RDF star and LPGs

RDF-star and LPGs (DRAFT 2024.07.19)

CREATE (a1:Account {accountNumber: 1})
CREATE (a2:Account {accountNumber: 2})
CREATE (a3:Account {accountNumber: 3})

CREATE (a1)-[:TRANSACTION {amount: 1000, currency: "gbp", date: "2002-09-24Z"}]->(a2)
CREATE (a2)-[:TRANSACTION {amount: 900, currency: "gbp", date: "2002-10-03Z"}]->(a3)

<-->

:a1 a :Account ; 
  :accountNumber 1 .
:a2 a :Account ;
  :accountNumber 2 .
:a3 a :Account ;
  :accountNumber 3 .

<< :e1 | :a1 :TRANSACTION :a2 >>
  :amount 1000 ;
  :currency "gbp" ;
  :date "2002-09-24Z"^^xsd:date .
  
<< :e2 | :a2 :TRANSACTION :a3 >>
  :amount 900 ;
  :currency "gbp" ;
  :date "2002-10-03Z"^^xsd:date .

OBSERVATIONS:

• Node identifiers, node labels, edge identifiers, and edge labels are denoted by IRIs.

• Keys are denoted by IRIs, and values are denoted by literals.

• Triple terms have transparent semantics.

• Triple terms involve node identifiers as subject and object and an edge label as property.

• Reifiers denote edge identifiers.

IN THIS SCENARIO, the ONLY simple entailments involving triple terms are due to the bnode abstraction rule of simple entailment. E.g., the following is entailed:

:e1 rdf:reifies <<(_:n1 :TRANSACTION _:n2)>> .
:e1 :amount _:v1 ;

These entailments can be considered as harmless in this scenario; e.g., by discarding any triple with a triple term involving bnodes.

Another case would be the entailment:

_:g1 rdf:reifies <<(:a1 :TRANSACTION :a2)>> .
_:g1 :amount 900 ;

which introduces a new edge identifier _:g1 for the existing edge originally identified by :e1. Note that all the entailments in which the new edge identifier _:g1 is involved are exactly the same the ones in which the original edge identifier :e1 is involved. These entailments can be considered as harmless in this scenario; e.g., by discarding all the duplicate triples with bnodes.

Note that the above entailments are the only ones involving bnodes as edge identifiers, so that a bnode denoting an edge identifier will never be associated to any other edge. Therefore, "functionality" of rdf:reifies is always implicitly satisfied in this scenario.

Finally, the LPG data encoded in RDF as above can be extended, without changing the base encoding, by adding more RDFS, SHACL, OWL schema information.