{ "head": {
    "vars": [ "s" , "o" , "z" ]
  } ,
  "results": {
    "bindings": [
      { 
        "s": { "type": "uri" , "value": "http://example/a1" } ,
        "o": { "type": "uri" , "value": "http://example/reifier" } ,
        "z": { "type": "uri" , "value": "http://example/a2" }
      }
    ]
  }
}
