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Re: Registration of media type application/calendar+xml

2010-09-10 09:46:15
Hi Keith,

--On September 9, 2010 10:51:10 PM -0400 Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu> wrote:

An XML representation for iCalendar is vital if we are to keep iCalendar
relevant in the web-based world. The drive for this work comes from a
number of areas - in particular the smart grid effort sponsored by NIST
will make use of this as part of the standards suite they are defining.

Somebody needs to talk some sense into those people.  Defining another
calendar format will only harm interoperability.  It doesn't save any
calendar implementation from needing to implement another parser, because
if it wants to interoperate with existing products or be able to read old
events it's still going to have to support iCalendar and probably
vCalendar also.  So what's the _technical_ (not political) benefit from
doing this?

First of all look at the mess we have got into with contacts (see recent discussion on the vcarddav WG mailing list). There we now have vCard, PoCo, OpenSocial and some new thing the OMA is doing (and their are lots of private apis too). Yet vCard has been around for a long time - why didn't those other folks just use that or at least propose fixes or extension to vcard that would satisfy their issues? Well, certainly in the case of PoCo one clear requirement was for a simple web/browser based solution - so they designed JSON and XML representations.

The same mess could happen to iCalendar too. In fact there are already lots of examples of "private" apis using XML to represent calendar data, see e.g. Google GDATA. Plus I know of some public event services that uses their own custom XML format for event publishers to submit calendar data to them. In fact the initial impetus for this work did come from one such public events company that really wanted to use iCalendar rather than some home grown solution, but really wanted that as XML. Sure you can argue that they should be made to parse iCalendar format, but why should they have to write their own new parser when they already have reliable, efficient XML processing available.

Frankly the important thing here is the semantics of the iCalendar model, not the syntax. I want developers to only have to concentrate on getting the semantics right without worry too much about the syntax.

Now I can understand your concern about poor interoperability when it comes to having the two data formats. I think for the HTTP-based world (CalDAV, iSchedule, web-services) this is really not a big deal given the content negotiation options. For something like iMIP (iCalendar in email) it is a much bigger problem. Speaking for myself only, and not my co-authors, I think I would be OK with adding a statement that iMIP messages SHOULD NOT use the application/calendar+xml format, or at the very least require both text/calendar and application/calendar+xml in e.g. a multipart/alternative (though I would worry that the later would cause existing clients problems, and lead to message bloat).

IETF's job is to provide technical leadership, not to follow bad advice.
Instead of caving into them, what we need to do is publish a draft called
"Translating Everything into XML Considered Harmful".

Ah, yes. I seem to recall something similar for the use of HTTP - perhaps the author of RFC 3205 would like to author this new document too :-)


--
Cyrus Daboo

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