{
  "type": "project",
  "input": {
    "type": "filter",
    "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": ""
          }
        }
      ]
    },
    "expression": {
      "type": "expression",
      "subType": "operator",
      "operator": "regex",
      "args": [
        {
          "type": "expression",
          "subType": "term",
          "term": {
            "termType": "Variable",
            "value": "o"
          }
        },
        {
          "type": "expression",
          "subType": "term",
          "term": {
            "termType": "Literal",
            "value": "foo",
            "language": "en",
            "datatype": {
              "termType": "NamedNode",
              "value": "http://www.w3.org/1999/02/22-rdf-syntax-ns#langString"
            }
          }
        },
        {
          "type": "expression",
          "subType": "term",
          "term": {
            "termType": "Literal",
            "value": "i",
            "datatype": {
              "termType": "NamedNode",
              "value": "http://www.w3.org/2001/XMLSchema#string"
            }
          }
        }
      ]
    }
  },
  "variables": [
    {
      "termType": "Variable",
      "value": "o"
    },
    {
      "termType": "Variable",
      "value": "p"
    },
    {
      "termType": "Variable",
      "value": "s"
    }
  ]
}