JSON-LD-star patterns

The JSON-LD CG (specifically, Pierre-Antoine, Niklas and myself) started a draft on JSON-LD-star [1] in 2020. Since then, the target has changed, so we’ve created an issue to consider how this might adapt to Triple Terms, Reifying Triples, and Annotations [2].

Basically, the idea is to add three new keywords to JSON-LD, @reifies, @triple, and @annotation. JSON-LD encodes RDF iin JSON using Node Objects, which can represent a subject/identifier, @type and properties based on key/value entries in a map. This proposal uses @reifies, @triple, and @annotation as special properties to encode triple terms.

At the most fundamental level, @triple is intended to encode a single triple with an @id and a single-valued property.

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/",
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
  },
  "rdf:reifies": {
    "@triple": {
      "@id": "bob",
      "age": 42
    }
  },
  "certainty": 0.8
}

This would be equivalent to the following Turtle:

BASE <http://example.org/>
PREFIX : <http://example.org/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#”>

[ rdf:reifies <<( :bob :age 42 ))> ]; :certainty: 0.8 .

In this case, since there is no explicit @id at the top level, a blank node is generated, which is used as the reifier.

The @reifies keyword can be used to compact this, and holds the potentially for reifying more than one triple:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/",
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
  },
  “@id”: “reifier”,
  "@reifies": {
    "@id": "bob",
    "age": 42
  },
  "certainty": 0.8
}

The example shows a single triple, but in principle, @reifies could take an array of objects, each with a different @id, and each object may have one or more properties; each of these could turn into a separate triple term referenced by the same reifier. This perticular example uses an expicit reifier, so the resulting Turtle would be:

BASE <http://example.org/>
PREFIX : <http://example.org/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#”>

:reifier rdf:reifies <<( :bob :age 42 ))>; :certainty: 0.8 .

It’s an open question if downstream relationships would also be reified; they’re not in Turtle.

The annotation syntax is similar to Turtle:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/"
  },
  "@id": "bob",
  "age": {
    "@value": 42,
    "@annotation": {
      "@id": "_:anno",
      "certainty": 0.8
    }
  }
}

In this case, the annotation may have it’s own reifier assigned (here ’s _:anno), or one can be assigned automatically. This would be equivalent to the following Turtle:

:bob :age 42 ~ _:anno {| :certainty  8.0E-1 |} .

Note that in the Reification example, the @refiies keyword acts much like @graph. If it were restated as follows, it would use the named graph syntax, which is common in Verifiable Claims.

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/",
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  },
  "@id": "reifier",
  "@graph": {
    "@id": "bob",
    "age": 42
  },
  "certainty": 0.8
}

This results in the following TriG.

BASE <http://example.org/>
PREFIX : <http://example.org/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#”>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> .

:reifier :certainty 8.0E-1 .

:reifier {
  :bob :age 42 .
}

This suggests that there may be a way to describe named graphs using reification.

Gregg Kellogg
gregg@greggkellogg.net

[1] https://json-ld.github.io/json-ld-star/
[2] https://github.com/json-ld/json-ld-star/issues/49

Received on Saturday, 14 September 2024 20:13:33 UTC