Re: What are the differences between a quoted triple and its singleton set?

Although there is a FPWD of RDF 1.2 Semantics, it does not contain any 
semantics for quoted triples as the semantics for quoted triples has not yet 
been determined by the RDF-star working group.

So the wording in RDF Semantics has not yet been adjusted to consider 
unasserted triples.  My view is that this the wording will be adjusted to 
cover only asserted triples, making your question moot.

(Note that a quoted triple is a triple occurring as the subject or object of 
another triple and may also appear as an asserted triple.   Careful 
distinctions may have to be made in RDF Semantics to keep everything straight.)

peter




On 5/27/23 08:34, Niklas Lindström wrote:
> Dear all,
> 
> Given that RDF Semantics (both in 1.1 [1] and 1.2 [2]) state:
> 
>      A triple is identified with the singleton set containing it, so
> that each triple in a graph is considered to be a subgraph.
> 
> Why, then, isn't a quoted triple, say:
> 
>      prefix dc: <http://purl.org/dc/terms/>
>      prefix : <http://example.org/ns/>
> 
>      << <http://example.net/s> :p "o" >> dc:date "2023" .
> 
> simply identical to:
> 
>      <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> dc:date "2023" .
>      graph <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> {
>          <http://example.net/s> :p "o" .
>      }
> 
> The one difference I can make is that it is not *explicit* that the
> singleton set above is not asserted. Rather, due to [3], it appears
> undefined, or user/application dependent(?). That might be amended by
> using reification, like:
> 
>      <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> dct:date "2023" .
>      <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> {
>          <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> a rdf:Statement ;
>              rdf:subject <s> ;
>              rdf:predicate :p ;
>              rdf:object "o" .
>      }
> 
> Or, perhaps better, it could be solved by defining a symbol for
> stating that a particular graph is not asserted, e.g.
> `blogic:NeutralGraph` (inspired by [4] and [5]), like:
> 
>      <data:application/n-triples,:%3Chttp%3A//example.net/s%3E%20%3Chttp%3A//example.org/ns/p%3E%20%22o%22%20.>
> a blogic:NeutralGraph .
> 
> I've tried to follow the history and ongoing work of RDF-star, and
> while I suspect the options above have been considered and rejected, I
> fail to grasp exactly why. Is it that since *just* singleton graphs
> are insufficient for the criteria of quoted triples, elaborating on it
> was not considered worthwhile? Or is it because of how quad stores
> work in practise? Perhaps, hidden behind this from the community
> report [6]:
> 
>      RDF-star describes quoted triples, which are not necessarily
> present in any named graph, or within the default graph.
> 
> lies a set of unresolved practical problems? E.g. that a graph
> containing quoted triples would have to relate to lots of singleton
> sets (graphs identified by a triple), and that these sets would need
> to be treated differently depending on their type and/or
> relationships? I may miss something obvious here, because to me,
> introducing a new kind of RDF "atom" just sidesteps that, instead of
> working to make more sense of the existing practises for named graphs,
> and in the process eliminating unnecessary differences (the divergence
> of quotation and named graphs), as well as illuminating, existing
> necessary ones (such as how named graphs can be used together in
> different ways).
> 
> Instead, RDF is being extended with the notion of a recursively
> defined "complex triple" (and might even have "levels of compliance"
> [7] with ensuing new differences [8]). This is quite a departure from
> what RDF has been for over 20 years, where hitherto everything has
> been possible to reduce to a simple, *flat* substrate of quads. I'm
> trying to understand why this is irrevocably necessary.
> 
> While I see many use cases for quoted triples (and for quotation in
> general), from my point of view they are *closely* related to the
> current practises of named graphs. I fail to see harmony with that in
> the evolving semantics. I don't see the necessary difference.
> 
> Best regards,
> Niklas
> 
> [1]: https://www.w3.org/TR/rdf11-mt/#notation-and-terminology
> [2]: https://w3c.github.io/rdf-semantics/spec/#notation
> [3]: https://www.w3.org/TR/rdf11-datasets/#each-named-graph-defines-its-own-context
> [4]: https://www.w3.org/2009/07/NamedGraph.html#named-graphs
> [5]: https://www.slideshare.net/PatHayes/blogic-iswc-2009-invited-talk
> [6]: https://w3c.github.io/rdf-star/cg-spec/2021-12-17.html#trig-star
> [7]: https://github.com/w3c/rdf-star-wg/issues/19
> [8]: https://github.com/w3c/rdf-star-wg/issues/33
>

Received on Saturday, 27 May 2023 12:45:39 UTC