{
  "type": "project",
  "input": {
    "type": "filter",
    "input": {
      "type": "bgp",
      "patterns": [
        {
          "type": "pattern",
          "termType": "Quad",
          "subject": {
            "termType": "Variable",
            "value": "a"
          },
          "predicate": {
            "termType": "NamedNode",
            "value": "https://mydom2#predB"
          },
          "object": {
            "termType": "Variable",
            "value": "b"
          },
          "graph": {
            "termType": "DefaultGraph",
            "value": ""
          }
        }
      ]
    },
    "expression": {
      "type": "expression",
      "subType": "existence",
      "not": false,
      "input": {
        "type": "join",
        "input": [
          {
            "type": "bgp",
            "patterns": [
              {
                "type": "pattern",
                "termType": "Quad",
                "subject": {
                  "termType": "Variable",
                  "value": "var0"
                },
                "predicate": {
                  "termType": "NamedNode",
                  "value": "https://mydom2#predN"
                },
                "object": {
                  "termType": "Variable",
                  "value": "q"
                },
                "graph": {
                  "termType": "DefaultGraph",
                  "value": ""
                }
              }
            ]
          },
          {
            "type": "project",
            "input": {
              "type": "extend",
              "input": {
                "type": "extend",
                "input": {
                  "type": "bgp",
                  "patterns": [
                    {
                      "type": "pattern",
                      "termType": "Quad",
                      "subject": {
                        "termType": "Variable",
                        "value": "_s"
                      },
                      "predicate": {
                        "termType": "Variable",
                        "value": "p"
                      },
                      "object": {
                        "termType": "Variable",
                        "value": "_o"
                      },
                      "graph": {
                        "termType": "DefaultGraph",
                        "value": ""
                      }
                    }
                  ]
                },
                "variable": {
                  "termType": "Variable",
                  "value": "q2"
                },
                "expression": {
                  "type": "expression",
                  "subType": "term",
                  "term": {
                    "termType": "Variable",
                    "value": "_s"
                  }
                }
              },
              "variable": {
                "termType": "Variable",
                "value": "var0"
              },
              "expression": {
                "type": "expression",
                "subType": "term",
                "term": {
                  "termType": "Variable",
                  "value": "_o"
                }
              }
            },
            "variables": [
              {
                "termType": "Variable",
                "value": "q2"
              },
              {
                "termType": "Variable",
                "value": "var0"
              }
            ]
          }
        ]
      }
    }
  },
  "variables": [
    {
      "termType": "Variable",
      "value": "s"
    },
    {
      "termType": "Variable",
      "value": "p"
    },
    {
      "termType": "Variable",
      "value": "o"
    }
  ]
}
