Sequence Diagram

Diagram Model saved in JSON format:

{ "class": "go.GraphLinksModel",
  "nodeDataArray": [
{"key":"Fred", "text":"Fred: Patron", "isGroup":true, "loc":"0 0", "duration":9},
{"key":"Bob", "text":"Bob: Waiter", "isGroup":true, "loc":"100 0", "duration":9},
{"key":"Hank", "text":"Hank: Cook", "isGroup":true, "loc":"200 0", "duration":9},
{"key":"Renee", "text":"Renee: Cashier", "isGroup":true, "loc":"300 0", "duration":9},
{"group":"Bob", "start":1, "duration":2},
{"group":"Hank", "start":2, "duration":3},
{"group":"Fred", "start":3, "duration":1},
{"group":"Bob", "start":5, "duration":1},
{"group":"Fred", "start":6, "duration":2},
{"group":"Renee", "start":8, "duration":1}
 ],
  "linkDataArray": [
{"from":"Fred", "to":"Bob", "text":"order", "time":1},
{"from":"Bob", "to":"Hank", "text":"order food", "time":2},
{"from":"Bob", "to":"Fred", "text":"serve drinks", "time":3},
{"from":"Hank", "to":"Bob", "text":"finish cooking", "time":5},
{"from":"Bob", "to":"Fred", "text":"serve food", "time":6},
{"from":"Fred", "to":"Renee", "text":"pay", "time":8}
 ]}