Re: Relative URI in 2445 ?

[John Stracke <jstracke@xxxxxxxxxxx>]

Olivier Gutknecht wrote:

> A simple scenario could be a ics file with an external attachment 
> expressed as a file: URI then transferred (with the attachment) to a 
> FTP server. Using a relative link here could keep the resource 
> accessible without modification of the original iCalendar data. The 
> problem is that we don't have an explicit notion of a base URI in 
> iCalendar. so that's probably invalid or left to the interpretation of 
> the CUA ?

I would think so.  It's analogous to the case of HTML: HTML permits 
relative links, but you have to be careful with them when transferring 
data around.  If you mail somebody a page that you see via an http: URL, 
relative links in the HTML will be invalid unless your MUA either 
rewrites them or (more commonly) adds a <base> tag.  Similarly, a CUA 
that composes iCalendar with relative URLs has to rewrite those URLs 
when it sends the iCalendar to any other CUA.

As a rule of thumb, I would say that relative URLs are highly unlikely 
to work in most iCalendar scenarios.  They work on a local drive; but 
very few applications store iCalendar in local files (the only exception 
I know of is Evolution).  They work on an HTTP server; but the only app 
I know of that stores iCalendar via HTTP is Outlook/Exchange, and that's 
a private HTTP server whose URLs are not likely to be visible to the 
iCalendar recipient.

If you have a scenario where it's useful to store iCalendar in a local 
file (despite the performance problems of searching such a store), I'd 
say you need to assume that URLs to anything outside the iCalendar store 
will break when you send the iCalendar to anybody else.

Personally, I don't think I'd care for a CUA that stored attachments via 
file: URLs pointing to random places on my hard drive; it reminds me 
strongly of Eudora, which used to (still does?) strip attachments off of 
incoming messages and dump them in J. Random Folder.  That was always a 
pain; I much prefer more modern MUAs, which leave the attachments in the 
messages and parse them out at render time.

--
/===========================================================\
|John Stracke      |jstracke@xxxxxxxxxxx                    |
|Principal Engineer|http://www.centive.com                  |
|Centive           |My opinions are my own.                 |
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|"What we have here is a failure to assimilate." --Cool Hand|
|Locutius                                                   |
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