W3C home > Mailing lists > Public > www-rdf-interest@w3.org > April 2002

Why Hash?

From: Sandro Hawke <sandro@w3.org>
Date: Sun, 07 Apr 2002 13:19:08 -0400
Message-Id: <200204071719.g37HJ8508029@wadimousa.hawke.org>
To: Uche Ogbuji <uche.ogbuji@fourthought.com>
Cc: www-rdf-interest@w3.org

> My only comment is that I do hope we can find our way to banishing the odd use 
> of URI fragments in RDF except as needed to denote in-line resources attached
> to a particular serialization document.
> I, for one, do not use URI fragments in my vocabularies, and at Fourthought, 
> we consider it "best practice" not to do so.
> Let's keep serialization issues out of the idea of universal identification, 
> where possible.

Interesting.  I've been thinking I need to write a "Why Hash? (Why Use
URI-References as RDF Identifiers)" paper.  I'll try out the argument

I think any string which wont be accidentally reused makes a decent
universal identifier.  UUIDs/GUIDs/tags, are fine for this.

Unfortunately, they don't help us locate any information about the
things identified.  It would be very nice to use RDF identifiers kind
of like web address: you see one on the side of a bus, you type it in,
and you get some interesting information.  For this to work with
UUIDs, we'd need something like google in the background.  Seems like
a bad idea.

The URI-Reference approach (which I've adopted, after flirting with
tag URIs) is to use URI-References as object identifiers, and URIs as
knowledge-base identifiers.  Doing a GET on the URI contained in a
URI-Reference gives you the owner's information about the thing
denoted by the URI-Reference.  The acceptable content types in the GET
will guide the server to providing the information in text/html,
application/rdf+xml, or other formal or informal knowledge
representation languages.  You may have many other sources of
information, of course, and the owner may not provide any information,
but you at least have one place to start.

A nearby approach, which I don't like, is to use URIs to denote
everything.  With this plan, the owner has the same ability to publish
easily-found information, but the whole system seems more confusing.
Now we're back to wondering what exactly http://www.w3.org/ denotes.
With the previous plan it's clear: it denote a collection of
information (published by the W3C, probably about the W3C and other
things).  If you use URIs for everything, you're essentially running a
great risk of accidental identifier re-use.

    -- sandro
Received on Sunday, 7 April 2002 13:21:01 UTC

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