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Re: CoIN: Composition of Identifier Names

From: Pierre-Antoine Champin <swlists-040405@champin.net>
Date: Tue, 13 Apr 2010 18:04:36 +0100
Message-ID: <4BC4A424.2010800@champin.net>
To: Robert Sanderson <azaroth42@gmail.com>
CC: Niklas Lindström <lindstream@gmail.com>, Linked Data community <public-lod@w3.org>
Here are my 2¢ about the opacity of resources.

First, let me point out that, contrary to what is often believed/claimed
(and I plead guilty of having done so), URI opacity is *not* a
constraint of the REST architectural style, at least as defined by
Fielding in his thesis [1].

Then, AFAIK, the main reference for URI opacity is [2]. The axiom states
that "you should not look at the contents of the URI string to gain
other information". If you read the following, you see that "you" mainly
means "your software". From this, I personaly draw two conclusions:

1/ URI opacity is a desirable feature of software handling URIs, not of
URIs themselves.

A hacker trying to get familiar with a source of URIs/linked data
should, on the other hand, be able to easily understand what is going
on... This is a good property, and does not contradict the opacity axiom
as long as that hacker does not make his/her software *relying* on such
an implicit understanding.

2/ Given a URI, a software should not try to reverse-engineer it.
However, the axiom does not prevent that a software be given a *rule* to
*produce* new URIs.

As a matter of fact, I would be surprised that TBL would discourage this
very mechanism which underlies all HTML-based forms (at least those
using the GET method). A form is nothing else than the specification of
a *whole set* of URIs, plus the technical tool to produce them easily in
your browser.


[1] http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
[2] http://www.w3.org/DesignIssues/Axioms.html#opaque

On 13/04/2010 17:11, Robert Sanderson wrote:
> A quick question...
> 2010/4/13 Niklas Lindström <lindstream@gmail.com>:
>> I've found it very valuable to formally declare the pieces from which
>> an URI is to be composed of. Especially in our environment where we
>> have a central design of the URI:s, but decentralized publishing of
>> data (which is of a somewhat rich and varied nature).
> How does this mesh with URIs being opaque?  If the URIs were actually
> opaque and treated as such, then formally declaring the parts would be
> a non-issue.  It seems that this ideal is being increasingly watered
> down or ignored... is that intentional, and is it a good or bad thing?
> Thoughts?
> Rob Sanderson
Received on Tuesday, 13 April 2010 17:05:09 UTC

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