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Re: XML Schema draft populates the intersection of Language and InformationResource [ISSUE-14 httpRange-14]

From: Richard Cyganiak <richard@cyganiak.de>
Date: Mon, 1 Oct 2007 23:41:10 +0200
Message-Id: <A3548EFF-AA1C-4785-8C75-B9E4D31F098D@cyganiak.de>
Cc: www-tag@w3.org
To: "Chimezie Ogbuji" <chimezie@gmail.com>

Chimezie,

On 30 Sep 2007, at 15:02, Chimezie Ogbuji wrote:
[snip]
> If you consider URI identification as equivalent to an 'inert' form
> [1] of denotation then that would suggest that webarch (with respect
> to 'meaning') considers assertions made about (and within)
> webarch:def-information-resource instances as the *only* commitments
> relevant to an intelligent agent.  By "within" - I mean the process of
> dereferencing a racine and the follow-your-nose-to-an-appropriate-RFC
> mechanism you outlined before.

I don't understand. Webarch is not concerned with knowledge  
representation at all. It describes a transfer and identification  
layer. RDF and OWL are KRs built on top of that layer. Webarch is not  
concerned with “intelligent agents”. It is concerned with resources  
and their representations.

Even if Webarch *was* a KR, I have no clue where you get the idea  
that only assertions about information resources should be relevant.  
It doesn't seem to follow logically from anything you or I said.

I do not know what you mean by “inert denotation”. Perhaps you are  
trying to contrast the term “identify”, in the webarch sense (such as  
in Uniform Resource Identifier) with the term “denote”, in the model  
theory sense? There were interesting posts from Pat on this  
distinction, elsewhere in this thread, that helped me understand the  
difference between those notions.

> "The third role for a representation is as a fragmentary theory of
> intelligent reasoning. This role comes about because the initial
> conception of a representation is typically motivated by some insight
> indicating how people reason intelligently, or by some belief about
> what it means to reason intelligently at all." -- Role III: A KR is a
> Fragmentary Theory Of Intelligent Reasoning
>
> Given the inert nature of URI 'denotation', it is clear that web
> architecture (even when equipped with the very binary inference
> mechanism afforded by httpRange-14) does not satisfy this role by
> itself.

Neither is it meant to. The Web is not a KR. Though it can act as a  
transfer and distribution mechanism (and subject matter) for one.

> "Finally, knowledge representations are also the means by which we
> express things about the world, the medium of expression and
> communication in which we tell the machine (and perhaps one another)
> about the world. This role for representations is inevitable so long
> as we need to tell the machine (or other people) about the world, and
> so long as we do so by creating and communicating representations." --
> Role V: A KR is a Medium of Human Expression
>
> NOTE: I believe the use of the word representation here is completely
> orthogonal to web-arch's use of the same word.

Yes.

> If indeed a KR is meant to work as a medium for expression on our
> behalf it would have failed with respect to those expressions that are
> about things that do not emit codes over a transport protocol.  Before
> there were transport protocols, there were expressive languages
> (including the one I'm currently communicating to you with), so it
> follows that the 'universe of discourse' of web-architecture is a
> (very small) subset of those 'things' for which it is useful to
> formulate expressions and thus it is not a very useful medium of human
> (or machine - for that matter) expression.

The “universe of discourse” (if you insist on using that term) of web  
architecture is the set of all things that can be identified by a URI  
--- thus, everything. It is *not* limited to things that do emit  
codes over a transport protocol, though it has a great deal more to  
say about those resources than about others. Which is exactly why  
there is a desire to layer powerful KRs on top of it, so we can say  
more about those other things.

> This paper is easily my favorite reference on KR as it describes it as
> something of an architectural style rather than in terms of a specific
> KR (which often loses something in the translation).  In addition, my
> running definition of "intelligent agent" is any bit of software that
> seeks to take advantage of the roles described in that paper on behalf
> of a human.
>
>> Hm. I find it curious that you choose to ignore those parts of the
>> relevant specifications that actually address some of the mismatch
>> you posit.
>
> Fair enough.  Richard (or any one else for that matter),  Could you
> point me to those parts I ignored that address some of the disconnects
> I've mentioned above (explcitely)?

Section 7 of rdf-concepts seems to be relevant. Or maybe not, I still  
don't quite understand where you're coming from.

>> Then Pat is simply asserting that <PatHayes.html> is a member of two
>> disjoint classes. OWL and RDF allow us to do such things.
>
> Syntactically, yes we can do such things.  But I was more concerned
> about consistency (which is critical for intelligent agents).  In this
> case we would have inconsistency between what a (first-class) KR
> asserted and the (very weak) assertions about the nature of a referent
> which follows from httpRange-14

Your assignment of relative strengths to these two assertions is  
entirely arbitrary. I could argue that a TAG decision with its likely  
consequences for future W3C and IETF standards is much stronger than  
a statement by some guy about some web page. After all, you can't  
redefine owl:Class as something else, so why would you expect to be  
able to redefine an information resource as something else?

> (if you consider it an ontological
> commitment - I certainly don't).

Perhaps this might be the problem? If you're not ontologically  
committed to the existence of the Web (i.e. that http://www.w3.org/  
denotes a web page in any possible interpretation), then it's not  
surprising that you run into all sorts of problems.

>> To spell it out: httpRange-14 says, if it emits representations, then
>> its a webarch:informationResource. From AWWW we can conclude that
>> webarch:informationResource owl:disjointWith foaf:Person. Thus, if it
>> emits representations and claims to be a person, there's a
>> contradiction.
>> What is your claim? That this is incompatible with rdf-mt?
>
> My claim is that this would be (blatantly) incompatible with the
> rdf-mt/OWL-guided interpretation that would follow from the assertions
> in the document.

It goes beyond rdf-mt, thus it is a semantic extension. That does not  
mean it is blatantly incompatible.

> My secondary claim is that this incompatibility is a
> strong indicator that web-arch is impersonating a KR at best and the
> consequences are dire for future agents.

Interesting. I still haven't seen much backup for these  
pronouncements of impending doom.

>> As I said before, I *do* believe that RDF's use of URIs should be
>> subject to the RFCs governing URI-space. But note that the RFCs place
>> no restriction whatsoever on the denotation of large chunks of URI
>> space.
>
> Yes, but then we have the following AWWW assertion:
>
> A URI owner SHOULD provide representations of the resource it  
> identifies
>
> Sounds like a restriction on URI denotation to me (at least with
> respect to the use of URIs on the hypertext web)

I do not see how this recommendation does in any way restrict URI  
denotation.

>> The most interesting edge cases are http:// URIs that answer 303, and
>> URIs with fragment identifier where the racine answers an  
>> application/
>> rdf+xml representation. They can denote whatever you want, but you
>> should set up an associated description that tells the rest of the
>> world what you intend to denote. As you know, this has certain
>> benefits and certain costs, but those are a separate topic.
>
> What makes these any more 'interesting' than URIs which do not have
> representations but which denote referents (in the real world) which
> are crucially important to certain domains?

I *was* talking about URIs which do not have representations but  
which denote referents in the real world.

> The only 'interesting'
> characteristic is that they 'fit' into the web-arch style, but this
> should be icing on the cake not a necessary component.

I don't understand what you mean by this.

Anyway, I'm a little frustrated by this thread. We don't seem to get  
any closer to understanding, and my attempts at clarification do not  
seem to be effective. Perhaps time to let it die down -- I simply do  
not see the problem that bothers you.

Richard



>
> -- Chimezie
>
Received on Monday, 1 October 2007 21:41:31 UTC

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