usefor-article-07 May 2002
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4.2.4. Comments
Strings of characters which are treated as comments may be included
in headers wherever the syntactic element CFWS occurs. They consist
of characters enclosed in parentheses. Comments may be nested.
NOTE: Although CFWS occurs wherever whitespace is allowed in
almost all headers, there are exceptions where only FWS is
permitted (hence folding but no comments). Notably, this happens
in the case of the Newsgroups-, Distribution-, Path- and
Followup-To-headers, and within the Date-header except right at
the end.
A comment is normally used to provide some human readable
informational text, except at the end of an address which contains no
phrase, as in
fred@foo.bar.example (Fred Bloggs)
as opposed to
"Fred Bloggs" <fred@foo.bar.example> .
The former is a deprecated, but commonly encountered, usage and
reading agents SHOULD take special note of such comments as
indicating the name of the person whose address it is. In all other
situations a comment is semantically interpreted as a single SP.
Since a comment is allowed to contain FWS, folding is permitted
within it as well as immediately preceding and immediately following
it. Also note that, since quoted-pair is allowed in a comment, the
parenthesis and backslash characters may appear in a comment so long
as they appear as a quoted-pair. Semantically, the enclosing
parentheses are not part of the content of the comment; the content
is what is contained between the two parentheses.
Since comments have not hitherto been permitted in news articles,
except in a few specified places, posters and posting-agents SHOULD
NOT insert them except in those places, namely following addresses in
From and similar headers, and to indicate the name of the timezone in
Date-headers. However, compliant software MUST accept them in all
places where they are syntactically allowed.
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#Diff to first older
--- ../usefor-article-06/Comments.out November 2001
+++ ../usefor-article-07/Comments.out May 2002
@@ -1,10 +1,15 @@
4.2.4. Comments
Strings of characters which are treated as comments may be included
- in header-contents wherever the syntactic element CFWS occurs. They
- consist of characters enclosed in parentheses. Such strings are
- considered comments so long as they do not appear within a quoted-
- string. Comments may be nested.
+ in headers wherever the syntactic element CFWS occurs. They consist
+ of characters enclosed in parentheses. Comments may be nested.
+
+ NOTE: Although CFWS occurs wherever whitespace is allowed in
+ almost all headers, there are exceptions where only FWS is
+ permitted (hence folding but no comments). Notably, this happens
+ in the case of the Newsgroups-, Distribution-, Path- and
+ Followup-To-headers, and within the Date-header except right at
+ the end.
A comment is normally used to provide some human readable
informational text, except at the end of an address which contains no
@@ -22,13 +27,13 @@
it. Also note that, since quoted-pair is allowed in a comment, the
parenthesis and backslash characters may appear in a comment so long
as they appear as a quoted-pair. Semantically, the enclosing
- parentheses are not part of the comment content; the content is what
- is contained between the two parentheses.
+ parentheses are not part of the content of the comment; the content
+ is what is contained between the two parentheses.
Since comments have not hitherto been permitted in news articles,
except in a few specified places, posters and posting-agents SHOULD
NOT insert them except in those places, namely following addresses in
From and similar headers, and to indicate the name of the timezone in
- Date headers. However, compliant software MUST accept them in all
+ Date-headers. However, compliant software MUST accept them in all
places where they are syntactically allowed.