Re: PG mode and SA mode

> On Sep 20, 2019, at 3:56 AM, Olaf Hartig <olaf.hartig@liu.se> wrote:
> 
> Pat,
> 
> On Wed, 2019-09-18 at 15:01 -0700, Patrick J Hayes wrote:
>>> On Sep 18, 2019, at 11:53 AM, Olaf Hartig <olaf.hartig@liu.se>
>>> wrote:
>>> [...]
>>> In contrast, if RDF* is used in PG mode, our example RDF* triple
>>> t would have to be converted into the following set of RDF
>>> triples, which contains one additional triple (namely, the last
>>> one in the following list):
>>> 
>>> (b, rdf:type, rdf:Statement)
>>> (b, rdf:subject, s)
>>> (b, rdf:predicate, p)
>>> (b, rdf:object, o)
>>> (b, p2, o2)
>>> (s, p, o)
>> 
>> What, in this graph, identifies the bnode b with the last triple? In
>> fact, why is it a bnode at all? Surely in this case, the subject of
>> the reification triples should be an IRI which identifies/names the
>> triple? But then how does this name get attached to its referent? It
>> seems like we need some kind of naming convention here, something
>> like
>> 
>> i: (s, p, o)
>> (:i, p2, o2)
> 
> Okay, I could have used an IRI instead of a bnode in this example. Yet,
> as you also point out, simply using an IRI in the reification triples
> is not an answer to the latter question you are asking here. However, I
> don't think that this is an issue of RDF*, but of the standard RDF
> reification approach.

I entirely agree. It has been obvious to me since 2001 that RDF reification gives no way to ‘link’ a reification description to the triple it puports to describe. I made several attempts to get this clarified in the RDF semantics, but the best I could manage to get through the WG was to have this entire matter made non-normative. (This also accounts for my early enthusiasm for named graphs, by the way. )

> 
> In fact, in RDF* there is no need for such a naming convention because,
> when talking about a triple t'=(s,p,o) in some other triple t, the idea
> of RDF* is to directly use the triple t' itself instead of using a name
> for that triple.
> 
> t = ( (s,p,o), p2, o2 )

I understand, and agree. But this does mean that your often-repeated claim to somehow reduce RDF* to RDF reification is not accurate. RDF* is a genuine extension to RDF.

Pat

> 
> Olaf
> 
>> Pat Hayes