{
  "type": "object",
  "properties" : {
    "properties" : {
      "id": { "type": "integer" },
      "iid": { "type": "integer" },
      "project_id": { "type": "integer" },
      "title": { "type": "string" },
      "description": { "type": ["string", "null"] },
      "state": { "type": "string" },
      "created_at": { "type": "date" },
      "updated_at": { "type": "date" },
      "web_url": { "type": "uri" }
    },
    "required": [
      "id", "iid", "project_id", "title", "description",
      "state", "created_at", "updated_at", "web_url"
    ],
    "head_pipeline": {
      "oneOf": [
        { "type": "null" },
        { "$ref": "pipeline/detail.json" }
      ]
    }
  }
}