[caldeveloper-l] Question about description ALTREP

Tue Mar 13 10:13:40 PDT 2018

Hi,

I believe the text you include comes from  https://tools.ietf.org/html/rfc5545#section-3.2.1

This section of RFC2447 (iMIP)  should help.  Essentially, the example is expected to be used in the context of a single MIME message, and the URI with prefix CID: is expected to appear in the DESCRIPTION property of a text/calendar body part and reference a completely separate body part inside the same MIME message.  More generally, I expect that an HTTPS URI could be used to provide a link to an alternative representation on the internet.

https://tools.ietf.org/html/rfc2447#section-5.1
5.1 Use of Content and Message IDs

   The [iCAL] specification makes frequent use of the URI for data types
   in properties such as "DESCRIPTION", "ATTACH", "CONTACT" and others.
   Two forms of URIs are Message ID (MID) and Content ID (CID). These
   are defined in [RFC-2111]. Although [RFC-2111] allows referencing
   messages or MIME body parts in other MIME entities or stores, it is
   strongly recommended that iMIP implementations include all referenced
   messages and body parts in a single MIME entity. Simply put, if an
   iCalendar object contains CID or MID references to other messages or
   body parts, implementations should ensure that these messages and/or
   body parts are transmitted with the iCalendar object. If they are not
   there is no guarantee that the receiving "CU" will have the access or
   the authorization to view those objects.

Regards,
Gren Elliot
Lead Engineer - Server
Zimbra - A Synacor Product
Office 408, Euston House, 24 Eversholt St, London, NW1 1AD, United Kingdom
gren.elliot at synacor.com

From: Tim Hare <timhare at comcast.net>
Reply: Tim Hare <timhare at comcast.net>
Date: 13 March 2018 at 16:09:51
To: 'caldeveloper-l mailing list' <caldeveloper-l at lists.calconnect.org>
Subject:  [caldeveloper-l] Question about description ALTREP  

Cross-posted to calsify but no response so far.

In the RFC section on the ALTREP property for the DESCRIPTION component I see an example of using ALTREP to provide HTML in a description (for our internal application, because we use Outlook for calendaring, we have been using Microsoft’s X-ALT-DESC, but I’d like to use the new ALTREP).  What’s not clear from the example below, is whether the content part beginning with Content-Type:  is positioned in the data within the DESCRIPTION component,  or should be positioned _after_  the END:VCALENDAR statement (since the BEGIN:VCALENDAR / END:VCALENDAR pair is assumed to be Content-Type: text/calendar.  I guess that’s really two questions:   

1.  in an .ics file, where does the ALTREP go if you are using content identifier – in the DESCRIPTION or after the END:VCALENDAR?
2.  Can there be a Content-Type: text/Calendar and Content-Id:  in the .ics file before the BEGIN:VCALENDAR

For myself, the questions specifically relate to the use case where we create an .ics file that others may subscribe to;  other use cases such as mailing a calendar might have other answers.

Thanks
Tim Hare
Interested Bystander, Non-Inc.

>   Example:
> 

>       DESCRIPTION;ALTREP="CID:part3.msg.970415T083000 at example.com":

>        Project XYZ Review Meeting will include the following agenda

>         items: (a) Market Overview\, (b) Finances\, (c) Project Man

>         agement

> 

>      The "ALTREP" property parameter value might point to a "text/html"

>      content portion.

> 

>       Content-Type:text/html

>       Content-Id:<part3.msg.970415T083000 at example.com>

> 

>       <html>

>         <head>

>          <title></title>

>         </head>

>         <body>

>           <p>

>             <b>Project XYZ Review Meeting</b> will include

>             the following agenda items:

>             <ol>

>               <li>Market Overview</li>

>               <li>Finances</li>

>               <li>Project Management</li>

>             </ol>

>           </p>

>         </body>

>       </html>

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