Relative URI in 2445 ?

[Olivier Gutknecht <olivierg@xxxxxxxxx>]

Hi

Do we accept relative links in URI values in RFC 2445, for instance in 
ATTACH ?

The specification says:
	Purpose: This value type is used to identify values that contain a 
uniform resource 	identifier (URI) type of reference to the property 
value.
	Formal Definition: The data type is defined by the following    
notation:
	uri        = <As defined by any IETF RFC>

	Description: This data type might be used to reference binary 
information, for values that are large, or otherwise undesirable to 
include directly in the iCalendar object. The URI value formats in RFC 
1738, RFC 2111 and any other IETF registered value format can be 
specified. Any IANA registered URI format can be used. These include, 
but are    not limited to, those defined in RFC 1738 and RFC 2111.

1738 only covers relative links with the following definition: "In some 
cases, URLs are used to locate resources that contain pointers to other 
resources. In some cases, those pointers are represented as relative 
links where the expression of the location of    the second resource is 
in terms of "in the same place as this one    except with the following 
relative path". Relative links are not described in this document. 
However, the use of relative links depends on the original URL 
containing a hierarchical structure against which the relative link is 
based. Some URL schemes (such as the ftp, http, and file schemes) 
contain names that can be considered hierarchical; the components of 
the hierarchy are separated by "/". "

My question is: -if- the iCalendar data is stored and referenced 
through a scheme which is compatible with relative linking (i.e. an ics 
file on a filesystem file:/home/olg/mycal/ol.ics, or accessed through a 
http://foobar.com/cals/ol.ics or ftp url, is it correct iCalendar to 
use a relative URI in an attach property ?
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 ?

Ol.