{
  "type": "project",
  "input": {
    "type": "join",
    "input": [
      {
        "type": "values",
        "variables": [
          {
            "termType": "Variable",
            "value": "book"
          }
        ],
        "bindings": [
          {
            "book": {
              "termType": "NamedNode",
              "value": "http://example.org/book/book1"
            }
          }
        ]
      },
      {
        "type": "bgp",
        "patterns": [
          {
            "type": "pattern",
            "termType": "Quad",
            "subject": {
              "termType": "Variable",
              "value": "book"
            },
            "predicate": {
              "termType": "NamedNode",
              "value": "http://purl.org/dc/elements/1.1/title"
            },
            "object": {
              "termType": "Variable",
              "value": "title"
            },
            "graph": {
              "termType": "DefaultGraph",
              "value": ""
            }
          },
          {
            "type": "pattern",
            "termType": "Quad",
            "subject": {
              "termType": "Variable",
              "value": "book"
            },
            "predicate": {
              "termType": "NamedNode",
              "value": "http://example.org/ns#price"
            },
            "object": {
              "termType": "Variable",
              "value": "price"
            },
            "graph": {
              "termType": "DefaultGraph",
              "value": ""
            }
          }
        ]
      }
    ]
  },
  "variables": [
    {
      "termType": "Variable",
      "value": "book"
    },
    {
      "termType": "Variable",
      "value": "title"
    },
    {
      "termType": "Variable",
      "value": "price"
    }
  ]
}