W3C home > Mailing lists > Public > public-lod@w3.org > June 2011

Re: Squaring the HTTP-range-14 circle [was Re: Schema.org in RDF ...]

From: David Booth <david@dbooth.org>
Date: Thu, 16 Jun 2011 20:46:17 -0400
To: Linked Data community <public-lod@w3.org>
Cc: Pat Hayes <phayes@ihmc.us>, Danny Ayers <danny.ayers@gmail.com>, Jason Borro <jason@openguid.net>, Tim Berners-Lee <timbl@w3.org>
Message-ID: <1308271577.2165.51285.camel@dbooth-laptop>
On Thu, 2011-06-16 at 16:38 -0500, Pat Hayes wrote:
> On Jun 15, 2011, at 8:27 PM, Danny Ayers wrote:
[ . . . ]
> > There's nothing around HTTP that says it can't be
> > given the same name, and it's a darn sight more useful than a
> > wave-over-there redirect or a random fish/bike association. I can't
> > see anything it breaks either.
> 
> OF COURSE it breaks things. It might be true to say that Sasha is a
> Collie-German Shepherd cross, but Sasha's description or web page
> certainly isn't. It might be true to say that the description is
> written in RDF, but Sasha isn't. 

Let's go further and clarify exactly what breaks: Using the same URI
both for Sasha and Sasha's web page breaks *some* applications and not
others.  Applications that need to distinguish between dogs and web
pages will find the URI ambiguous; applications that do not will be
perfectly happy.  This state of affairs is a universal fact of life that
is true of *all* possible distinctions that may be made, regardless of
whether the distinction is between web pages and dogs, or between
different kinds of dogs, or between different kinds of proteins or
anything else. 

Except in the absurdly reductionist sense that *every* URI is ambiguous
(because finer distinctions can always be made), whether a URI is
ambiguous or unambiguous is *not* a fundamental property of the URI:
ambiguity is relative to the *application* that is using that URI. 

Given this fact of life, I maintain that permitting the same URI to
denote both a web page and a dog does *not* break the architecture of
the web.  

I agree with TimBL that this is a design choice about the architecture
of the web, and a clean, extensible architecture is needed.

I agree with TimBL that 303 (and hash URIs) are useful for those who
*choose* to distinguish between the web page and something else.

I agree with TimBL that the httpRange-14 rule is very useful, even if it
was not ideally stated, and should *not* be abandoned.  However, the
major flaw lies not in the httpRange-14 rule itself, but in the
associated assumption that a URI cannot sensibly denote both an
"information resource" and a dog:
http://www.w3.org/TR/webarch/#def-information-resource
This assumption is fatally flawed because: (a) it attempts to make an
IR/non-IR distinction that can never be nailed down precisely (as
several people have pointed out); and (b) it unnecessarily elevates one
particular axis of ambiguity over all others.  It is analogous to a rule
that says "all URIs for dogs MUST distinguish between male dogs and
female dogs": the only applications that break without this rule are the
ones that *need* to distinguish between male dogs and female dogs.  All
other applications will continue to work just fine without it.   And
that is exactly the way it should be for *any* axis of ambiguity.

I agree with TimBL that it is *good* to distinguish between web pages
and dogs -- and we should encourage folks to do so -- because doing so
*does* help applications that need this distinction.  But the failure to
make this distinction does *not* break the web architecture any more
than a failure to distinguish between male dogs and female dogs.


-- 
David Booth, Ph.D.
http://dbooth.org/

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Friday, 17 June 2011 00:46:44 UTC

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