eyeprolog

RDF 1.2 nested triple terms

What is buried inside a claim about a claim?

An auditor reviews Alice’s claim that Bob knows Carol. In RDF 1.2 that is a triple term inside a triple term. EyeProlog matches the whole nesting with one pattern and recovers the innermost relationship.

Run it in the playground · Source

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The question

Which relationship sits at the bottom of a review of a claim?

This is one of a family of RDF 1.2 examples. RDF data arrives as rdf(Subject, Predicate, Object, Graph) facts, as produced by rdf-prolog-interchange, and results are printed in the same shape.

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The data

rdf(iri('https://example.org/auditor'), iri('https://example.org/reviews'), triple(iri('https://example.org/alice'), iri('https://example.org/claims'), triple(iri('https://example.org/bob'), iri('https://example.org/knows'), iri('https://example.org/carol'))), default_graph).

Triple terms nest: the auditor reviews a statement whose object is itself a statement. Each level is a statement about the one below it, and none of them is asserted as plain fact.

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The rule

result_rdf(S, iri('https://example.org/knows'), O, G) :-
  rdf(
    _,
    iri('https://example.org/reviews'),
    triple(
      _,
      iri('https://example.org/claims'),
      triple(S, iri('https://example.org/knows'), O)
    ),
    G
  ).

The pattern has the same shape as the data. Nesting needs no special query language: a nested term is matched by a nested pattern.

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The answer

eyeprolog examples/rdf12-nested-triple-term.pl

result_rdf(iri('https://example.org/bob'), iri('https://example.org/knows'), iri('https://example.org/carol'), default_graph).

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The reason

step(result_rdf(iri('https://example.org/bob'), iri('https://example.org/knows'), iri('https://example.org/carol'), default_graph),
     rule(2),
     ['S' = iri('https://example.org/bob'),
      'O' = iri('https://example.org/carol'),
      'G' = default_graph],
     [rdf(iri('https://example.org/auditor'), iri('https://example.org/reviews'), triple(iri('https://example.org/alice'), iri('https://example.org/claims'), triple(iri('https://example.org/bob'), iri('https://example.org/knows'), iri('https://example.org/carol'))), default_graph)]).

The proof cites the single reviewed triple. Who reviewed, who claimed, and what was claimed all stay visible in that one premise.

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The check

condition('C1', resolution, ok, 2).
condition('C4', coverage, ok, 2).
condition('C7', relevance, ok, 3).
trusted(0).
verdict(checked).

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Try it

• Also return who made the inner claim, as a second result relation.
• Add a review of a different claim and predict which of the two the rule picks up.
• Compare with the single-level triple term deck.

Learn more in The Art of EyeProlog, Chapter 9.

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