{
  "host":"http://localhost:8080",
  "reset": true,
  "in":[
    {
      "id":"Tracker1",
      "type":"Tracker",
      "attributes":[
        { "name":"time", "type":"date" },
        { "name":"location", "type":"geo:point" }
      ]
    }
  ],
  "out":[
    {
      "id":"Fence1",
      "type":"Alert",
      "attributes":[
        { "name":"time", "type":"date" },
        { "name":"location", "type":"geo:point" },
        { "name":"inside", "type":"boolean" }
      ]
    }
  ],
  "statements":[
    "CREATE VARIABLE Geometry fence = polygon({point(0, 0), point(0,50), point(50,50), point(50, 0), point(0, 0)})",
    "CREATE WINDOW TrackerState.std:unique(id) as Alert",
    "INSERT INTO TrackerInside SELECT *, fence.contains(location) as inside FROM Tracker",
    "INSERT INTO FenceCross SELECT a.* FROM pattern [ every a=TrackerInside -> (timer:interval(4 sec) and not TrackerInside(id=a.id, inside!=a.inside)) ]",
    "ON FenceCross fc MERGE TrackerState ts WHERE fc.id = ts.id WHEN NOT MATCHED THEN INSERT SELECT id, time, location, inside WHEN MATCHED AND fc.inside != ts.inside THEN UPDATE SET inside = fc.inside",
    "INSERT INTO Alert SELECT * FROM TrackerState"
  ]
}