如何在JSON-LD中为RDF值编码数据类型IRI？

Question

A JSON-LD context can be used to specify the range of a property. Eg, the following stats that the range of rdf:value consists of integers:

{
  "@context": {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "xsd": "http://www.w3.org/2001/XMLSchema#",
    "rdf:value": { "@type": "xsd:integer" }
  },
  "rdf:value": "1"
}

​In RDF modeling it is common to use different ranges for different uses of rdf:value . Eg, the following expresses that an object costs €2,50 and has temperature 28.2 ℃ (using Turtle notation):

_:1 ex:price [ rdf:value "2.50"​^^xsd:decimal ; ex:unit ex:euros ] ;
    ex:temperature [ rdf:value "28.2"^^xsd:float ; ex:unit ex:degreesCelsius ] .

How do I describe this in terms of a JSON-LD context? It seems to me that I need property paths (borrowing a concept from SPARQL) as keys, specifically the following for the current example:

"ex:price/rdf:value": "xsd:decimal"
"ex:temperature/rdf:value": "xsd:float"

Is there a way to specify this in JSON-LD?

Answer 1

You can provide a typed value by specifying a value object .

Example:

{
  "@context": 
  {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "xsd": "http://www.w3.org/2001/XMLSchema#"
  },
  "rdf:value": 
  {
    "@value": "1",
    "@type": "xsd:integer"
  }
}

Answer 2

You can also nest @context to specialize/override properties. To take your example:

{
  "@context": {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "xsd": "http://www.w3.org/2001/XMLSchema#",
    "rdf:value": { "@type": "xsd:integexr" }
  },
  "rdf:value": "1",
  "ex:price": {
    "@context": {
      "rdf:value": { "@type": "xsd:float"}
    },
    "rdf:value": "35.3"
  },
  "ex:temperature": {
    "@context": {
      "rdf:value": { "@type": "xsd:decimal"}
    },
    "rdf:value": "2.50"
  }
}

You can experiment with this in the JSON-LD Playground .

Another approach is to use custom properties that all map to one @id ( rdf:value ) but with different datatypes:

{
  "@context": {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "xsd": "http://www.w3.org/2001/XMLSchema#",
    "value_integer": {
      "@id": "rdf:value",
      "@type": "xsd:integer"
    },
    "value_float": {
      "@id": "rdf:value",
      "@type": "xsd:float"
    },
    "value_decimal": {
      "@id": "rdf:value",
      "@type": "xsd:decimal"
    }
  },
  "value_integer": "1",
  "ex:price": {
    "value_decimal": "35.3"
  },
  "ex:temperature": {
    "value_float": "2.50"
  }
}

See this example on the JSON-LD playground .

Answer 3

The easiest way is to introduce separate properties. Something like (I also set @vocab to ex here):

{
  "@context": {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
    "xsd": "http://www.w3.org/2001/XMLSchema#",
    "price_value": { "@id": "rdf:value", "@type": "xsd:decimal" },
    "temperature_value": { "@id": "rdf:value", "@type": "xsd:float" },
    "@vocab": "http://ex.org/",
    "unit": { "@type": "@vocab" }
  },
  "price": {
    "price_value": "2.50",
    "unit": "euros"
  },
  "temperature": {
    "temperature_value": "28.2",
    "unit": "degreesCelsius"
  }
}