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Re: [dix] on the dix: URI scheme for DIX/SXIP

From: Tim Bray <tbray@textuality.com>
Date: Mon, 20 Mar 2006 07:42:57 -0800
To: Dick Hardt <dick@sxip.com>
Cc: Digital Identity Exchange <dix@ietf.org>, John Merrells <merrells@sxip.com>, Lisa Dusseault <lisa@osafoundation.org>, uri@w3.org
Message-id: <8024A864-1867-434B-98E2-FC244309280E@textuality.com>

On Mar 20, 2006, at 6:54 AM, Dick Hardt wrote:

> Agree that we need to make good use of scarce community resources.

On top of which, using an "http:" URI has the huge advantage that you  
can put something useful there that a human being can point their  
browser at and learn something about what this string means.

I'd advise those who are promoting the new URI scheme to check out  
the remarks about URI schemes in http://www.w3.org/TR/webarch/ and in  
particular http://www.w3.org/TR/webarch/#URI-scheme - when you are  
doing something that flies in the face of a SHOULD recommendation in  
the "Architecture of the World Wide Web", you need to have really  
thought it through.

> The reasoning behind introducing a new scheme was we need an escape  
> sequence for processing the name/value pairs and to differentiate  
> data from constants etc.. Anything starting with "dix:" is known to  
> be a constant. Anything else is not. :) -- one of the reasons for  
> this is that we want to be able to pass through name/value pairs  
> that a web application may be using to preserve state. We think the  
> likelihood that any existing app have strings that start with  
> "dix:/" to be, well, really really small.

You're saying that you need a reliable way to ascertain that this  
identifier contains name-value pairs that should be processed per  
DIX?  Can this be established by context?  Any other signaling  
mechanisms?

If not, then why are you buying into all the expectations and culture  
that go with using a URI, why not just use an opaque string or a  
chunk of XML or ";"-separated name-value pairs or whatever?  A URI is  
supposed to identify a resource, and a common expectation is that one  
way or another, you can use it to retrieve information.  If you avoid  
specifying one particular scheme, you leave the door open for  
different modes of information retrieval down the road.

> Does this make sense? Do you have a suggestion for another approach  
> that provides an escape mechanism and allows decentralized  
> property /capability extension?

In general, naming things with URIs is a good and Web-friendly thing  
to do; as you point out, the use of the authority field allows  
distributed authority over parts of the namespace.  In particular,  
HTTP URIs have a lot of advantages.

-Tim
Received on Monday, 20 March 2006 15:42:49 GMT

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