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Re: why I don't like named graph IRIs in the DATASET proposal

From: Eric Prud'hommeaux <eric@w3.org>
Date: Sun, 2 Oct 2011 09:15:26 -0400
To: Richard Cyganiak <richard@cyganiak.de>
Cc: Sandro Hawke <sandro@w3.org>, Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-ID: <20111002131525.GF20425@w3.org>
* Richard Cyganiak <richard@cyganiak.de> [2011-10-02 13:18+0100]
> On 2 Oct 2011, at 00:29, Eric Prud'hommeaux wrote:
> > As to doing inference over "untrusted data", (A) I think that *all* trust is predicated,
> 
> The definition I work with is something like this:
> 
> “trusted data” = “data assumed by someone to be of sufficient quality for some purpose”
> 
> > and (B), it really doesn't matter if Bob claims to be a <Genius> or he claims to be a <Super-genius> and inferencing leads me to discover that he believes himself a <Genius>, my trust of the inferential closure is pretty much identical to my trust of his homepage.
> 
> It matters if Bob claims that all vegetarians are geniuses.
> 
> You'll have to carefully filter Bob's graph in order to remove anything of that sort before you can pass it to your inference engine. That's my point: you have to make trust decisions *before* you can do OWL reasoning.

Given:
  I believe Bob to be an authority about whether he's a vegitarian.
  I don't believe Bob to be an authority about whether he's a genius.
  Bob (being a genius) can come up with many tricky ways to imply that he's a vegetarian or a genius.

I can sanitize Bobs homepage before inferencing to remove things like:
  <Bob> a <Genius> .
  <Bob> a <Foo> . <Foo> rdfs:subClassOf <Genius> .
  <Bob> <bar> <Foo> . <bar> rdfs:subPropertyOf rdf:type . <Foo> rdfs:subClassOf <Genius> .
  <Genius> owl:equivalentClass  [ a owl:Restriction ; owl:onProperty rdf:type ; owl:hasValue <Vegetarian> ] .
  ...
The simplest tool to use is a reasoner which generates complete evidence for every inference. I can then carefully attempt to remove the parts of Bob's homepage graph which led me to conclusions about <Genius>s without disturbing the ones that led me to conclusions about <Vegetarian>s. Given that this is a *hard* problem, I think my confidence goes sharply up if I let full inference happen on Bob's homepage but treat the inferential closure with the same predicated trust that I would his raw homepage.


> > I believe the only exception to this is when you don't entirely trust the ontology 'cause it's got some ragged edges (as happens with large OWL-ified medical ontologies like SNOMED-CT).
> 
> You're making an assumption of strong A-Box and T-Box split, where the T-Box is hand-selected and trusted. That's my point: you have to make trust decisions *before* you can do OWL reasoning.
> 
> Best,
> Richard

-- 
-ericP
Received on Sunday, 2 October 2011 13:16:05 GMT

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