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Re: httpRange-14: some dimensions of space of positions

From: Dan Connolly <connolly@w3.org>
Date: Tue, 03 May 2005 08:30:30 -0500
To: "Roy T.Fielding" <fielding@gbiv.com>
Cc: Harry Halpin <hhalpin@ibiblio.org>, www-tag <www-tag@w3.org>
Message-Id: <1115127030.28180.83.camel@localhost>

On Tue, 2005-05-03 at 00:47 -0700, Roy T.Fielding wrote:
> On Apr 29, 2005, at 8:34 AM, Dan Connolly wrote:
> > What I'm suggesting is that you can coin terms for
> > the class "person" (or "agent") and the class "document",
> > say that they're disjoint, and say that something
> > is in one of them (and hence not the other), hence
> > disambiguating between a person an their homepage.
> >
> > I can write this to say that I mean for
> > http://www.example.org/PatHayes to denote his homepage:
> >
> >   foaf:homepage a owl:InverseFunctionalProperty;
> >     rdfs:domain foaf:Agent;
> >     foaf:range foaf:Document.
> >   foaf:Agent owl:disjointFrom foaf:Document.
> >
> >   _:somebody foaf:homepage <http://www.example.org/PatHayes>.
> >
> >
> > And if somebody else writes
> >
> >   adams:HoopyFrood rdfs:subClassOf foaf:Agent.
> >   <http://www.example.org/PatHayes> a adams:HoopyFrood.
> >
> > then the machine can compute that we disagree.
> Yes, and one might even think the disagreement is obvious,
> right up to the point where you realize that documents
> are also agents, and while they may not have friends they do
> occasionally have home pages, and it is the statement that the
> two are disjoint that may be in error.

Error? The statement that the two are disjoint may be
the source of the disagreement, but it seems odd to
say that it's an error; more like an opinion with which
some people disagree.

> For example, let's consider Tim Bray's blog "ongoing".  Would you
> claim that is a document or an agent?

for the purpose of this example, I'd say it's a foaf:Document.

Looking up the documentation, it seems that the foaf
project has not yet decided that
  foaf:Agent owl:disjointFrom foaf:Document.

so it's perhaps not as good an example as
cyc:Agent vs cyc:Artifact.

"#$Agent   agents

The collection of #$Agent-Generics (q.v.) that are not tangible
artifacts (cf. #$AgentiveArtifact)."

>   Is it alive?  Does it have
> a life span?  Does it have a physical effect on other agents?
> Does the fact that ongoing consists of a set of authored entries
> that change over time mean it is more like a document or less
> like a document?
> Does "ongoing" have a homepage, or does it just have a URI?

I presumed you were speaking relatively formally
and you meant the thing with URI
http://www.tbray.org/ongoing/ when you originally
said "ongoing".

> I won't claim that I have the answer for any of those questions.
> httpRange-14 is a statement that those questions have been answered
> in a meaningful way by the scheme used to identify the blog.
> Regardless, people use URIs to identify resources and don't care
> whether or not a computer thinks two poorly-defined sets are
> disjoint.  There is no way that a system can determine whether a
> user has supplied a URI for the purpose of direct, ontologically
> unambiguous identification of a resource, or of simple indirect
> identification via whatever URI seems most useful at the time.

There's no way for a system to tell whether a user has made
a mistake in encoding their knowledge, but there are formats
that are explicit about direct vs indirect identification.

> That is a problem of reference that will not be solved by changing
> the syntax of the identifiers.
> ....Roy
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Tuesday, 3 May 2005 13:31:21 UTC

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