(2)   BNF describing the overall structure of MIME object
          headers has been added. This is a documentation change
          only -- the underlying syntax has not changed in any
          way.

    (3)   The specific BNF for the seven media types in MIME has
          been removed.  This BNF was incorrect, incomplete, amd
          inconsistent with the type-indendependent BNF.  And
          since the type-independent BNF already fully specifies
          the syntax of the various MIME headers, the type-
          specific BNF was, in the final analysis, completely
          unnecessary and caused more problems than it solved.

    (4)   The more specific "US-ASCII" character set name has
          replaced the use of the informal term ASCII in many
          parts of these documents.

    (5)   The informal concept of a primary subtype has been
          removed.

    (6)   The term "object" was being used inconsistently.  The
          definition of this term has been clarified, along with
          the related terms "body", "body part", and "entity",
          and usage has been corrected where appropriate.

    (7)   The BNF for the multipart media type has been
          rearranged to make it clear that the CRLF preceeding
          the boundary marker is actually part of the marker
          itself rather than the preceeding body part.

    (8)   The prose and BNF describing the multipart media type
          have been changed to make it clear that the body parts
          within a multipart object MUST NOT contain any lines
          beginning with the boundary parameter string.

    (9)   In the rules on reassembling "message/partial" MIME
          entities, "Subject" is added to the list of headers to
          take from the inner message, and the example is
          modified to clarify this point.

    (10)  "Message/partial" fragmenters are restricted to
          splitting MIME objects only at line boundaries.

    (11)  In the discussion of the application/postscript type,
          an additional paragraph has been added warning about
          possible interoperability problems caused by embedding
          of binary data inside a PostScript MIME entity.





 
RFC 2049                    MIME Conformance               November 1996


    (12)  Added a clarifying note to the basic syntax rules for
          the Content-Type header field to make it clear that the
          following two forms:

            Content-type: text/plain; charset=us-ascii (comment)

            Content-type: text/plain; charset="us-ascii"

          are completely equivalent.

    (13)  The following sentence has been removed from the
          discussion of the MIME-Version header: "However,
          conformant software is encouraged to check the version
          number and at least warn the user if an unrecognized
          MIME-version is encountered."

    (14)  A typo was fixed that said "application/external-body"
          instead of "message/external-body".

    (15)  The definition of a character set has been reorganized
          to make the requirements clearer.

    (16)  The definition of the "image/gif" media type has been
          moved to a separate document. This change was made
          because of potential conflicts with IETF rules
          governing the standardization of patented technology.

    (17)  The definitions of "7bit" and "8bit" have been
          tightened so that use of bare CR, LF can only be used
          as end-of-line sequences.  The document also no longer
          requires that NUL characters be preserved, which brings
          MIME into alignment with real-world implementations.

    (18)  The definition of canonical text in MIME has been
          tightened so that line breaks must be represented by a
          CRLF sequence.  CR and LF characters are not allowed
          outside of this usage.  The definition of quoted-
          printable encoding has been altered accordingly.

    (19)  The definition of the quoted-printable encoding now
          includes a number of suggestions for how quoted-
          printable encoders might best handle improperly encoded