{
  "type": "project",
  "input": {
    "type": "extend",
    "input": {
      "type": "group",
      "input": {
        "type": "extend",
        "input": {
          "type": "leftjoin",
          "input": [
            {
              "type": "bgp",
              "patterns": [
                {
                  "type": "pattern",
                  "termType": "Quad",
                  "subject": {
                    "termType": "Variable",
                    "value": "s"
                  },
                  "predicate": {
                    "termType": "NamedNode",
                    "value": "http://example/p"
                  },
                  "object": {
                    "termType": "Variable",
                    "value": "v"
                  },
                  "graph": {
                    "termType": "DefaultGraph",
                    "value": ""
                  }
                }
              ]
            },
            {
              "type": "bgp",
              "patterns": [
                {
                  "type": "pattern",
                  "termType": "Quad",
                  "subject": {
                    "termType": "Variable",
                    "value": "s"
                  },
                  "predicate": {
                    "termType": "NamedNode",
                    "value": "http://example/q"
                  },
                  "object": {
                    "termType": "Variable",
                    "value": "w"
                  },
                  "graph": {
                    "termType": "DefaultGraph",
                    "value": ""
                  }
                }
              ]
            }
          ]
        },
        "variable": {
          "termType": "Variable",
          "value": "X"
        },
        "expression": {
          "type": "expression",
          "subType": "operator",
          "operator": "coalesce",
          "args": [
            {
              "type": "expression",
              "subType": "term",
              "term": {
                "termType": "Variable",
                "value": "w"
              }
            },
            {
              "type": "expression",
              "subType": "term",
              "term": {
                "termType": "Literal",
                "value": "1605-11-05",
                "datatype": {
                  "termType": "NamedNode",
                  "value": "http://www.w3.org/2001/XMLSchema#date"
                }
              }
            }
          ]
        }
      },
      "variables": [
        {
          "termType": "Variable",
          "value": "X"
        }
      ],
      "aggregates": [
        {
          "type": "expression",
          "subType": "aggregate",
          "aggregator": "sample",
          "expression": {
            "type": "expression",
            "subType": "term",
            "term": {
              "termType": "Variable",
              "value": "v"
            }
          },
          "distinct": false,
          "variable": {
            "termType": "Variable",
            "value": "var0"
          }
        }
      ]
    },
    "variable": {
      "termType": "Variable",
      "value": "S"
    },
    "expression": {
      "type": "expression",
      "subType": "term",
      "term": {
        "termType": "Variable",
        "value": "var0"
      }
    }
  },
  "variables": [
    {
      "termType": "Variable",
      "value": "X"
    },
    {
      "termType": "Variable",
      "value": "S"
    }
  ]
}