diff --git a/cg-spec/editors_draft.html b/cg-spec/editors_draft.html index 7a22ed4c..5aac635f 100644 --- a/cg-spec/editors_draft.html +++ b/cg-spec/editors_draft.html @@ -346,6 +346,8 @@

Overview

`rdfs:``<http://www.w3.org/2000/01/rdf-schema#>` `owl:``<http://www.w3.org/2002/07/owl#>` `prov:``<http://www.w3.org/ns/prov#>` +`dbo:``<http://dbpedia.org/ontology/>` +`dbr:``<http://dbpedia.org/resource/>` `dc:``<http://purl.org/dc/elements/1.1/>` `dct:``<http://purl.org/dc/terms/>` @@ -2820,11 +2822,11 @@

Mapping RDF-star abstract syntax to RDF

    -
  1. For each IRI |i| in the constituents of |G| starting with `https://w3c.github.io/rdf-star/unstar#`:
      +
    1. For each IRI |i| in the constituents of |G| starting with `https://w3c.github.io/rdf-star/unstar#`:
      1. Mint a new IRI |j| by appending an underscore (`_`) to |i|.
      2. Replace with |j| all occurrences of |i| in the subject, predicate, or object position of an asserted or quoted triple of |G|.
      2. -
    2. While |G| contains quoted triples:
        +
      1. While |G| contains quoted triples:
        1. Pick an RDF-star triple (|s|, |p|, |o|) in the constituents of |G| such that neither |s| nor |o| is a quoted triple.
        2. Mint a fresh blank node |b| (i.e., such that |b| is not in the constituents of |G|).
        3. Replace with |b| all occurrences of (|s|, |p|, |o|) in the subject or object position of an asserted or quoted triple of |G|.
          4. @@ -2974,26 +2976,26 @@

          Referential opacity

          -

          Note that the current semantics does not forbid the additional inferences to be drawn. However, they would require additional knowledge and an appropriate semantic extension, not specified in this document. This makes RDF-star less readily usable for (but not incompatible with) that latter kind of use-cases.

          +

          Note that the current semantics does not forbid the additional inferences to be drawn. However, they would require additional knowledge and an appropriate semantic extension (such as the one discussed in ). This makes RDF-star less readily usable for (but not incompatible with) that latter kind of use-cases.

          @@ -3031,11 +3033,102 @@

          Alternatives to referential opacity

          +
          Other design choices for the semantics have also been discussed by the community group; these have been summarized in a Github issue.
          + - +
          +

          Selective referential transparency

          + +

          Since the needs for referential opacity and transparency are use-case dependent (as discussed above), it may make sense for different predicates to have different behaviors. Consider the following example.

          + + 
          +        
+
          + +

          One could argue that the candidate entailment #1 is desirable because the property `:on` is understood to be about the statement made by the subject triple (that statement was true on the given date, regardless of its RDF expression). On the other hand, the candidate entailment #2 may be considered not desirable because the predicate `:source` is about the triple itself (that specific triple was parsed from the given Turtle file).

          -
          Other design choices for the semantics have also been discussed by the community group; these have been summarized in a Github issue.
          +

          Subclasses of `rdf:Property` could therefore be defined to identify properties that imply referential transparency on their subject triple, on their object triple, or on both. Note, however, that the group has not reached consensus on the definition or usefulness of such a vocabulary.

          + +

          Here is a sketch of how to extend the semantics in a way that it can work with such a property, which we call a transparency-enabling property (TEP). The basis of the idea is that each such property |p| is identified by adding to the RDF-star graph a triple of the form (|p|, `rdf:type`, `rdf-star:TransparencyEnablingProperty`); i.e., for the previous example, this triple would be (`:on`, `rdf:type`, `rdf-star:TransparencyEnablingProperty`). Notice that enabling referential transparency based on such TEPs is only local to the RDF-star graph(s) in which the TEP is stated to be a TEP (or where this statement can be inferred as per the entailment regime considered); in other words, for every graph |G| in which a property is not stated to be transparency enabling, all quoted triples within triples in |G| that have the property as predicate are considered as referentially opaque, even if there may exist some other graph in which the property is stated to be transparency enabling. + The semantics of such TEPs can be captured for the different entailment regimes by extending the corresponding notion of interpretation as exemplified in the following for the simple interpretation of the simple entailment regime.

          + +

          A simple TEP-interpretation is a simple interpretation |I| that satisfies the following two additional conditions:

          + +
            +
          1. Ensure that, for all quoted triples in this interpretation, all "equivalent" triples also exist in the interpretation. +
              +
            • For all |t|, |s|, |p|, |o| in the domain IR such that
                +
              • (|t|, |s|) ∈ IEXT(`unstar:subject`), +
              • (|t|, |p|) ∈ IEXT(`unstar:predicate`), +
              • (|t|, |o|) ∈ IEXT(`unstar:object`), +
              +
            • and for all terms |s|', |p|', and |o|' such that
                +
              • |I|(|s|') = |s|, +
              • |I|(|p|') = |p|, +
              • |I|(|o|') = |o|, +
              +
            • there must exist |t|' in IR such that
                +
              • (|t|', |s|) ∈ IEXT(`unstar:subject`), +
              • (|t|', |p|) ∈ IEXT(`unstar:predicate`), +
              • (|t|', |o|) ∈ IEXT(`unstar:object`), +
              • (|t|', |I|(L(|s|'))) ∈ IEXT(`unstar:subjectLexical`), +
              • (|t|', |I|(L(|p|'))) ∈ IEXT(`unstar:predicateLexical`), and +
              • (|t|', |I|(L(|o|'))) ∈ IEXT(`unstar:objectLexical`). +
              +
            + +
          2. Ensure that TEPs that hold for a triple also hold for all "equivalent" triples. +
            For every |p| such that (|p|,IS(`rdf-star:TransparencyEnablingProperty`)) ∈ IEXT(IS(`rdf:type`))
              +
            • |p| must be an element of IP +
            • For all |t|, |u|, |s|', |p|', |o|', |t|' in IR such that
                +
              • (|t|, |u|) ∈ IEXT(`p`) +
              • (|t|, |s|') ∈ IEXT(`unstar:subject`), +
              • (|t|, |p|') ∈ IEXT(`unstar:predicate`), +
              • (|t|, |o|') ∈ IEXT(`unstar:object`), +
              • (|t|', |s|') ∈ IEXT(`unstar:subject`), +
              • (|t|', |p|') ∈ IEXT(`unstar:predicate`), +
              • (|t|', |o|') ∈ IEXT(`unstar:object`) +
              + then (|t|', |u|) must also be an element of IEXT(|p|). +
            • For all |t|, |u|, |s|', |p|', |o|', |t|' in IR such that
                +
              • (|u|, |t|) ∈ IEXT(`p`) +
              • (|t|, |s|') ∈ IEXT(`unstar:subject`), +
              • (|t|, |p|') ∈ IEXT(`unstar:predicate`), +
              • (|t|, |o|') ∈ IEXT(`unstar:object`), +
              • (|t|', |s|') ∈ IEXT(`unstar:subject`), +
              • (|t|', |p|') ∈ IEXT(`unstar:predicate`), +
              • (|t|', |o|') ∈ IEXT(`unstar:object`) +
              + then (|u|, |t|') must also be an element of IEXT(|p|). +
            +
          + +

          Given two RDF-star graphs |G| and |H|, and following standard terminology, we say that a simple TEP-interpretation |I| satisfies |G| if |I|(|G|) = true, and that |G| is (simply) TEP-satisfiable if a simple TEP-interpretation exists that satisfies |G|; otherwise, |G| is (simply) TEP-unsatisfiable. We say that |G| simply TEP-entails |H| if every simple TEP-interpretation that satisfies |G| also satisfies |H|. If |G| and |H| each TEP-entail the other, they are TEP-equivalent.

          + +

          TEP-entailment is defined here as an extension of simple entailment, but other entailment regimes (such as RDF entailment or RDFS entailment) can be extended in the exact same way (i.e., by extending their respective notion of interpretation with the aforementioned two conditions).

          + +
          + +