{
  "nodes": [
    {
      "id": "n1",
      "type": "fileCity-system",
      "title": "抽城市",
      "config": { "filePath": "Data/cities.txt" }
    },
    {
      "id": "n2",
      "type": "weather-system",
      "title": "查天气"
    }
  ],
  "edges": [
    {
      "from": "n1",
      "to": "n2",
      "when": "hasValidCities"
    }
  ]
}