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Re: From syntactic to interpreted triple

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Wed, 10 Feb 2021 11:12:01 -0500
To: public-rdf-star@w3.org
Message-ID: <faea9373-9de9-5487-64a8-05a448f5f7e8@gmail.com>

On 2/10/21 10:54 AM, Olaf Hartig wrote:
> Hi Kingsley,
>
> On måndag 8 februari 2021 kl. 17:31:51 CET Kingsley Idehen wrote:
>> On 2/8/21 3:39 PM, Olaf Hartig wrote:
>>> REQUEST 1:
>>>     PREFIX owl: <http://www.w3.org/2002/07/owl#>
>>>     INSERT DATA { :fall owl:sameAs :autumn }
>>>
>>> Now you can do exactly the same steps as described in my email and, in the
>>>
>>> end, the endpoint will return true in response to the following query:
>>>     PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>>>     ASK WHERE { <<:autumn :hasWeather :rainy>> rdf:type :claim }
>> Hi Olaf,
>>
>> Do I accurately read the above as syntax-sugar (or shorthand) for the
>> following?
>>
>> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>> PREFIX : <#>
>>
>> ASK WHERE {
>>
>>                :thisClaim a rdf:Statement ;
>>
>>                           rdf:subject :autumn ;
>>                           rdf:predicate :hasWeather ;
>>                           rdf:object :rainy .
>>             }
> No, not in general. By the currently proposed semantics of RDF* [1,2], it is
> not generally the case that an embedded triple can be used as shorthand for
> the corresponding four reification triples. Consequently, something like this
> is also not possible in queries.


There are other proposed semantics.

>
> The reason for this is that, by the definition of the proposed semantics,
> embedded triples are referentially opaque (i.e., you can think of an embedded
> triple to be something similar to a literal). In contrast, an rdf:Statement
> (as described by the four reification triples) is referentially transparent;
> for instance, if you have the following reification triples (prefix
> declarations omitted)
>
>     :thisClaim rdf:type rdf:Statement .
>     :thisClaim rdf:subject :autumn .
>     :thisClaim rdf:predicate :hasWeather .
>     :thisClaim rdf:object :rainy .
>
> and you know that the URIs :autumn and :fall denote the same thing, then you
> can infer the following
>
>     :thisClaim rdf:type rdf:Statement .
>     :thisClaim rdf:subject :autumn .
>     :thisClaim rdf:subject :fall .
>     :thisClaim rdf:predicate :hasWeather .
>     :thisClaim rdf:object :rainy .
>
> which is something that you generally cannot do with embedded triples in RDF*.
>
> Having said that, in this thread here I have demonstrated that, even if we
> cannot draw such inferences for embedded triples in general, it is still
> possible to do so in specific contexts (namely, if an embedded triple is the
> subject or object of a particular type of nested triple).


I'm unclear as to what facility this refers to.

>
> Best,
> Olaf
>
> [1] https://github.com/w3c/rdf-star/pull/81
> [2] https://github.com/w3c/rdf-star/pull/88
>

peter
Received on Wednesday, 10 February 2021 16:12:16 UTC

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