[Playlist] Question on identifier content, URI and URN

[Kevin Marks]

On Aug 27, 2006, at 8:42 PM, Lucas Gonze wrote:
> We were concerned with enabling the http scheme to be used purely for 
> identifiers.  Let's say, for example, that there could be an 
> identifier "http://example.com/acdc/girlsgotrhythm" which was used to 
> signify a specific song, regardless of the address of any particular 
> instance of the song.  This identifier would be a mapping to the song 
> at a semantic level only, so that a different rip with different 
> settings would still match the same underlying composition and sound 
> recording.  It might still return something when dereferenced, like a 
> set of metadata about the song or an explanation of how it might be 
> used, it just wouldn't be dereferenceable to obtain a representation 
> of the song.
>
> For an example of such a URL in the real world, see 
> http://musicbrainz.org/track/7e1d6f5f-0ac3-4889-8b57-506a67b459fc.html 
> .
>
> In the olden days there were specific schemes designed for use this 
> way.   The urn scheme, for one.  :)  That has changed.  In recent 
> times many people have stopped thinking of the http scheme as being 
> restricted to locators; hence our need to distinguish at the XSPF 
> level between an http URI used as an identifier and an http URI used 
> as a locator.

The W3C TAG recently wrote a rather good paper on this very issue:

http://www.w3.org/2001/tag/doc/URNsAndRegistries-50.html

basically, http URLs are rather useful GUIDs. URNs are broadly worse.