{
  "columns": [
    "invoiceDate$year",
    "invoiceDate$month",
    "invoiceAmount",
    "invoiceAmount__ytd"
  ],
  "groupBy": [
    "invoiceDate$year",
    "invoiceDate$month"
  ],
  "orderBy": [
    "invoiceDate$year",
    "invoiceDate$month"
  ],
  "timeWindow": {
    "field": "invoiceDate$id",
    "grain": "month",
    "comparison": "ytd",
    "range": "[)",
    "value": [
      "2012-10-01",
      "2012-12-01"
    ],
    "targetMetrics": [
      "invoiceAmount"
    ]
  },
  "limit": 500
}