This is a core mapping class, all objects representing GraphQL objects and fields are instance of that object. All instances of MUST be in the namespace prefix `gql: `. Example: query { planet { order_num } } will use `gql:planet` and `gql:order_num` to find RDF class and property. In RDF terms mappings should be defined as: `gql:planet gql:rdfClass ex:Planet` and `ex:planetOrder gql:field gql:order_num`.