W3C home > Mailing lists > Public > public-webid@w3.org > November 2012

Re: Hash vs Hashless URIs

From: Henry Story <henry.story@bblfish.net>
Date: Tue, 20 Nov 2012 15:11:40 +0100
Cc: Melvin Carvalho <melvincarvalho@gmail.com>, Kingsley Idehen <kidehen@openlinksw.com>, "public-webid@w3.org" <public-webid@w3.org>
Message-Id: <ADFBF89E-F4DF-4F9C-992F-7D3359E44243@bblfish.net>
To: Stéphane Corlosquet <scorlosquet@gmail.com>

On 20 Nov 2012, at 00:36, Stéphane Corlosquet <scorlosquet@gmail.com> wrote:

> I don't deny the fact that hash URIs have their advantages and I personally prefer them too for WebID, but I don't see the need to set that in stone wrt to WebID URIs. Like I said before, who knows what new mechanism will come out of the TAG or elsewhere 2 years down the road? Mandating hash URIs means that any kind of innovation in the realm of WebID will be impossible without breaking the spec.
> Can't we agree on the following compromise? => only use hash URIs in the non-nominative examples. This is leave for innovation down the road, in the meantime most people can follow the hash routes unless they prefer some other way.
> Does mandating "hash URIs only" provide any advantage in terms of implementing a WebID verifier? A verifier would still rely on HTTP to dereference the WebID URI, and follow any redirect if necessary. What are the advantages from a verifier standpoint? How does it make is simpler than just any kind of URI?

I think Tim Berners Lee had a number of objections on the of tracking 303 redirected URIs. He said it massively slowed down the Tabulator code.

It also makes our explanation more complex in the explanation in the spec.

As I see we all have consensus that #uri are WebIDs, and there is lack of consensus on whether 
303s non has uris should also be. The new principle has to be: wherever we can make things simpler we do so - as long as we don't close options further down. By defining WebIDs to be just #uris, we don't close options further down, and we leave it to other people who want to join to make their case when we go to W3C WG.

The idea is make it simple for people to join.

My problem with 303's vocabs such as foaf is that you don't know when a uri is defined in a document 
until you dereference each URI. For example each of


Are all defined by the 


but you don't know that until you have done an HTTP GET for each of those resources. 
This is important because understanding which document is defining a term, is key to
WebID-TLS authentication. A document that defines a term is making something close
to a necessarily true assertion, as you know from mathematics.

That means that even though you may already have fetched all the foaf definitions,
you still have to interact with the server to find out if you have the definitions. 

Notice the security hole that breaks up if you are not careful otherwise:

I create a WebID+ for </ppl/joe> 
this redirects to 


which describes ( and seems to define) also 

You can know imagine a server implementing WebID protocol badly that on the
authentication of /people/smith thinks it already has the definition for that WebID in

  There are a lot of things that end up needing explanation suddenly which we can
cut out by keeping our definition rigorously simple.


> Steph.
> On Mon, Nov 19, 2012 at 6:16 PM, Melvin Carvalho <melvincarvalho@gmail.com> wrote:
> On 19 November 2012 23:58, Kingsley Idehen <kidehen@openlinksw.com> wrote:
> All,
> To understand this old problem please read: http://www.w3.org/TR/2007/WD-cooluris-20071217/#hashuri .
> Important point to note, this matter ultimately becomes a permathread whenever a spec attempts to pick one style over the other.
> The solution to these kinds of problems stem back to biblical stories, such as the one illustrating the wisdom of Solomon re. splitting a disputed baby in half.
> HTTP URIs are "horses for course" compliant. It is always best to keep them that way when designing specs for HTTP based solutions.
> Thanks
> "Conclusion.
> Hash URIs should be preferred for rather small and stable sets of resources that evolve together. An ideal case are RDF Schema vocabularies and OWL ontologies, where the terms are often used together, and the number of terms is unlikely to grow much in the future.
> Hash URIs without content negotiation can be implemented by simply uploading static RDF files to a Web server, without any special server configuration. This makes them popular for quick-and-dirty RDF publication.
> 303 URIs should be used for large sets of data that are, or may grow, beyond the point where it is practical to serve all related resources in a single document.
> If in doubt, it's better to use the more flexible 303 URI approach.
> "
> Will try and digest this a bit more.  I may still be missing something but if you have a paradigm of one data item per page and call it #, like facebook do, I'm still trying to see the advantage of 303s.  As pointed out, facebook is not a small data set. 
> -- 
> Regards,
> Kingsley Idehen 
> Founder & CEO
> OpenLink Software
> Company Web: http://www.openlinksw.com
> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
> Twitter/Identi.ca handle: @kidehen
> Google+ Profile: https://plus.google.com/112399767740508618350/about
> LinkedIn Profile: http://www.linkedin.com/in/kidehen
> -- 
> Steph.

Social Web Architect

Received on Tuesday, 20 November 2012 14:12:30 UTC

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