the previous response for that
newsgroup.
3.1.2. ARTICLE (selection by number)
Add the paragraph:
A previously valid article number might not remain valid if the article
has been removed. A previously invalid article number might become valid
if the article has been reinstated, but such an article number MUST be
no less than the "first" article number specified in the most recent
response to a GROUP command for that group.
3.5. The LAST command
3.5.1. LAST
Add the paragraphs:
There might be no previous article in the group, even though the current
article number is not the first one according to the last GROUP command.
Because articles can be removed and added, the results of multiple LAST
and NEXT commands might not be consistent over time.
3.9. The NEXT command
3.9.1. NEXT
Add the paragraphs:
There might be no subsequent article in the group, even though the
current article number is not the last one according to the last GROUP
command. Similarly (and unlike the LAST command) there might be a
subsequent article in the group even though the article number *is* the
last one; in this case, another GROUP command will return a higher
"last" value.
Because articles can be removed and added, the results of multiple LAST
and NEXT commands might not be consistent over time.
--
Clive D.W. Feather | Associate Director | Director
Tel: +44 181 371 1138 | Demon Internet Ltd. | CityScape Internet Services Ltd.
Fax: +44 181 371 1150 | <clive at demon.net | <cdwf at cityscape.co.uk>
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