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RE: HTTP inference rules [was: AWWSW minutes from today]

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Mon, 11 Feb 2008 10:11:11 +0000
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>
CC: "public-awwsw@w3.org" <public-awwsw@w3.org>
Message-ID: <9674EA156DA93A4F855379AABDA4A5C611950F7358@G5W0277.americas.hpqcorp.net>

Hello David,


> -----Original Message-----
> From: Booth, David (HP Software - Boston)
> Sent: 10 February 2008 09:00
> To: Williams, Stuart (HP Labs, Bristol)
> Cc: public-awwsw@w3.org
> Subject: HTTP inference rules [was: AWWSW minutes from today]
>
> > From: Williams, Stuart (HP Labs, Bristol) [ . . . ]
> > > From: David Booth
> > [ . . . ]
> > > Thanks for your comments on
> > >>> http://esw.w3.org/topic/AwwswDboothsRules
> > [ . . . ]
> > > Yes, I was trying to say that the app knows to use the
> > > follow-your-nose principle, but I guess I should have worded it
> > > better.  I've hopefully improved the wording now.  Check the wiki
> > > again and see what you think:
> > > http://esw.w3.org/topic/AwwswDboothsRules
> > >
> > The page still speaks of assumptions... I was trying to say that what
> > you are speaking of is not an assumption, I believe that its is more
> > axiomatic in the architecture of the web.
>
> Which assumptions do you mean?  Can you be specific?

# And we'll assume that the app knows to "follow its nose" to
# learn more about <...#dan> by dereferencing the racine
# of its associated URI...

Ok... I guess it depends on where the weight of assume falls... I was reading it as a stated assumption that to (roughly) dereference(access) <racine#fragment> that you have to (try-to) deference(access) <racine>...

I can see other ways of reading this: ie. the assumption is not about the mechanics of dereference(access), but about the app knowing or having a strategy for, given a URI, how to retrieve either a representation or a description (with little control over which at the outset - as things stand).

Anyway I suspect that we'd done that one to death.

<snip/>

> > [ . . . ]
> > >> # And we'll assume that in parsing the above triple, the app
> > >> *also* automatically asserted the following triple:
> > >> # <http://dbooth.org/2008/httpinf/moon.rdf#themoon> log:uri #
> > >> "http://dbooth.org/2008/httpinf/moon.rdf#themoon"^^xsd:anyURI .
> > >>
> > >> This is an obvious tautology... and as such harmless...
> > >>
> > >
> > > I don't think it is a tautology.  AFAICT this is a
> > > necessary assumption, since in the RDF semantics,
> > > <http://dbooth.org/2008/httpinf/moon.rdf#themoon> denotes a
> > > resource.
> > The URI is at the syntactic level, not semantic.
> > How would any rules otherwise know what URI had been used to denote
> > that resource?
> > >
> > "The thing denoted by the URI 'xxx'  is denoted by the URI 'xxx'."
> >
> > Looks like a straight tautalogy to me.
>
> It sounds like you are confusing syntactic and semantic
> domains.

I don't think so.

> Semantically
> <http://dbooth.org/2008/httpinf/moon.rdf#themoon> denotes a
> particular resource, and nothing more.  That exact same
> resource could just as well be denoted by some other URI,
> such as http://example/fribjam , in which case the above
> could have been written as:
>
>   <http://example/fribjam> log:uri
>       "http://dbooth.org/2008/httpinf/moon.rdf#themoon"^^xsd:anyURI .
>
> which no longer looks like a tautology even though it would
> have the *exact* same semantics.

Ok... yes, that's not a tautology, but it is different from the original statement. It's probably closer to the blank node form which i mentioned in an earlier response.

        [] log:uri  "http://dbooth.org/2008/httpinf/moon.rdf#themoon"^^xsd:anyURI .

Anyway, we've probably killed this one enough as well.

> > [ . . . ]
> > >> 2) I think this will quickly get messy with some means to
> > >> distinguish inferences derived from different responses.
> > >> Over time
> > >> the multipicity of different responses and monotonic assertions
> > >> inferred from them may lead to inconsistent KBs.
> > >>
> > >
> > > Correct.  It does not prevent a URI owner from issuing conflicting
> > > URI declarations at different points in time, thus causing a "URI
> > > collision":
> > > http://www.w3.org/TR/webarch/#URI-collision
> > > The architecture does not prevent URI collisions, but
> > > admonishes URI owners and users to avoid them.   If an owner
> > > issues conflicting URI declarations, users are likely to avoid using
> > > the URI.
> > >
> > I'm not talking about URI-collision - I taking about a KB which has
> > become inconsistent... where it is possible to prove that there are no
> > intepretations which satsify the model.
> > [ . . . . ]
>
> Aren't you talking about different URI declarations being
> served at different times, thus causing inconsistencies over
> time?

I'm not so much focussed on URI declarations as a general observation that accumulating knowledge over time, without isolating temporal context, may, over time, lead to a KB that becomes inconsistent and unusable.

        :theTrafficLight :isAt :green .
        :theTrafficLight :isAt :red .


>  If so, then the URI is being declared differently at
> different times, i.e., the same URI is used to denote
> different things at different times, which is one form of URI
> collision.  (I.e., the same party is using the URI to denote
> different things at different times, rather than different
> parties using the URI to denote different things.)  If that
> isn't what you are talking about then please explain.

I don't quite know how to square that with an earlier response which seemed to take a relaxed stance about can be 'in' a URI declaration.

<quote>
> >
> > Major problems:
> >
> > 1) I don't see that the conclusion necessarily follows from the
> > premises. It *only* follows of ?formula says something 'declarative'
> > (your word) about (the referent of) ?u.
> > Otherwise it could be saying things about a whole bunch of things and
> > may say nothing at all about (the referent of) ?u.
>
> Correct.  That would be a poor quality URI declaration, and users may thus choose to avoid using that URI, but being poor quality does not prevent it from nonetheless being a URI declaration.
</quote>


> David Booth, Ph.D.
> HP Software
> +1 617 629 8881 office  |  dbooth@hp.com
> http://www.hp.com/go/software
>
> Opinions expressed herein are those of the author and do not
> represent the official views of HP unless explicitly stated otherwise.
>

Stuart
--
Hewlett-Packard Limited registered Office: Cain Road, Bracknell, Berks RG12 1HN
Registered No: 690597 England
Received on Monday, 11 February 2008 10:13:55 GMT

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