Subject: Re: [Uri-review] New icon URI scheme vs new URN namespace

From: Graham Klyne <[email-masked]>
Date: Tue, 18 May 2010 11:04:13 +0100

I just realized that I've fallen off the URI-review mailing list, so I missed 
some of this discussion as it happened.

Unfortunately, I think the discussion of URN "persistence" has somewhat 
distracted attention from the primary point of discussion:  what is the 
preferred form of URI for identifying an icon?

Three suggestions have been made:
1. new icon: scheme
2. http: URI with special domain
3. urn namespace

Approach 1 is clearly easy to implement, but IMO falls foul of the concern noted 
in RFC 4395 section 2.1 (http://tools.ietf.org/html/rfc4395#section-2.1): "New 
URI schemes SHOULD have clear utility to the broad Internet community, beyond 
that available with already registered URI schemes.".  I think this qualifies as 
an element of the guidance that has been requested.

Approach 2 is, prima facie, a preferred route for the web/W3C community's 
preference for using http: URIs (e.g. per 
http://www.w3.org/DesignIssues/LinkedData.html).  But in this case, I think it 
could be an inappropriate overloading of http: semantics, as the proposed icon: 
scheme explicitly defines retrieval semantics that are at variance with defined 
http: retrieval semantics.

I would suggest this application is an appropriate use for approach 3.  From a 
philosophical perspective, it broadly matches the goals of URNs.  From a 
practical implementation point of view, I think the implementation should be 
very little changed from an implementation of the proposed icon: scheme.

#g