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Re: Can RDF say anything about anything?

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 12 Feb 2003 09:40:28 +0000
Message-Id: <>
To: Frank Manola <fmanola@mitre.org>
Cc: pat hayes <phayes@ai.uwf.edu>, RDF core WG <w3c-rdfcore-wg@w3.org>

[Switching thread to RDF-core]

At 07:42 PM 2/11/03 -0500, Frank Manola wrote:

>pat hayes wrote:
>>>I know this thread has died down, but I'd like to get some clarification
>>>on exactly what needs fixing in the Primer.  The Primer doesn't say (I
>>>don't know how to interpret "indicate") "that RDF can be used to let
>>>anyone 'say anything they want about existing resources' ".  What the
>>>Primer says, following some examples, is "These examples also illustrate
>>>one of the basic architectural principles of the Web, which is that
>>>anyone should be able say anything they want about existing resources
>>>[BERNERS-LEE98]."  That seems like a reasonable statement under the
>>>circumstances (part of the circumstances being that the Primer is
>>>clearly not describing a rule that is to be applied by an RDF/XML
>>>parser).  Are there problems with the actual statement in the Primer?
>>I think the problem might be with any form of words like "able say 
>>anything they want". In one way of understanding these words, they mean 
>>something like, "not prohibited from saying anything they feel like 
>>saying using the formalism, on any topic they choose", which of course is 
>>so harmless as an observation that it hardly seems worth saying. But in 
>>another way of understanding those words is "enabled by the formalism to 
>>have the ability to express any proposition" which is an absurd claim. I 
>>think the words were meant in something close to the first sense, but are 
>>being read in something close to the second sense.

Yes, but there's something in the *goals* of RDF that aims to be universal, 
but that goal is not completely achieved, or even possible, 
technically.  "say anything about anything" is an aspirational statement.

>I think the main problem is that a comment in the Primer about an 
>*example* is being used to derive a comment *not* in the Primer about the 
>power of *the formalism used in the example* (RDF/XML), and then issues 
>are being raised about the *derived* comment.  I suppose such a derivation 
>can be made, but I can't see very many readers of the Primer actually 
>making it, and they would be wrong if they did.  I certainly can't imagine 
>very many readers of the Primer reading that statement, and then 
>complaining that they were unable to use rdf:ID as a predicate (for example).
>Issues directed at the actual text in the Primer would be things like:
>1. Anyone being able to say anything they want about existing resources 
>isn't a basic architectural principle of the Web.  If that's an issue, I 
>refer you to [BERNERS-LEE98], which says "The Web works though anyone 
>being (technically) allowed to say anything about anything."  I suppose it 
>could be argued that the Primer doesn't characterize that properly, or use 
>the exact quotation, but the quotation seems to go even further than the 
>Primer does, if you interpret it as applying to what RDF allows, rather 
>than what the Web is trying to do, since it doesn't restrict itself to 
>saying things about "resources".

I like that Berners-Lee quote, because I think it is unarguable when 
applied to ordinary web pages.

Here's an attempt to build upon that:
The Web works through anyone being (technically) allowed to say anything 
about anything.  RDF is a limited formalism, but follows this ideal by 
allowing expression of arbitrary propositions about any subject matter, 
within the limitations of its formalism.

I think it behoves Concepts to be a bit more precise about the extent of 
that formalism;  Pat used some words recently (something like "binary 
propositional subset of EC logic") that I'd like to steal.


>2.  The examples provided don't illustrate that principle of the Web.  I 
>think that they do, even though they don't do so exhaustively.
>>>"Peter F. Patel-Schneider" wrote:
>>>>  From: Brian McBride <bwm@hplb.hpl.hp.com>
>>>>  Subject: Re: Can RDF say anything about anything?
>>>>  Date: Fri, 31 Jan 2003 06:51:29 +0000
>>>>  > At 09:48 30/01/2003 -0500, Peter F. Patel-Schneider wrote:
>>>>  >
>>>>  > >Can RDF say anything about anything?
>>>>  > >
>>>>  > >The RDF documents are contradictory on this point.  The Primer 
>>>> indicates
>>>>  > >that RDF can be used to let anyone ``say anything they want about 
>>>> existing
>>>>  > >resources'' with no exception for the resources used by RDF.
>>>>  > > 3.2] Concepts says
>>>>  > >that ``RDF is an open-world framework that allows anyone to make 
>>>> simple
>>>>  > >assertions about anything''.  [Section 2.2.6, and elsewhere]
>>>>  > > However, Concepts also says that ``Certain
>>>>  > >URIs are reserved for use by RDF, and may not be used for any 
>>>> purpose not
>>>>  > >sanctioned the RDF specifications.'' [Section 3.7]
>>>>  > >
>>>>  > >What is the situation here?
>>>>  >
>>>>  > Peter,
>>>>  >
>>>>  > As this comment affects several documents, I'll respond.
>>>>  >
>>>>  > As a general point, it is helpful if you can provide links to the 
>>>> sections
>>>>  > of documents where you have a problem with the text, or at the least
>>>>  > section numbers.
>>>>  Isn't that what the Search/Find capabilities of browsers are for?  I 
>>>> would
>>>>  expect that an interested reader would want to know where else Concepts
>>>>  talks about being able to say anything about anything.  I've added 
>>>> section
>>>>  numbers to my comment above.
>Frank Manola                   The MITRE Corporation
>202 Burlington Road, MS A345   Bedford, MA 01730-1420
>mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875

Graham Klyne
Received on Wednesday, 12 February 2003 05:05:37 UTC

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