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RDF & Trust & OWL & Layering (was Re: Meaning of URIRefs)

From: Sandro Hawke <sandro@w3.org>
Date: Mon, 28 Oct 2002 14:16:00 -0500
Message-Id: <200210281916.g9SJG0S06245@wadimousa.hawke.org>
To: pat hayes <phayes@ai.uwf.edu>
cc: www-rdf-interest@w3.org


> >  > Sure, strong-hint is fine, I guess. But look: suppose you in fact
> >>  just said something sensible about _:x, say that it was a cat and
> >>  also a Siamese, and suppose some other schmuk said that all Siamese
> >>  were dogs. I now have a contradiction derived from three sources.
> >>  There's nothing you can do to protect me from believing some nonsense
> >>  written by someone else. So no matter what *you* say, *I* need to be
> >>  always on my toes to make sure I don't just believe anything people
> >>  say using other people's urirefs. For that matter, I need to be on my
> >>  toes when reading what people say about their OWN urirefs; there is
> >>  lots of silly stuff out there which was written by its original
> >>  authors. There are even people who think that emailboxes are human
> >>  beings, for example.
> >>
> >>  >
> >>  >If some other web document (not at the animals URI) says that
> >>  >animals:Dog is a subclass of animals:Tree (disjoint from
> >>  >animals:Mammals), does the reader have any basis for thinking that
> >>  >_:spot is more legitimately an animals:Mammal than an animals:Tree?
> >>
> >>  Strict answer: no. Realistic answer: maybe, because owners of urirefs
> >>  are more likely to take some care with what they say using those
> >>  urirefs. Bottom line: you, the RDF reader, have to decide who you
> >>  trust. Caveat lector.
> >
> >I don't think it needs to be so bleak.
> 
> I don't see this prospect as in any way 'bleak'. Its the normal adult 
> human condition: you don't necessarily believe everything you hear.
> 

But it is not the normal condition for a computer program.  In
general, programs don't deal with trust -- their outputs are as
trustworthy as the least trustworthy of all their inputs (and their
code itself).

And of course the Semantic Web is intended largely for programs to
use.  It is not practical for a human-level judgement to be made about
the trustworthiness of every input, is it?  That's the bleakness I was
referring to -- the prospect of needing human judgement everywhere.

With the right architectural choices (which I'm advocating here), it
is not necessary.

> >I think people can handle
> >being dubious and weighing trust about a small number of sources,
> 
> I agree, but....
> 
> >and
> >if we have some kind of imports mechanism, that's all they'll need to
> >do.
> 
> ...they can do that without getting involved with 'imports' or 
> similar nonsense. All that anything that YOU can say cannot give me 
> any more confidence in anything else than I already have in you 
> (other than by through a kind of Googlish weighting scheme, in which 
> case your veracity is decided by your peers in any case. )
> 
> >
> >Imagine if the HTML web had two kinds of links: links to agreed-with
> >documents and links to not-necessarily-agreed-with documents.  People
> >wouldn't have to shift trust-gears when following the first kind of
> >link.
> 
> Yes, they would, because I might trust you as a tracker of current 
> news without trusting your actual opinions (I actually know people 
> like that, I swear), or vice versa (ditto).
> 
> >I suggest that this is largely the case; aside from
> >directory-style or search-result-style pages, links of the second type
> >are almost always clearly marked.   (Graphic style is also heavily
> >used; users re-engage their judgement when they come to a page that
> >looks very different.)
> >
> >Imagine users asking questions like "According to The Times, Is Dubya
> >President?".  The Times judges the trustworthiness of many sources, so
> >users don't have to.
> 
> Right, but that's a judgement about *the Times*, not about the Times' 
> opinions about who to trust.

I'm suggesting that for ease-of-use those should often be lumped together.

> >  (Of course users may chose to, if, for instance,
> >they don't really trust The Times.  But they shouldn't always have
> >to.)
> 
> Fine. Of course people will use reasoning like this. I don't see how 
> 'importing' helps with this, however.

If you don't want to lump thing together, it probably doesn't.

> >So RDF could really use a way to say another document is true.  It
> >might turn out to be owl:imports, or the URI-Ref mechanism I'm
> >proposing, or something else....
> 
> RDF is predicated on the (admittedly naive) assumption that all 
> documents are true. Saying so explicitly doesn't add anything to that 
> (unless you secretly don't believe that all documents ARE true, in 
> which case you probably shouldnt be using RDF, but should wait for a 
> more useful language like OWL to come into general use.)

I'm very surprised to hear you say that.   (especially since they're
written words :-)

1) I see no such predication in RDF.   I hear lots of people talk
about RDF applications which keep track of where data came from, so 
it can be properly weighed for trustworthyness.  You saw Mike Dean's
SONAT presentation, where he talked about using a form of reification
to track sources, and I can't begin to count the number of times I've
heard people talk about all this.  This applies to trusting machine
reasoning and accuracy of data, as well as the more-obvious issues of
identity and intent of information providers.

Of course RDF itself (not counting it's broken reification mechanism)
doesn't have any direct support for this stuff.  But it doesn't really
need to; source-tracking can be built around or on top of RDF in each
application. 

Are you just being precise about what's in the MT -- that the language
itself has no direct support for talking about trust issues -- or are
you really saying that people who want to track trust (like seemingly
every RDF user I know) should not be using RDF?

2) OWL is a different language from RDF only in the sense that English
using the word "Aardvark" is a different language from English which
does not use the word "Aardvark".  OWL offers precise definitions of
some few-dozen "words" which allow people to say things in RDF which
they could not say otherwise, unless they defined some of their own
words.

I meant to jump on this earlier, when you said that OWL and DAML were
"other KR languages [not RDF]".[1]  I can see why you might call them
different languages (natural language using technical jargon is kind
of another language), but that's also misleading.

...

The vision of RDF is that it's another solid step up the semantic
ladder, where bits and ascii/unicode are lower steps.  (Some people
put XML as a step here; I think it's just a step sideways.)  This step
puts us at the semantic Web.  At this step we have one single approach
to structuring (triples, binary relations), and one form of naming
(URI-Refs) [plus literals, but they're 90% carbohydrates].  Every
additional feature you might want to add, like the features of RDFS,
OWL, DAML+OIL, DC, CC, RSS, etc, is added by picking some identifiers
and fixing their meaning.

This thread has been about the fact that the approach of fixing their
meaning by making a W3C working group does scale.  This is just fine;
the URIs in the URI-Refs allow us to fix the meaning via documents on
the web.  That scales just fine.  Anyone with a website can define
their own vocabulary for ontology, rules, IPR licensing, syndication;
others can it those terms in their RDF, and it all scales and works.
Well, it does if we're clear about exactly how the website content
fixes the meanings of the terms -- which is what I'm trying to nail
down here.

      -- sandro


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Received on Monday, 28 October 2002 14:17:09 GMT

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