{
  "type": "from",
  "input": {
    "type": "project",
    "input": {
      "type": "join",
      "input": [
        {
          "type": "graph",
          "input": {
            "type": "bgp",
            "patterns": [
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "alice"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/mbox"
                },
                "object": {
                  "termType": "NamedNode",
                  "value": "mailto:alice@work.example"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              },
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "alice"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/knows"
                },
                "object": {
                  "termType": "Variable",
                  "value": "whom"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              },
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "whom"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/mbox"
                },
                "object": {
                  "termType": "Variable",
                  "value": "mbox"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              },
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "whom"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://www.w3.org/2000/01/rdf-schema#seeAlso"
                },
                "object": {
                  "termType": "Variable",
                  "value": "ppd"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              },
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "ppd"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                },
                "object": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/PersonalProfileDocument"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              }
            ]
          },
          "name": {
            "termType": "NamedNode",
            "value": "http://example.org/foaf/aliceFoaf"
          }
        },
        {
          "type": "graph",
          "input": {
            "type": "bgp",
            "patterns": [
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
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                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/mbox"
                },
                "object": {
                  "termType": "Variable",
                  "value": "mbox"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
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                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "w"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "http://xmlns.com/foaf/0.1/nick"
                },
                "object": {
                  "termType": "Variable",
                  "value": "nick"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              }
            ]
          },
          "name": {
            "termType": "Variable",
            "value": "ppd"
          }
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    "variables": [
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        "termType": "Variable",
        "value": "mbox"
      },
      {
        "termType": "Variable",
        "value": "nick"
      },
      {
        "termType": "Variable",
        "value": "ppd"
      }
    ]
  },
  "default": [],
  "named": [
    {
      "termType": "NamedNode",
      "value": "http://example.org/foaf/aliceFoaf"
    },
    {
      "termType": "NamedNode",
      "value": "http://example.org/foaf/bobFoaf"
    }
  ]
}