explain the context attribute

[jamesscottbrown]

No description provided.

[rpgoldman]

I don't think that description for context can be correct. For example, asking for a set of instances, I get

{
  "@id": "https://sift.net/container-ontology/container-ontology#Plate",
  "hasInstance": <....>,
  "@context": "https://owlery.phenoscape.org/json/context.jsonld"
}

I really don't know what that @context field is supposed to be.

[jamesscottbrown]

I don't think that description for context can be correct.

Why not? I think it is consistent with the response.

If I fetch the URL https://owlery.phenoscape.org/json/context.jsonld, the response is:

{
  "@context": {
    "equivalentClass": {
      "@id": "http://www.w3.org/2002/07/owl#equivalentClass",
      "@type": "@id"
    },
    "subClassOf": {
      "@id": "http://www.w3.org/2000/01/rdf-schema#subClassOf",
      "@type": "@id"
    },
    "superClassOf": {
      "@reverse": "http://www.w3.org/2000/01/rdf-schema#subClassOf",
      "@type": "@id"
    },
    "type": "@type",
    "hasInstance": {
      "@reverse": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type",
      "@type": "@id"
    },
    "isSatisfiable": {
      "@id": "http://purl.org/phenoscape/owlery.owl#isSatisfiable",
      "@type": "http://www.w3.org/2001/XMLSchema#boolean"
    },
    "value": {
      "@id": "http://www.w3.org/1999/02/22-rdf-syntax-ns#value"
    },
    "version": {
      "@id": "http://www.w3.org/2002/07/owl#versionIRI",
      "@type": "@id"
    },
    "imports": {
      "@id": "http://www.w3.org/2002/07/owl#imports",
      "@type": "@id"
    }
  }
}

Within this, the hasInstance attribute has the value:

 {
      "@reverse": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type",
      "@type": "@id"
}

Fetching http://www.w3.org/1999/02/22-rdf-syntax-ns#type, I see it is defined as:

rdf:type a rdf:Property ;
	rdfs:isDefinedBy <http://www.w3.org/1999/02/22-rdf-syntax-ns#> ;
	rdfs:label "type" ;
	rdfs:comment "The subject is an instance of a class." ;
	rdfs:range rdfs:Class ;
	rdfs:domain rdfs:Resource .

So it seems that the context.jsonld file is defining hasInstance (in the context of the API's repsonse) to be the reverse of rdf:type (which is defined as "The subject is an instance of a class.").

In other words, this is saying that that x hasInstance y means that y is an instance of class x. This seems to be consistent with the API response: the hasInstance attribute of the response contains a list of things which are instances of container-ontology:Plate - i.e., things which are of type container-ontology:Plate.

[jamesscottbrown]

This is a similar example in the JSON-LD spec: https://json-ld.org/spec/latest/json-ld/#example-55-using-reverse-to-define-reverse-properties

[rpgoldman]

OK, I think I see: @context is a JSON LD thing. The context it provides is something like a namespace import. It tells us how to interpret the use of the property "hasInstance" that appears in the query response without a namespace IRI.