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Re: RDF* semantics

From: Olaf Hartig <olaf.hartig@liu.se>
Date: Wed, 7 Aug 2019 15:31:22 +0000
To: "public-rdf-star@w3.org" <public-rdf-star@w3.org>
CC: Kingsley Idehen <kidehen@openlinksw.com>
Message-ID: <1565191880.8060.204.camel@lille71.ida.liu.se>
On Wed, 2019-08-07 at 10:37 -0400, Kingsley Idehen wrote:
> On 8/7/19 5:13 AM, Olaf Hartig wrote:
> [...]
> > > > For instance, we my want to capture that Alice told us that Bob's 
> > > > age is 23, even if we don't have a document from Alice with this
> > > > statement/claim regarding Bob's age.
> > > Through what medium did Alice make the aforementioned claim about Bob?
> > As I wrote, she *told* us (during a conversation in a cafe, if you
> > like).
> 
> 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] . 
>
> Thus, it still retains the fundamental subject, predicate, object
> structure covered by terms in the RDF Vocabulary for describing the
> components of an rdf:Statement.

I think you made a mistake in this example. According to these triples,
what Alice claims is of type foaf:Person, has foaf:name "Bob", and
foaf:age 23. 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 ] . 

Using RDF* (assuming the SA mode I mention in my initial email in this
thread), we may write the same as follows.

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

Besides that mistake, I am totally fine with what you are saying; yes,
this communication may be delivered via a document.

> [...]
> > However, as an alternative to the syntactic-sugar perspective, another
> > perspective is to consider RDF* to be based on its own abstract data
> > model (which is an extension of the RDF data model).
> 
> An alternative abstract data model is certainly a cleaner approach,
> but that isn't really RDF anymore. Thus, RDF* would lead to confusion,
> IMHO.

Correct, it is not RDF anymore. But it is not something completely
different either. It is an extension of RDF.

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.

> >  Then, as has been
> > done for the RDF data model, we may define a semantics related to the
> > RDF* data model. Pat's initial point was that such a semantics will help
> > to provide some clarity (under this alternative perspective, I assume).
> 
> 
> I'll let Pat speak for himself :)

;-)

Olaf


Received on Wednesday, 7 August 2019 15:31:52 UTC

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