Re: RDF* and grouping relation properties

As far as I can tell (but I haven't read everything about RDF*) it is
unclear whether in the result of your syntax it is not possible to
determine which source associates with which retrieval.   In RDF
reificiation the answer is obvious - yes - but I don't know how RDF*
handles multiple occurences of the same triple inside <<>>.

Does anyone have a pointer to a document that could be considered as
clearing this up?  That is, the document must be close to official and
also provide a clear semantics for RDF*.



But as far as Tim's point goes, there is quite often a need for
explicitly representing this entity in the world.  Simple encodings of
the world often break when one moves away from the simplest part of it.

peter




On Thu, 2020-06-18 at 11:44 -0400, Tim Finin wrote:
> While experimenting with RDF* I realized one issue: for some
> relations, we may have several properties that should be treated as a
> group.  For example, the provenance of a relation extracted from the
> text of a web page might include a link to the page and the date
> retrieved.
> 
> Using the following two RDF* expressions merges the four properties
> so that we can no longer determine which :source and :retrieved
> values go together.
> 
> > << :man :hasSpouse :woman >>
> >     :source <http://foo.com/>;;
> >     :retrieved "2020-06-17"^^xsd:date .
> > << :man :hasSpouse :woman >>
> >     :source <http://bar.com/>;;
> >     :retrieved "2020-01-01"^^xsd:date .
> 
> Using a traditional RDF reification approach maintains the pairing.
> 
> > :man2 :hasSpouse :woman2 .
> > [ ]  a rdf:Statement ;
> >      rdf:subject :man2 ;
> >      rdf:predicate :hasSpouse ;
> >      rdf:object :woman2 ;
> >     :source <http://foo.com/> ;
> >     :retrieved "2020-06-17"^^xsd:date .
> > [ ] a rdf:Statement ;
> >     rdf:subject :man2 ;
> >     rdf:predicate :hasSpouse ;
> >     rdf:object :woman2 ;
> >    :source <http://bar.com/>;;
> >    :retrieved "2020-01-01"^^xsd:date .
> 
> A possible solution when using RDF* is to encapsulate associated
> properties as a blank node entity, as in the following
> 
> > :man3 :hasSpouse :woman3 .
> > << :man3 :hasSpouse :woman3 >>
> >     :provenance [ :source <http://foo.com/>;;
> >                            :retrieved "2020-06-17"^^xsd:date ] .
> > << :man3 :hasSpouse :woman3 >>
> >     :provenance [ :source <http://bar.com/>;;
> >                            :retrieved "2020-01-01"^^xsd:date ] .
> 
> However, this approach seems to violate the normal key/value pattern
> of property graph properties, which could be a compatibility issue.
> 
> 
> --
> Tim Finin,  Willard and Lillian Hackerman Chair in Engineering, 
> Computer Science and
> Electrical Engineering, U. Maryland, Baltimore County, 1000 Hilltop
> Circle, Baltimore MD
> 21250. http://umbc.edu/~finin, finin@umbc.edu, tfinin@gmail.com, mobi
> le:410-499-3522

Received on Thursday, 18 June 2020 16:55:56 UTC