{
  "type": "distinct",
  "input": {
    "type": "project",
    "input": {
      "type": "filter",
      "input": {
        "type": "minus",
        "input": [
          {
            "type": "minus",
            "input": [
              {
                "type": "bgp",
                "patterns": [
                  {
                    "type": "pattern",
                    "termType": "Quad",
                    "subject": {
                      "termType": "Variable",
                      "value": "s2"
                    },
                    "predicate": {
                      "termType": "NamedNode",
                      "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                    },
                    "object": {
                      "termType": "NamedNode",
                      "value": "http://example/Set"
                    },
                    "graph": {
                      "termType": "DefaultGraph",
                      "value": ""
                    }
                  },
                  {
                    "type": "pattern",
                    "termType": "Quad",
                    "subject": {
                      "termType": "Variable",
                      "value": "s1"
                    },
                    "predicate": {
                      "termType": "NamedNode",
                      "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                    },
                    "object": {
                      "termType": "NamedNode",
                      "value": "http://example/Set"
                    },
                    "graph": {
                      "termType": "DefaultGraph",
                      "value": ""
                    }
                  }
                ]
              },
              {
                "type": "filter",
                "input": {
                  "type": "bgp",
                  "patterns": [
                    {
                      "type": "pattern",
                      "termType": "Quad",
                      "subject": {
                        "termType": "Variable",
                        "value": "s1"
                      },
                      "predicate": {
                        "termType": "NamedNode",
                        "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                      },
                      "object": {
                        "termType": "NamedNode",
                        "value": "http://example/Set"
                      },
                      "graph": {
                        "termType": "DefaultGraph",
                        "value": ""
                      }
                    },
                    {
                      "type": "pattern",
                      "termType": "Quad",
                      "subject": {
                        "termType": "Variable",
                        "value": "s2"
                      },
                      "predicate": {
                        "termType": "NamedNode",
                        "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                      },
                      "object": {
                        "termType": "NamedNode",
                        "value": "http://example/Set"
                      },
                      "graph": {
                        "termType": "DefaultGraph",
                        "value": ""
                      }
                    },
                    {
                      "type": "pattern",
                      "termType": "Quad",
                      "subject": {
                        "termType": "Variable",
                        "value": "s1"
                      },
                      "predicate": {
                        "termType": "NamedNode",
                        "value": "http://example/member"
                      },
                      "object": {
                        "termType": "Variable",
                        "value": "x"
                      },
                      "graph": {
                        "termType": "DefaultGraph",
                        "value": ""
                      }
                    }
                  ]
                },
                "expression": {
                  "type": "expression",
                  "subType": "existence",
                  "not": true,
                  "input": {
                    "type": "bgp",
                    "patterns": [
                      {
                        "type": "pattern",
                        "termType": "Quad",
                        "subject": {
                          "termType": "Variable",
                          "value": "s2"
                        },
                        "predicate": {
                          "termType": "NamedNode",
                          "value": "http://example/member"
                        },
                        "object": {
                          "termType": "Variable",
                          "value": "x"
                        },
                        "graph": {
                          "termType": "DefaultGraph",
                          "value": ""
                        }
                      }
                    ]
                  }
                }
              }
            ]
          },
          {
            "type": "filter",
            "input": {
              "type": "bgp",
              "patterns": [
                {
                  "type": "pattern",
                  "termType": "Quad",
                  "subject": {
                    "termType": "Variable",
                    "value": "s1"
                  },
                  "predicate": {
                    "termType": "NamedNode",
                    "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                  },
                  "object": {
                    "termType": "NamedNode",
                    "value": "http://example/Set"
                  },
                  "graph": {
                    "termType": "DefaultGraph",
                    "value": ""
                  }
                },
                {
                  "type": "pattern",
                  "termType": "Quad",
                  "subject": {
                    "termType": "Variable",
                    "value": "s2"
                  },
                  "predicate": {
                    "termType": "NamedNode",
                    "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"
                  },
                  "object": {
                    "termType": "NamedNode",
                    "value": "http://example/Set"
                  },
                  "graph": {
                    "termType": "DefaultGraph",
                    "value": ""
                  }
                },
                {
                  "type": "pattern",
                  "termType": "Quad",
                  "subject": {
                    "termType": "Variable",
                    "value": "s2"
                  },
                  "predicate": {
                    "termType": "NamedNode",
                    "value": "http://example/member"
                  },
                  "object": {
                    "termType": "Variable",
                    "value": "x"
                  },
                  "graph": {
                    "termType": "DefaultGraph",
                    "value": ""
                  }
                }
              ]
            },
            "expression": {
              "type": "expression",
              "subType": "existence",
              "not": true,
              "input": {
                "type": "bgp",
                "patterns": [
                  {
                    "type": "pattern",
                    "termType": "Quad",
                    "subject": {
                      "termType": "Variable",
                      "value": "s1"
                    },
                    "predicate": {
                      "termType": "NamedNode",
                      "value": "http://example/member"
                    },
                    "object": {
                      "termType": "Variable",
                      "value": "x"
                    },
                    "graph": {
                      "termType": "DefaultGraph",
                      "value": ""
                    }
                  }
                ]
              }
            }
          }
        ]
      },
      "expression": {
        "type": "expression",
        "subType": "operator",
        "operator": "<",
        "args": [
          {
            "type": "expression",
            "subType": "operator",
            "operator": "str",
            "args": [
              {
                "type": "expression",
                "subType": "term",
                "term": {
                  "termType": "Variable",
                  "value": "s1"
                }
              }
            ]
          },
          {
            "type": "expression",
            "subType": "operator",
            "operator": "str",
            "args": [
              {
                "type": "expression",
                "subType": "term",
                "term": {
                  "termType": "Variable",
                  "value": "s2"
                }
              }
            ]
          }
        ]
      }
    },
    "variables": [
      {
        "termType": "Variable",
        "value": "s1"
      },
      {
        "termType": "Variable",
        "value": "s2"
      }
    ]
  }
}