ietf-822
[Top] [All Lists]

The TEXT/HTML Content Type in e-mail

1995-11-02 07:52:22
Harald T. Alvestrand has asked me to write something about this.

After thinking much about this, and considering both my own earlier
proposal and Ed Levinsons counterproposal, I have concluded that
a third alternative would be more suitable than our earlier
alternatives. The third alternative is shown by the following
example:

.... main message heading ...
Content-Type: Multipart/related
   ... Content-part 1 ...
   Content-Type: Multipart/alternative
      ... Content-part 1.1
      Content-Type: Text/plain
      ... plain text version for those who cannot read HTML ...
      ... Content-part 1.2
      Content-Type: Text/HTML
      ... HTML version of the same message, which many contain ...
      ... external file references, as shown in the example ...
      ... which follows on the next line ...
      <IMG SRC=HTTP://www.dsv.su.se/picture.GIF>
   ... Content-part 2 ...
   Content-Type: Image/GIF
   Content-Location: HTTP://www.dsv.su.se/picture.GIF
   ... the GIF picture

Here is a comparison of the new notation suggested above for some
common combinations of user software:

User software             New notation using        Notation using CIM URL-s
                          Content-Location

Mail system which has no  The user can manually     The user will have to
knowledge of the          save the Text/HTML        modify the HTML text
Text/HTML Content-Type    content in a file, and    and replace the CIM URL-
                          open and view it with an  s with file references.
                          ordinary Web browser.

Mail system which uses    The user can view the     Will not work unless the
an ordinary Web browser   message, including        mail system goes into
as a helper application   pictures, with no         the text and changes the
to view Text/HTML         problems. (The pictures   CIM URL-s to something
Contents                  will actually be          else.
                          downloaded from a remote
                          WWW server, but that is
                          normal WWW client
                          behaviour.)

Mail system which uses a  The user can still use    Either the mail system
proxy HTML server         an ordinary Web browser,  will have to modify the
                          the proxy server will     CIM URL-s, or the Web
                          recognize that it has     browser must recognize
                          the picture locally and   CIM URL-s and know how
                          not retrieve it from its  to retrieve them from
                          remote location.          the mail system.

Mail system with built-   No problem                No problem
in Web browser.

Thus, in the first three of the four cases discussed above, my new
proposed format is easier to implement and use than the earlier proposals
using CID-s which I and Ed Levinson wrote. I am not against CID-s and
MID-s as a long-term proposal, but in the short term, my new proposal
makes things simpler in three of the four cases.

(Note: A similar idea was put forward by Ron Croonenberg in a message
two weeks ago.)

----------------------------------------------------------------------
Jacob Palme <jpalme(_at_)dsv(_dot_)su(_dot_)se> (Stockholm University and KTH)
for more info see URL: http://www.dsv.su.se/~jpalme