The text/enriched MIME Content-type
RFC 1523

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Network Working Group                                      N. Borenstein
Request for Comments: 1523                                      Bellcore
Category: Informational                                   September 1993

                  The text/enriched MIME Content-type

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard.  Distribution of this memo is
   unlimited.

Abstract

   MIME [RFC-1341, RFC-1521] defines a format and general framework for
   the representation of a wide variety of data types in Internet mail.
   This document defines one particular type of MIME data, the
   text/enriched type, a refinement of the "text/richtext" type defined
   in RFC 1341.  The text/enriched MIME type is intended to facilitate
   the wider interoperation of simple enriched text across a wide
   variety of hardware and software platforms.

The Text/enriched MIME type

   In order to promote the wider interoperability of simple formatted
   text, this document defines an extremely simple subtype of the MIME
   content-type "text", the "text/enriched" subtype.  This subtype was
   designed to meet the following criteria:

         1.  The syntax must be extremely simple to parse, so that even
         teletype-oriented mail systems can easily strip away the
         formatting information and leave only the readable text.

         2.  The syntax must be extensible to allow for new formatting
         commands that are deemed essential for some application.

         3.  If the character set in use is ASCII or an 8- bit ASCII
         superset, then the raw form of the data must be readable enough
         to be largely unobjectionable in the event that it is displayed
         on the screen of the user of a non-MIME-conformant mail reader.

         4.  The capabilities must be extremely limited, to ensure that
         it can represent no more than is likely to be representable by
         the user's primary word processor.  While this limits what can
         be sent, it increases the likelihood that what is sent can be
         properly displayed.

Borenstein                                                      [Page 1]
RFC 1523           A text/enriched MIME Content-type      September 1993

   This document defines a new MIME content-type, "text/enriched".  The
   content-type line for this type may have one optional parameter, the
   "charset" parameter, with the same values permitted for the
   "text/plain" MIME content-type.

   The syntax of "text/enriched" is very simple.  It represents text in
   a single character set -- US-ASCII by default, although a different
   character set can be specified by the use of the "charset" parameter.
   (The semantics of text/enriched in non-ASCII character sets are
   discussed later in this document.)  All characters represent
   themselves, with the exception of the "<" character (ASCII 60), which
   is used to mark the beginning of a formatting command.  Formatting
   instructions consist of formatting commands surrounded by angle
   brackets ("<>", ASCII 60 and 62).  Each formatting command may be no
   more than 60 characters in length, all in US-ASCII, restricted to the
   alphanumeric and hyphen ("-") characters.  Formatting commands may be
   preceded by a solidus ("/", ASCII 47), making them negations, and
   such negations must always exist to balance the initial opening
   commands.  Thus, if the formatting command "<bold>" appears at some
   point, there must later be a "</bold>" to balance it.  (NOTE: The 60
   character limit on formatting commands does NOT include the "<", ">",
   or "/" characters that might be attached to such commands.)

   Formatting commands are always case-insensitive.  That is, "bold" and
   "BoLd" are equivalent in effect, if not in good taste.

   Beyond tokens delimited by "<" and ">", there are two other special
   processing rules.  First, a literal less-than sign ("<") can be
   represented by a sequence of two such characters, "<<".  Second, line
   breaks (CRLF pairs in standard network representation) are handled
   specially.  In particular, isolated CRLF pairs are translated into a
   single SPACE character.  Sequences of N consecutive CRLF pairs,
   however, are translated into N-1 actual line breaks.  This permits
   long lines of data to be represented in a natural- looking manner
   despite the frequency of line-wrapping in Internet mailers.  When
   preparing the data for mail transport, isolated line breaks should be
   inserted wherever necessary to keep each line shorter than 80
   characters.  When preparing such data for presentation to the user,
   isolated line breaks should be replaced by a single SPACE character,
   and N consecutive CRLF pairs should be presented to the user as N-1
   line breaks.

Borenstein                                                      [Page 2]
RFC 1523           A text/enriched MIME Content-type      September 1993