W3C home > Mailing lists > Public > public-rdf-wg@w3.org > June 2012

Re: dataset semantics being connected to the state of the web

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 8 Jun 2012 08:42:54 -0500
Cc: Sandro Hawke <sandro@w3.org>, Richard Cyganiak <richard@cyganiak.de>, public-rdf-wg@w3.org
Message-Id: <D779876E-BD25-49CC-8CEB-DF2F4F7589A1@ihmc.us>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>

On Jun 8, 2012, at 7:57 AM, Peter F. Patel-Schneider wrote:

> If the only interpretations are those that support <i,G> if dereferencing I produces G, then, yes, <i,G> will be a consequence of anything (and nothing).


>  Of course, this would mean that entailment changes whenever the web changes.

Not really. Entailemnt is DEFINED as preservation of truth. It is truth that changes when the Web changes, not entailment. This happens in natural language discourse. The truth of "it is raining" changes according to the time and place it is uttered. When it is true, its truth does not depend upon any presumptions, so it acts logically as a tautology, so is entailed by anything, speaking technically. Of course we don't usually describe it that way, as we recognize it as an observation about the local state of affairs. Similarly, what dereferences to what is an observation about hte current state of the Web.

> I do not believe that this is a desirable feature to put in RDF.

I disagree. Or at least, I would want to have reasons for objecting to it, given its obvious utility. I wish there were some way to record this with a time/place stamp, however. 


> peter
> On 06/08/2012 08:28 AM, Sandro Hawke wrote:
>> On Fri, 2012-06-08 at 10:51 +0200, Richard Cyganiak wrote:
>>> Hi Sandro,
>>>>> I've heard you say two mutually incompatible things:
>>>>> 1. A Turtle file published at<i>  containing graph G is an RDF dataset with only named graph<i,G>
>>>>> 2. A Turtle file published at<i>  containing graph G is an RDF dataset with only a default graph
>>>>> Which one is it? It can't be both.
>>>> If I said (1), it was a mistake.
>>>> I would rephrase (1) as a conditional:
>>>>   A.  If it is true that a turtle file serializing G is what is
>>>> published at<i>,
>>>>   B.  Then the dataset consisting of the named graph<i,G>  is true.
>>> -1.
>>> We can postulate the existence of a *specific* dataset, let's call it
>>> the “web dataset”, and can say that under the condition above the
>>> g-pair<i,G>  is true in the web dataset.
>> Yes.     I'm not sure that's the most useful framing, but it's quite
>> reasonable.
>>> (Formally, this could be done
>>> as a semantic extension, let's call it W-entailment (for web). So if A
>>> is true then *every* dataset W-entails the g-pair<i,G>.)
>> The logicians can correct me, but that seems to me like a non-standard
>> way to use entailment.  Whether one statement entails another is
>> something that can be determined purely by looking at the two statements
>> and understanding the logic of the language they are written in.
>> Entailment isn't about what statements happen to be true of the domain
>> of discourse.

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Received on Friday, 8 June 2012 13:43:33 UTC

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