usefor-article-13 May 2004

2.4.2.  Syntax copied from other standards

   The following syntactic forms for characters, atoms and folding,
   taken from [RFC 2234] or from [RFC 2822] and adapted to incorporate
   variations introduced in [RFC 2047], are repeated here for
   convenience only:

      ALPHA         = %x41-5A /          ; A-Z
            %x61-7A            ; a-z
      CR            = %x0D               ; carriage return
      CRLF          = CR LF
      DIGIT         = %x30-39            ; 0-9
      HTAB          = %x09               ; horizontal tab
      LF            = %x0A               ; line feed
      SP            = %x20               ; space
      NO-WS-CTL     = %d1-8 /            ; US-ASCII control characters
            %d11 /             ; which do not include the
            %d12 /             ; carriage return, line feed,
            %d14-31 /          ; and whitespace characters
            %d127
      specials      = "(" / ")" /        ; Special characters used in
            "<" / ">" /        ; other parts of the syntax
            "[" / "]" /
            ":" / ";" /
            "@" / "\" /
            "," / "." /
            DQUOTE
      WSP           = SP / HTAB          ; whitespace characters
      FWS           = ([*WSP CRLF] 1*WSP); folding whitespace
      ccontent      = ctext / quoted-pair / comment / encoded-word
      comment       = "(" *([FWS] ccontent) [FWS] ")"
      CFWS          = *([FWS] comment) ( ([FWS] comment) / FWS )
      DQUOTE        = %d34               ; quote mark
      quoted-pair   = "\" text
      atext         = ALPHA / DIGIT /
            "!" / "#" /        ; Any US-ASCII character except
            "$" / "%" /        ; controls, SP, and specials.
            "&" / "'" /        ; Used for atoms
            "*" / "+" /
            "-" / "/" /
            "=" / "?" /
            "^" / "_" /
            "`" / "{" /
            "|" / "}" /
            "~"
      atom          = [CFWS] 1*atext [CFWS]
      dot-atom      = [CFWS] dot-atom-text [CFWS]
      dot-atom-text = 1*atext *( "." 1*atext )
      qcontent      = qtext / quoted-pair
      quoted-string = [CFWS] DQUOTE
               *( [FWS] qcontent ) [FWS]
               DQUOTE [CFWS]
      word          = atom / quoted-string

        NOTE: Following [RFC 2234], literal text included in the syntax
        is to be regarded as case-insensitive.  However, in
        contradistinction to [RFC 2822], the Netnews protocols are
        sensitive to case in some instances (as in newsgroup-names, some
        header parameters, etc.). Care has been taken to indicate this
        explicitly where required.

   As in [RFC 2822], where any quoted-pair appears it is to be
   interpreted as its text character alone. That is to say, the "\"
   character that appears as part of a quoted-pair is semantically
   "invisible".

   Again, as in [RFC 2822], strings of characters that include
   characters not syntactically allowed in some particular context may
   be incorporated into a quoted-string by "encapsulating" them between
   quote (DQUOTE, US-ASCII 34) characters, prefixing every quote and
   backslash character (and possibly other characters too) with a "\" so
   as to form a quoted-pair, and possibly introducing folding by
   prefixing some WSP with CRLF.

   The semantic value of a quoted-string (i.e. the result of reversing
   the encapsulation) is a string of characters which includes neither
   the optional CFWS outside of the quote characters, nor the quote
   characters themselves, nor any CRLF contained within any FWS between
   the two quote characters, nor the "\" which introduces any quoted-
   pair.

   The following basic forms are taken from [RFC 2045] and [RFC 2231]
   (having regard to [RFC Errata]), adapted to use the folding syntax
   from [RFC 2822]:

      charset       = <registered character set name>
                               ;  [RFC 2978]
      language      = <registered language tag>
                               ;  [RFC 3066]
      encoded-word  = "=?" charset ["*" language] "?" encoding
               "?" encoded-text "?="
      parameter     = regular-parameter / extended-parameter
      regular-parameter       = [CFWS] regular-parameter-name [CFWS]
               "=" value
      regular-parameter-name  = attribute [section]
      attribute     = 1*attribute-char
      attribute-char= <any (US-ASCII) CHAR except SPACE, CTLs,
               "*", "'", "%", or tspecials>
      tspecials     = "(" / ")" / "<" / ">" / "@" /
            "," / ";" / ":" / "\" / DQUOTE /
            "/" / "[" / "]" / "?" / "="
      extended-parameter
          = ( [CFWS] extended-initial-name [CFWS]
               "=" extended-initial-value ) /
            ( [CFWS] extended-other-names [CFWS]
               "=" extended-other-values )
      value         = [CFWS] token [CFWS] / quoted-string
      token         = 1*<any (US-ASCII) CHAR except SP, CTLs,
               or tspecials>

   For the purposes of section 5 of [RFC 2047] all headers (4.1) defined
   in this standard are to be considered as "extension message header
   fields" (insofar as they are not already so considered under the
   existing Email standards), permitting the use of [RFC 2047] encodings
   within any unstructured header, or within any comment or phrase
   permitted within any structured header.

   The syntax of encoded-text and of encoding can be found in [RFC
   2047], and there are restrictions on the characters that may occur
   within an encoded-text, depending on its context. There are also
   restrictions on the overall length of an encoded-word and of headers
   containing encoded-words and requirements for encoded-words to have
   FWS on either side of them in most contexts. All these restrictions
   and requirements MUST be observed.

--- ../usefor-article-12/Syntax_copied_from_other_standards.out          November 2003
+++ ../usefor-article-13/Syntax_copied_from_other_standards.out          May 2004