{ "head": {
    "vars": [ "s" , "o" , "z" ]
  } ,
  "results": {
    "bindings": [
      { 
        "s": { "type": "uri" , "value": "http://example/a1" } ,
        "o": {
          "type": "triple" , 
          "value": {
            "subject":   { "type": "uri" , "value": "http://example/s" } ,
            "predicate": { "type": "uri" , "value": "http://example/p1" } ,
            "object":    { "type": "uri" , "value": "http://example/o" }
          }
        } ,
        "z": { "type": "uri" , "value": "http://example/a2" }
      }
    ]
  }
}