Son-of-RFC1036:[Previous][Up to Table of Contents] [Next]
The Newsgroups header's content specifies which newsgroup(s)
the article is posted to:
Newsgroups-content = newsgroup-name *( ng-delim newsgroup-name )
newsgroup-name = plain-component *( "." component )
component = plain-component / encoded-word
plain-component = component-start *13component-rest
component-start = lowercase / digit
lowercase = <letter a-z>
component-rest = component-start / "+" / "-" / "_"
ng-delim = ","
Encoded words used in newsgroup names MUST not contain char-
acters other than letters, digits, "+", "-", "/", "_", "=",
and "?" (although they may encode them).
A newsgroup name consists of one or more components, which
may be plain components or (except for the first) encoded
words. A plain component MUST contain at least one letter,
MUST begin with a letter or digit, and MUST not be longer
than 14 characters. The first component MUST begin with a
letter; subsequent components SHOULD begin with a letter.
Newsgroup names MUST not contain uppercase letters, except
where required by encodings in encoded words. The sequences
"all" and "ctl" MUST not be used as components.
NOTE: The alphabet and syntax specified encom-
passes all existing names of widespread news-
groups, while avoiding various forms that are
known to cause problems. Important existing soft-
ware uses various non-alphanumeric characters as
punctuation adjacent to newsgroup names. (It
would, in fact, be preferable to ban "+" from
newsgroup names, were it not that several
widespread newsgroups related to the C++ program-
ming language already use it.)
NOTE: Much existing software converts the news-
group name into a directory path and stores the
articles themselves using numeric filenames, so
all-digit name components can be troublesome; the
"Great Renaming" early in the history of Usenet
included revisions of several newsgroup names to
eliminate such components.
NOTE: The same storage technique is the reason for
the 14-character limit. The limit is now largely
historical, since most modern systems have much
larger limits on the length of a directory entry's
name, but many old systems are still in use. Sys-
tems with shorter limits also exist, but news
software on such systems has had to deal with the
problem already, since there are several
widespread newsgroups with 14-character components
in their names. Implementors are warned that it
is intended that the successor to this Draft will
increase the 14-character limit, and are urged to
fix their software to handle longer names grace-
fully (if such fixes are necessary, given the
intended domain of application of the particular
software).
NOTE: The requirement that the first character of
a name be a letter accommodates existing software
which assumes it can tell the difference between a
newsgroup name and other possible syntactic enti-
ties by inspecting the first character. Similar
considerations motivate excluding "+", "-", and
"_" from coming first in a component, and the
preference for components that do not begin with
digits. The "all" sequence is used as a wildcard
symbol in much existing software, and the "ctl"
sequence was involved in an obsolete historical
mechanism for marking control messages, so they
are best avoided.
NOTE: Possibly newsgroup names should have been
case-insensitive, but all existing software treats
them as case-sensitive. (RFC 977 [rrr] claims
that they are case-insensitive in NNTP, but exist-
ing implementations are believed to ignore this.)
The simplest solution is just to ban use of upper-
case letters, since no widespread newsgroup name
uses them anyway; this avoids any possibility of
confusion.
NOTE: The syntax has the disadvantage of contain-
ing no white space, making it impossible to con-
tinue a Newsgroups header across several lines.
Implementors of relayers and reading agents are
warned that it is intended that the successor to
this Draft will change the definition of ng-delim
to:
ng-delim = "," [ space ]
and are urged to fix their software to handle
(i.e., ignore) white space following the commas.
Meanwhile, posters must avoid inserting such space
(despite the natural-language convention which
permits it) and posting agents should strip it
out.
NOTE: Encoded words as components are somewhat
problematic, but are clearly desirable for use in
non-English-speaking nations. They are not sub-
ject to the 14-character limit, and this (plus the
possibility of "/" within them) may require spe-
cial handling in news software.
Encoded words are allowed in newsgroup names ONLY where non-
ASCII characters are necessary to the name, and must use the
"b" encoding [rrr] and the first suitable character set in
the MIME order of preferred character sets [rrr].
NOTE: Since the newsgroup name is the encoded
form, NOT the underlying non-ASCII form, there is
room for terrible confusion here if the choice of
encoding for a particular name is not fully stan-
dardized.
Posters SHOULD use only the names of existing newsgroups in
the Newsgroups header, because newsgroups are NOT created
simply by being posted to. However, it is legitimate to
cross-post to newsgroup(s) which do not exist on the posting
agent's host, provided that at least one of the newsgroups
DOES exist there, and followup agents MUST accept this
(posting agents MAY accept it, but SHOULD at least alert the
poster to the situation and request confirmation). Relayers
MUST not rewrite Newsgroups headers in any way, even if some
or all of the newsgroups do not exist on the relayer's host.
NOTE: Early experience with news software that
created newsgroups when they were mentioned in a
Newsgroups header was thoroughly negative: posters
frequently mistype newsgroup names.
NOTE: While it is legitimate for some of an arti-
cle's newsgroups not to exist on the host where it
is posted, this IS a rather unusual situation
except in followups (which should go to all news-
groups the precursor was posted to, even if not
all of them reach the site where the followup is
being posted).
NOTE: Rewriting Newsgroups headers to strip
locally-unknown newsgroups is superficially
attractive. However, early experience with
exactly that policy was thoroughly negative: news
propagation is more redundant and much less
orderly than many people imagine, and in particu-
lar it is not unheard-of for the (sometimes)
fastest path between two (say) U of Toronto sites
to pass outside U of Toronto... in which case
newsgroup stripping can cause incomplete propaga-
tion. Having an article's set of newsgroups
change as it propagates can also result in fol-
lowups not achieving the same propagation as the
original. It's been tried; it's more trouble than
it's worth; don't do it.
NOTE: In particular, newsgroup stripping superfi-
cially looks like a solution to the problem of
duplicate regional newsgroup names. For example,
both University of Toronto and University of Texas
have "ut.general" newsgroups, and material cross-
posted to that name and a global newsgroup appears
in both universities' local newsgroups. However,
the side effects of stripping are sufficiently
unacceptable to disqualify it for this purpose.
Don't do it.
Cross-posting an article to several relevant newsgroups is
far superior to posting separate articles with duplicated
content to each newsgroup, because reading agents can detect
the situation and show the article to a reader only once.
Posters SHOULD cross-post rather than duplicate-post.
NOTE: On the other hand, cross-posting to a large
number of newsgroups usually indicates that the
poster has not thought about his audience; arti-
cles are rarely pertinent to more than (say) half
a dozen newsgroups. Posting agents might wish to
request confirmation when the number of newsgroups
exceeds (say) five in the presence of a Followup-
To header, or (say) two in the absence of such a
header.
NOTE: One problem with cross-postings is what to
do with an article cross-posted to a set of news-
groups including both moderated and unmoderated
ones. Posters tend to expect such an article to
show up immediately in the unmoderated newsgroups,
especially if they do not realize that one or more
of the newsgroups is moderated. However, since it
is not possible for a moderator to retroactively
add an already-posted article to a moderated news-
group, the only correct action is to mail such an
article to one (and only one) of the moderators
for action. It is probably best for the posting
agent to detect this situation and ask the poster
what action is preferred. The acceptable choices
are to alter the newsgroup list or to mail to a
moderator of the poster's choice; the posting
agent should NOT offer duplicate-posting as an
easy-to-request option (if only because many mod-
erators will reject a submission that has already
been posted to unmoderated newsgroups).
NOTE: An article cross-posted to multiple moder-
ated newsgroups really should have approval from
all the moderators involved. In practice, the
only straightforward way to do this is to send the
article to one of them and have him consult the
others.
A newsgroup SHOULD not appear more than once in the News-
groups header.
Newsgroup names having only one component are reserved for
newsgroups whose propagation is restricted to a single host
(or the administrative equivalent). It is inadvisable to
name a newsgroup "poster" because that word has special
meaning in the Followup-To header (see section 6.1). The
names "control" and "junk" are frequently used for pseudo-
newsgroups internal to relayer implementations, and hence
are also best avoided.
NOTE: Beware of the duplicate-regional-newsgroup-
names problem mentioned above. In particular,
there are many, many hosts with a newsgroup named
"general", and some surprising things show up in
such newsgroups when people cross-post. It is
probably better to use multi-component names,
which are less likely to be duplicated. Fred's
Widget House should use "fwh.general" rather than
just "general" as its in-house general-topics
newsgroup.
It is conventional to reserve newsgroup names beginning with
"to." for test messages sent on an essentially point-to-
point basis (see also the ihave/sendme protocol described in
section 7.2); newsgroup names beginning with "to." SHOULD
not be used for any other purpose. The second (and possibly
later) components of such a name should, together, comprise
the relayer name (see section 5.6) of a relayer. The news-
group exists only at the named relayer and its neighbors.
The neighbors all pass that newsgroup to the named relayer,
while the named relayer does not pass it to anyone.
The order of newsgroup names in the Newsgroups header is not
significant.