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Re: RDF* semantics

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Wed, 14 Aug 2019 11:01:19 -0400
To: Olaf Hartig <olaf.hartig@liu.se>, "public-rdf-star@w3.org" <public-rdf-star@w3.org>
Message-ID: <34ed9bc6-3a9f-3d51-ce16-5de2bb2d9dd7@openlinksw.com>
On 8/8/19 6:13 AM, Olaf Hartig wrote:
> On Wed, 2019-08-07 at 12:04 -0400, Kingsley Idehen wrote:
>> [...]
>>>> But that's just another RDF sentence/statement constructed from blank
>>>> nodes (indefinite pronouns): 
>>>> @prefix : <#> . 
>>>> [ a foaf:Person; foaf:name "Alice"] :claims [a foaf:Person; foaf:name
>>>> "Bob"; foaf:age "23"^^xsd:integer] . 
>> [...]
>> It states that a Person named "Alice" :claims a Person named "Bob" has
>> age 23 expressed as in integer.
> I disagree. It states that a Person named "Alice" :claims something and
> this something is of rdf:type foaf:Person. So, what she is claiming is a
> person rather than being about a person.

I hope you are not interpreting :clams somewhat whimsically, since I
didn't actually assert that the rdfs:range of :claims is an
rdf:Statement instance in my original example sentence. I could have
written my example as follows, to be more precise:

@prefix : <#> . 

:claims a rdf:Property ;
        rdfs:range owl:Thing . 

[ a foaf:Person; foaf:name "Alice"] :claims [a foaf:Person; foaf:name
"Bob"; foaf:age "23"^^xsd:integer] . 

If on the other hand I had stated:

@prefix : <#> . 

:claims a rdf:Property ;
        rdfs:range owl:Thing . 

[ a foaf:Person; foaf:name "Alice"] :claims [a foaf:Person; foaf:name
"Bob"; foaf:age "23"^^xsd:integer] . 

Then I would be articulating what you assumed, and my sentence would then be incorrect :)

BTW -- I can also do all of this in a document (as per SPARQL Named
Graphs) and just pepper the document with additional metadata for
provenance purposes. Basically, why aren't  SPARQL Named Graphs a viable
solution to this problem i.e., RDF stays as is for data definition while
languages such as SPARQL handle operations on RDF structured data?

>> [...]
>>> I guess what you actually wanted to write was something
>>> like the following:
>>> [ a foaf:Person; foaf:name "Alice"]
>>>            :claims [ a rdf:Statement ;
>>>                      rdf:subject   :Bob ;
>>>                      rdf:predicate foaf:age ;
>>>                      rdf:object    "23"^^xsd:integer ] . 
>> No, that is just a reified version of my initial statement.
> Are you saying that you consider the set of triples serialized as this
> piece of Turtle to be semantically equivalent to the set of triples
> serialized in the piece of Turtle above?

Of course not.


>> [...]
>>> By the definition of the RDF* data model, every RDF graph is an RDF*
>>> graph. Additionally, by the definition of the RDF*-to-RDF mapping, every
>>> RDF* graph can be viewed as an RDF graph.
>> Sorta, but this is serious work to be done explaining all of this in a
>> manner that prevents the confusion I fear.
> Point taken.
> Olaf


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Received on Wednesday, 14 August 2019 15:01:48 UTC

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