usefor-article-08 August 2002
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4.2.2. MIME-style Parameters
The possibility of allowing MIME-style parameters (whether header-
specific ones or generic other-parameters) to appear in virtually all
headers is provided mainly for the purpose of allowing future
extensions to existing headers, since only a very few specific
parameters are defined in this standard. Observe that such parameters
do not, in general, occur in headers defined in other standards,
except for the MIME standards [RFC 2045] et seq. and their
extensions.
Other-parameters (whether those defined elsewhere or experimental
parameters whose attribute is an x-token) MAY be used, where the
syntax so allows, in any of the headers defined in this standard or
its extensions except that, at present, they SHOULD NOT be used in
headers in widespread use prior to the introduction of this standard
(this restriction is likely to be removed in a future version of this
standard). Nevertheless, compliant software MUST accept such
parameters where required by this standard (ignoring them if their
meaning is unknown) and SHOULD accept (and ignore) them in all
structured headers wherever defined.
NOTE: The syntax does not permit other-parameters in
unstructured headers (where they are unnecessary) or in certain
headers (notably the From-, Reply-To-, Mail-Copies-To- and
Complaints-To-headers) containing address-lists or mailbox-lists
(so that agents can simply replace the header-name by "To" or
"Cc" to obtain a header immediately suitable for sending Email,
and also so as to avoid some minor parsing problems with
<address>es).
Each header-specific MIME-style parameter introduced in this standard
is described by specifying
(a) the token to be used in its attribute, and
(b) the syntax rule(s) defining the object(s) permitted in its
value.
If a value object is not of the syntactic form of a token, it MUST
(and otherwise MAY) be encapsulated in a quoted-string (see 2.4.3).
Observe that the syntax of a parameter also allows additional WSP,
folding and comments.
The semantics of a parameter is always to associate the token in its
attribute with the object represented by the token, or the semantic
value (2.4.3) of the quoted-string, contained in its value.
For example, the posting-sender-parameter (6.19) is defined to be
<a parameter with attribute "sender" and value some sender-value>
where
sender-value = mailbox / "verified"
A valid posting-sender-parameter would be
sender = "\"Joe D. Bloggs\" <jdbloggs@bloggs.example>" (authinfo)
The comment (syntactically part of the quoted-string) is irrelevant.
The actual mailbox (to be used, for example, if email is to be sent
to the sender) is
"Joe D. Bloggs" <jdbloggs@bloggs.example>
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#Diff to first older
--- ../usefor-article-07/MIME-style_Parameters.out May 2002
+++ ../usefor-article-08/MIME-style_Parameters.out August 2002
@@ -27,10 +27,10 @@
(so that agents can simply replace the header-name by "To" or
"Cc" to obtain a header immediately suitable for sending Email,
and also so as to avoid some minor parsing problems with
- addresses).
+ <address>es).
- Each header-specific parameter introduced in this standard is
- described by specifying
+ Each header-specific MIME-style parameter introduced in this standard
+ is described by specifying
(a) the token to be used in its attribute, and
(b) the syntax rule(s) defining the object(s) permitted in its
value.
@@ -48,9 +48,9 @@
where
sender-value = mailbox / "verified"
A valid posting-sender-parameter would be
- sender = "\"Joe D. Bloggs\" <jdbloggs@example.com>" (authinfo)
+ sender = "\"Joe D. Bloggs\" <jdbloggs@bloggs.example>" (authinfo)
The comment (syntactically part of the quoted-string) is irrelevant.
The actual mailbox (to be used, for example, if email is to be sent
to the sender) is
- "Joe D. Bloggs" <jdbloggs@example.com>
+ "Joe D. Bloggs" <jdbloggs@bloggs.example>