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Re: RDF* semantics

From: Gregg Kellogg <gregg@greggkellogg.net>
Date: Sat, 17 Aug 2019 15:27:39 -0700
Cc: Kingsley Idehen <kidehen@openlinksw.com>, public-rdf-star@w3.org
Message-Id: <1C41FC24-D2D4-4DE7-8FF5-58015446DA98@greggkellogg.net>
To: Martynas Jusevičius <martynas@atomgraph.com>
On Aug 17, 2019, at 1:18 PM, Martynas Jusevičius <martynas@atomgraph.com> wrote:
> 
> Yes the syntax was more of an "abstract" example.
> 
> OK, I guess it makes more sense with rdf:Statement.
> 
> I don't have more to add as I haven't really studied the RDF* semantics :)
> 
>> On Sat, Aug 17, 2019 at 8:45 PM Kingsley Idehen <kidehen@openlinksw.com> wrote:
>> 
>> On 8/17/19 12:19 PM, Martynas Jusevičius wrote:
>> 
>> Kingsley,
>> 
>> don't you mean
>> 
>> [ a foaf:Person; foaf:name "Alice"] :claims { [a foaf:Person;
>> foaf:name "Bob"; foaf:age "23"^^xsd:integer] . } .
>> 
>> Note the graph designation.

This makes sense as Notation-3, which is well suited to making statements about graphs. It could be interpreted as RDF by using an intermediate BNode, which would be similar to the rdf:Statement, except that the quoted triples are not part of the default graph.

Gregg

>> Not as presented syntactically as that isn't RDF-Turtle notation.
>> 
>> 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 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:
>> 
>> 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).
>> 
>> 
>> Kingsley
>> 
>> 
>> 
>> On Wed, Aug 14, 2019 at 5:02 PM Kingsley Idehen <kidehen@openlinksw.com> wrote:
>> 
>> 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.
>> 
>> 
>> Kingsley
>> 
>> [...]
>> 
>> 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
>> 
>> 
>> 
>> --
>> Regards,
>> 
>> Kingsley Idehen
>> Founder & CEO
>> OpenLink Software
>> Home Page: http://www.openlinksw.com
>> Community Support: https://community.openlinksw.com
>> Weblogs (Blogs):
>> Company Blog: https://medium.com/openlink-software-blog
>> Virtuoso Blog: https://medium.com/virtuoso-blog
>> Data Access Drivers Blog: https://medium.com/openlink-odbc-jdbc-ado-net-data-access-drivers
>> 
>> Personal Weblogs (Blogs):
>> Medium Blog: https://medium.com/@kidehen
>> Legacy Blogs: http://www.openlinksw.com/blog/~kidehen/
>>              http://kidehen.blogspot.com
>> 
>> Profile Pages:
>> Pinterest: https://www.pinterest.com/kidehen/
>> Quora: https://www.quora.com/profile/Kingsley-Uyi-Idehen
>> Twitter: https://twitter.com/kidehen
>> Google+: https://plus.google.com/+KingsleyIdehen/about
>> LinkedIn: http://www.linkedin.com/in/kidehen
>> 
>> Web Identities (WebID):
>> Personal: http://kingsley.idehen.net/public_home/kidehen/profile.ttl#i
>>        : http://id.myopenlink.net/DAV/home/KingsleyUyiIdehen/Public/kingsley.ttl#this
>> 
>> 
>> 
>> 
>> --
>> Regards,
>> 
>> Kingsley Idehen
>> Founder & CEO
>> OpenLink Software
>> Home Page: http://www.openlinksw.com
>> Community Support: https://community.openlinksw.com
>> Weblogs (Blogs):
>> Company Blog: https://medium.com/openlink-software-blog
>> Virtuoso Blog: https://medium.com/virtuoso-blog
>> Data Access Drivers Blog: https://medium.com/openlink-odbc-jdbc-ado-net-data-access-drivers
>> 
>> Personal Weblogs (Blogs):
>> Medium Blog: https://medium.com/@kidehen
>> Legacy Blogs: http://www.openlinksw.com/blog/~kidehen/
>>              http://kidehen.blogspot.com
>> 
>> Profile Pages:
>> Pinterest: https://www.pinterest.com/kidehen/
>> Quora: https://www.quora.com/profile/Kingsley-Uyi-Idehen
>> Twitter: https://twitter.com/kidehen
>> Google+: https://plus.google.com/+KingsleyIdehen/about
>> LinkedIn: http://www.linkedin.com/in/kidehen
>> 
>> Web Identities (WebID):
>> Personal: http://kingsley.idehen.net/public_home/kidehen/profile.ttl#i
>>        : http://id.myopenlink.net/DAV/home/KingsleyUyiIdehen/Public/kingsley.ttl#this
>> 
> 
Received on Saturday, 17 August 2019 22:28:06 UTC

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