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

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sat, 1 Oct 2011 12:43:31 +0100
Cc: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-Id: <52B4E978-4C22-4130-9FE9-302094990FE7@cyganiak.de>
To: Sandro Hawke <sandro@w3.org>
On 30 Sep 2011, at 20:11, Sandro Hawke wrote:
>> Named graphs are key to trust and
>> provenance. Trust and provenance must happen at a lower level in the
>> stack, before reasoning and inference kick in. W3C's version of the
>> layer cake, where trust sits above reasoning, cannot work. The moment
>> you reason with OWL over untrusted data, you [have problems].
> 
> I don't think we need to throw out reasoning on the fourth column.  As
> long as we're careful about what it means -- eg: it denotes an IR which
> may give you a Graph -- I think people are free to layer inference and
> trust/provenance reasoning in various ways.  
> 
> Let's say you are using three Web data sources, S1, S2, and S3.  S1 and
> S2 give just triples.  S3 is an ontology (perhaps a RIF document); we
> don't really care if it's triples.   What's the problem with merging the
> triples, doing the inference, and using the result, knowing it is no
> more trustworthy than the least of S1, S2, and S3?  

Well, the way I see it, what happened here is that the system (on behalf of some user, I presume) decided that S1, S2 and S3 are good enough – sufficiently trustworthy – for the task at hand.

Provenance information is the basis for trust decisions. The system made the trust decision before it merged the graphs.

> Specifically, the
> provenance of your output involves the provenance of S1, S2, S3, and the
> reasoning steps you took. In detailing those reasoning steps, I think the identifiers for S1, S2, and S3 will be useful.

Sure. What I said was that you can't do OWL reasoning over untrusted data sources. I didn't say that you can't use graph names when recording processing steps that were taken.

> But for a later-stage provenance system to reason about S1, S2, and S3
> is fine, I think.

I don't know what it means when you say “a provenance system reasons about XYZ”. I suppose you're not talking about OWL reasoning.

(Sandro, you use the word “reasoning” a lot and I never know what you mean. Can you point me to a W3C definition, or provide your own?)

Best,
Richard
Received on Saturday, 1 October 2011 11:44:02 GMT

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