W3C home > Mailing lists > Public > uri@w3.org > August 2000

Re: Colons in URIs (rfc2396) for Universal Media URNs in URLs

From: Michael Mealling <michael@bailey.dscga.com>
Date: Fri, 18 Aug 2000 17:20:17 -0400
To: "Aaron E. Walsh" <aaron@mantiscorp.com>
Cc: uri@w3.org
Message-ID: <20000818172017.H5933@bailey.dscga.com>
On Fri, Aug 18, 2000 at 05:07:25PM -0400, Aaron E. Walsh wrote:
> I wonder if un-escaped colons are legal in the path portion of a URL so
> long as they're not in the scheme or domain? For example:

According to 2396 and my personal experience its legal. From the ABNF:

absoluteURI   = scheme ":" ( hier_part | opaque_part )
hier_part     = ( net_path | abs_path ) [ "?" query ]
abs_path      = "/"  path_segments
path_segments = segment *( "/" segment )
segment       = *pchar *( ";" param )
pchar         = unreserved | escaped |
                      ":" | "@" | "&" | "=" | "+" | "$" | ","

Which means that pchar says that an unencoded ':' is fine in
the path segment...

> http://www.web3dmedia.com/urn:web3d:media:/textures/nature/grass_1.jpg
> http://www.officetowers.com/urn:web3d:media:/textures/nature/rocks_3.jpg

Yep. I've seen that used before. The PDI URN space uses it...

> I ask because our Web3D Universal Media Working Group uses URNs for
> media referencing, which we'd like to extend to single URL environments
> such as standard HTML browsers and authoring tools (our use of URNs is
> based on the VRML97 ISO standard, which supports multiple URLs/URNs).
> The two URLs above show how we might embed a URN into a URL so that the
> media can be resolved via http (over the net) by products that don't
> understand Universal Media (just like a normal URL) while also giving
> products that understand our system what they need to know in order to
> fetch the media from the user's local system (the URN identifier
> "urn:web3d:media:" is the key; this tells Universal Media products that
> a piece of media is likely be be locally resident and so they'll attempt
> to resolve it locally first before trying the Web).
> I chair the Universal Media Working within the Web3D Consortium, and I'd
> like to extend our media system to URL/URI environments *without*
> conflicting with standard use of URIs/URLs. If you'd like some
> background on our work before commenting please feel free to visit our
> site at:
>   http://www.web3dmedia.com/UniversalMedia/
> To see how we deal with URNs, you can read our recommended practice:
>  http://www.web3dmedia.com/UniversalMedia/course/
>   see "VRML, URNs and Universal Media Recommended Practice Proposal"
> Below my signature is a message I recently sent to our group regarding
> using colons in URLs so that our URNs can be used by a wider audience.
> I've since read rfc2396 again and would like to know if it's possible to
> include colons in URLs without escaping them, like these:
> http://www.web3dmedia.com/urn:web3d:media:/textures/nature/grass_1.jpg
> http://www.officetowers.com/urn:web3d:media:/textures/nature/rocks_3.jpg
> Is this legal so long at the colon appears in the path (as above) and
> not in the scheme or domain?

From my reading, yes...

BTW, now that there is a URN registration process would it be to much
trouble to have this one registered? It just needs a short RFC on what
the space is and how its managed. See RFC 2611....


Michael Mealling	|      Vote Libertarian!       | www.rwhois.net/michael
Sr. Research Engineer   |   www.ga.lp.org/gwinnett     | ICQ#:         14198821
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Received on Friday, 18 August 2000 17:30:38 UTC

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