W3C home > Mailing lists > Public > semantic-web@w3.org > June 2007

Re: What if an URI also is a URL

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 06 Jun 2007 21:29:22 +0200
To: "r.j.koppes" <rikkert@rikkertkoppes.com>
Cc: Tim Berners-Lee <timbl@w3.org>, semantic-web@w3.org, swick@w3.org
Message-ID: <29610.1181158162@ubuhebe>


"r.j.koppes" <rikkert@rikkertkoppes.com> writes:
> Then please read "look up" instead of "access", I am talking about 
> visiting http://www.example.com/mophor#me as a web page, following a 
> link with this as a reference or putting it in an address bar of a browser.
> 
> This action only identifies http://www.example.com/mophor as it is this 
> URL that makes the server return a 200.
> 
> The URI http://www.example.com/mophor#me is not identified as a resource 
> at this moment.
> 
> But what if I DO identify it, by means of an RDF triple stating that 
> this URI (http://www.example.com/mophor#me) defines me (by linking it to 
> my social security number or whatever)
> 
> As of what I understand, up till now there are no problems. 
> http://www.example.com/mophor is identified as being a web page, 
> http://www.example.com/mophor#me is identified as being me.
> 
> But if, on the web page http://www.example.com/mophor there is a section 
> with id "me", how do I refer to that particular section in the web page 
> in a RDF document (which might contain anything, even unrelated to me as 
> a person)? How do I make sure that the reader (machine / human) 
> interprets this reference as being a web location (fragment in web page) 
> instead of the thing, me.

This is a problem.  You've described it quite nicely.   Various
solutions have been proposed over the years.   I think the two leading
contenders are:

    1.  Don't Do That.   Don't have that "#me" anchor on that page.

    2.  Use a "303 See Other" redirect, based on content negotiation, so
        that when someone asks for "http://www.example.com/mophor" they
        get redirected to one of two other pages, based on the content
        type they ask for:
           text/html -> "http://www.example.com/mophor-text"
           application/rdf+xml -> "http://www.example.com/mophor-data"
        The RDF page would talk about 
	   "http://www.example.com/mophor#me" as you.
        The HTML page would have a "me" fragment, but the base URI of
        the page with that fragment would be interpreted AFTER the
        redirect, so it would have the URI:
           http://www.example.com/mophor-text#me

        (At least I think that's how it would work.  I haven't dug into
        this one in a while.)

For most people, Option 1 seems to suffice.  The motivation for Option
2, for me, is that I think all RDF URIs should work in browsers.  That
is, I should be able to take any RDF URI and paste it any reasonable
browser, and get some good HTML about the identified thing.

As far as I know, no one who is hosting an RDF vocabulary actually does
this yet, alas.

Now that I think about it, this should probably be added to the Recipes
for Publishing Vocabularies....  [1]

     -- Sandro

[1] http://www.w3.org/TR/swbp-vocab-pub/	
Received on Wednesday, 6 June 2007 19:29:30 UTC

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