Generate a JSON schema

JSON Schema document generation algorithm

The algorithm follow these steps to generate the JSON Schema:

Constant declarations

• A declaration is always added for @context since we are targeting JSON-LD
• schema version is always set to https://json-schema.org/draft/2020-12/schema
• a container_language declaration is always added with a patternProperty declaration with properties being language codes to deal with "@container": "language" properties.

Schema header

• title is populated from an owl:Ontology dct:title or rdfs:label
• version is populated from an owl:Ontology owl:versionInfo
• description is populated from an owl:Ontology dct:description

Node shapes conversion

Each node shape with at least one non-deactivated property shape is turned into an object schema in the $defs section of the schema, with the URI local name as the name of the schema. Node shapes with no non-deactivated property shapes are turned into string schemas being simple iri-reference.

• title is populated from the node shape rdfs:label
• description is populated from the node shape rdfs:comment
• There is always a required id property
• If node shape is closed, then additionalProperties is set to false
• Then each property shape is processed as described below

Property shapes conversion

Non-deactivated property shapes are processed this way:

• The corresponding JSON key is read from shacl-play:shortName annotation, otherwise the local name of the property in sh:path is used as the JSON key
• title is populated from the property shape sh:name
• description is populated from the property shape sh:description
• The property shape is mapped to a schema this way:
  • If the property shape has an sh:hasValue, a const schema is created with the value
  • If the property shape has an sh:in, an enum schema is created with the list of possible values
  • If the property shape has an sh:node, then :
    • If the property shape is annotated with shacl-play:embed shacl-play:EmbedNever, then a string schema with format iri-reference is generated
    • Otherwise, create a $ref schema with a reference to one of the schemas in the #/$defs section
    • If there is no sh:maxCount or a sh:maxCount that is > 1, then wrap the generated schema into an array schema
  • If the property shape has an sh:pattern, then turn it into a string schema with a pattern constraint.
  • If the property shape has an sh:datatype (with a consistent value for the same property across the SHACL spec), then:
    • If it is rdf:langString, then make a reference to the container_language in the #/$defs section
    • Create a string, boolean or numeric schema according to the datatype-to-schema mapping
  • If the property shape has an sh:nodeKind pointing to sh:IRI, generate a string schema of format iri-reference.
  • Otherwise, return an empty schema
• If the sh:minCount is > 0, the JSON key is added to the list of requiredProperties of the schema

Root node shape

With the provided root node shape IRI, create a reference to the corresponding schema from the #/$defs section.