Return a nested data structure from a SPARQL query

Question

If I have a graph with this kind of structure:

@prefix  :        .
@prefix  rdf:     .
         


        

Answer 1

You could use a CONSTRUCT query with JSON-LD Framing.

Example query (on DBpedia endpoint)

CONSTRUCT
{
  ?person  rdf:type       foaf:Person ;
           dbo:birthName  ?name1s ;
           dbo:birthDate  ?date1s ;
           dbo:spouse     ?spouse .
  ?spouse  rdf:type       foaf:Person ; 
           dbo:birthName  ?name2s ;
           dbo:birthDate  ?date2s .
}
WHERE
{
  ?person  dbo:birthName  ?name1 ;
           dbo:birthDate  ?date1 ;
           dbo:spouse     ?spouse .
  ?spouse  dbo:birthName  ?name2 ;
           dbo:birthDate  ?date2 .
  BIND (str(?name1) AS ?name1s)
  BIND (str(?date1) AS ?date1s)
  BIND (str(?name2) AS ?name2s)
  BIND (str(?date2) AS ?date2s)
  VALUES (?person) { ( dbr:Brad_Pitt ) }
}

Output (in JSON-LD format with context)

{ "@context": {
    "spouse": { "@id": "http://dbpedia.org/ontology/spouse"},
    "birthDate": { "@id": "http://dbpedia.org/ontology/birthDate" },
    "birthName": { "@id": "http://dbpedia.org/ontology/birthName" } },
  "@graph": [
    { "@id": "http://dbpedia.org/resource/Angelina_Jolie",
      "birthName": "Angelina Jolie Voight",
      "birthDate": "1975-06-04" },
    { "@id": "http://dbpedia.org/resource/Brad_Pitt",
      "@type": "http://xmlns.com/foaf/0.1/Person",
      "birthName": "William Bradley Pitt",
      "spouse": [ "http://dbpedia.org/resource/Angelina_Jolie",
                  "http://dbpedia.org/resource/Jennifer_Aniston" ],
      "birthDate": "1963-12-18" },
    { "@id": "http://dbpedia.org/resource/Jennifer_Aniston",
      "birthName": "Jennifer Joanna Aniston",
      "birthDate": "1969-02-11" }
] }

JSON-LD Frame (very simple)

{
  "@context": {"dbo": "http://dbpedia.org/ontology/",
               "dbr": "http://dbpedia.org/resource/",
               "foaf": "http://xmlns.com/foaf/0.1/"},
  "dbo:spouse": {
   }
}

Framed JSON-LD (playground)

{
  "@context": {
    "dbo": "http://dbpedia.org/ontology/",
    "dbr": "http://dbpedia.org/resource/",
    "foaf": "http://xmlns.com/foaf/0.1/"
  },
  "@graph": [
    {
      "@id": "dbr:Brad_Pitt",
      "@type": "foaf:Person",
      "dbo:birthDate": "1963-12-18",
      "dbo:birthName": "William Bradley Pitt",
      "dbo:spouse": [
        {
          "@id": "dbr:Angelina_Jolie",
          "@type": "foaf:Person",
          "dbo:birthDate": "1975-06-04",
          "dbo:birthName": "Angelina Jolie Voight"
        },
        {
          "@id": "dbr:Jennifer_Aniston",
          "@type": "foaf:Person",
          "dbo:birthDate": "1969-02-11",
          "dbo:birthName": "Jennifer Joanna Aniston"
        }
      ]
    }
  ]
}

Some discussion

JSON-LD Framing is an unofficial, yet well implemented specification that describes a deterministic layout for serializing an RDF graph into a particular JSON-LD document layout.

Obviously, with blank nodes property lists, one can achieve something structurally similar to the output you want:

Brad_Pitt
        dbo:birthName   "William Bradley Pitt" ;
        dbo:birthDate   "1963-12-18" .
        dbo:spouse  [   dbo:birthName   "Angelina Jolie Voight" ;
                        dbo:birthDate   "1975-06-04" ] ,
                    [   dbo:birthName   "Jennifer Joanna Aniston" ;
                        dbo:birthDate   "1969-02-11" ] .

However, this is Turtle, not JSON, and nobody can garantee that these blank nodes property lists will be used in serialization.