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Re: RDF* semantics

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Fri, 30 Aug 2019 15:50:48 -0400
To: public-rdf-star@w3.org
Message-ID: <350ed7b8-98eb-9e09-55ed-2e1f3bb3fc9a@openlinksw.com>
On 8/30/19 3:12 PM, Olaf Hartig wrote:
> Kingsley,
>
> On fredag 30 augusti 2019 kl. 12:13:27 CEST Kingsley Idehen wrote:
>> On 8/30/19 11:36 AM, Olaf Hartig wrote:
>>> [...]
>>> Note that the last five lines part of your document (the part that uses
>>> RDF
>>> reification) can be written more concisely in Turtle* as follows (assuming
>>> RDF* is used in SA mode):
>>>
>>> Alice:  :describes << Bob: foaf:age "23"^^xsd:integer >> .
>>>
>>> Thanks,
>>> Olaf
>> You are saying that in RDF* you would like the following snippet to
>> become RDF-Turtle notation, which isn't the case today:
>>
>> Alice:  :describes << Bob: foaf:age "23"^^xsd:integer >> .
>  
> There already exists a serialization format called Turtle* that is a syntactic 
> extension of RDF-Turtle and in this format you can write such snippets. For 
> the definition of this format see Section 3.3 in the document at:
> http://arxiv.org/pdf/1406.3399


Turtle* and RDF-Turtle are two different things, as denoted. I was
referring to the latter :)

Additional responses below .

>  
>> Here's a fixed version of my example. I've rebased identifiers for Alice
>> and Bob using an indexical
>> <https://www.lexico.com/en/definition/indexical#this> relative to
>> document (context provider)  (as per my very first example).
>>
>> ## Turtle Start ##
>>
>> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
>> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
>> @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
>> @prefix foaf: <http://xmlns.com/foaf/0.1/> .
>> @prefix : <#> .
>>
>> <> a foaf:Document .
>> <> foaf:name "Document about Alice"@en .
>> <> foaf:primaryTopic :Alice .
>>
>> :Alice  rdf:type  foaf:Person .
>> :Alice  foaf:name  "Alice" .
>> :
>> :Bob  rdf:type  foaf:Person .
>> :Bob  foaf:name  "Bob" .
>> :Bob  foaf:age "23"^^xsd:integer .
>>
>> # Context clarity regarding :claims relation
>>
>> :claims a rdf:Property .
>> :claims rdfs:domain foaf:Person .
>> :claims rdfs:range rdf:Statement .
>>
>> # Olaf would like the following to as syntax-sugar (*rather than change to
>> existing RDF semantics*): # :Alice :claims << :Bob foaf:age
>> "23"^^xsd:integer >> .
>> # for what follows
>>
>> :Alice  :claims  [ a rdf:Statement;
>>
>>                      rdf:subject :Bob ;
>>                      rdf:predicate foaf:age ;
>>                      rdf:object "23"^^xsd:integer
>>                   ] .
>>
>> ## Turtle End ##
> Yes.
>
> Now, notice that the :claims property you are using here is different from the 
> :claims property as used in your earlier examples. That is, your earlier 
> examples used the :claims property as if it was defined as follows:
>
> :claims a rdf:Property .
> :claims rdfs:domain foaf:Person .
> :claims rdfs:range foaf:Person .
>
> -Olaf
>

We can't simply assume that :claim denotes an rdf:Property that has
range rdf:Statement. Basically, to speak about any rdf:Property instance
we have to be clear about its rdfs:domain and rdfs:range for appropriate
context.

Remember in an earlier mail I stated:

...

Here's are document URL that includes content representing what Olaf and
I are discussing, using RDF-Turtle notation or Nanotation (i.e,
"text/plain" file that's readable as is or via our OSDS Browser
Extension
<https://chrome.google.com/webstore/detail/openlink-structured-data/egdaiaihbdoiibopledjahjaihbmjhdj?hl=en#this>for
visualization):

My original statements in documents without reification :

1. 
https://kingsley.idehen.net/public_home/kidehen/Public/Linked%20Data%20Documents/Tutorials/label-property-graph-stuff/alice-claims-about-bob.txt
-- RDF-Turtle Nanotation in plain text (i.e., "text/plain" content-type)

2.
https://kingsley.idehen.net/public_home/kidehen/Public/Linked%20Data%20Documents/Tutorials/label-property-graph-stuff/alice-claims-about-bob.ttl
-- RDF-Turtle (i.e., "text/turtle" content-type)


Documents comprising reified statements (as per what Olaf is speaking
about primarily) using terms from the RDF Vocabulary
<http://www.w3.org/1999/02/22-rdf-syntax-ns#>:

1.
https://kingsley.idehen.net/public_home/kidehen/Public/Linked%20Data%20Documents/Tutorials/label-property-graph-stuff/alice-claims-about-bob-reified.txt
-- RDF-Turtle Nanotation in plain text (i.e., "text/plain" content-type)

2.
https://kingsley.idehen.net/public_home/kidehen/Public/Linked%20Data%20Documents/Tutorials/label-property-graph-stuff/alice-claims-about-bob-reified.ttl
-- RDF-Turtle Nanotation in plain text (i.e., "text/plain" content-type)

As I see it, the issue we are debating is primarily about reification
and syntax sugar for articulation convenience i.e., does this actually
constitute what's denoted as RDF* Semantics (for which I am currently
unconvinced, bearing in mind what exists regarding the roles of RDF
[DDL] and SPARQL [DML] which offers Named Graphs as a solution).

-- 
Regards,

Kingsley Idehen	      
Founder & CEO 
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Received on Friday, 30 August 2019 19:51:15 UTC

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