{
  "name": "Computed action values",
  "rules": [
    {
      "id": "percentage-discount",
      "description": "An output value can be an expression over fact fields, not just a constant.",
      "condition": { "field": "Customer.IsVip", "operator": "Equals", "value": true },
      "actions": [
        {
          "type": "setOutput",
          "target": "DiscountAmount",
          "value": { "op": "multiply", "operands": [ { "field": "Order.Total" }, 0.1 ] }
        },
        {
          "type": "setOutput",
          "target": "Message",
          "value": { "op": "concat", "operands": [ "Thanks ", { "field": "Customer.Name" }, ", you saved 10%!" ] }
        }
      ]
    },
    {
      "id": "net-total",
      "description": "Expressions nest; coalesce guards a possibly-missing discount field.",
      "condition": { "field": "Order.Total", "operator": "GreaterThan", "value": 0 },
      "actions": [
        {
          "type": "setOutput",
          "target": "NetTotal",
          "value": {
            "op": "subtract",
            "operands": [
              { "field": "Order.Total" },
              { "op": "coalesce", "operands": [ { "field": "Order.DiscountApplied" }, 0 ] }
            ]
          }
        }
      ]
    }
  ]
}