@startuml
[*] --> notScheduled: initialize
notScheduled --> scheduling: setTimeout/\nXMLHttpRequest.send\nand so on

scheduling: zoneSpec.onScheduleTask
scheduling: zoneSpec.onHasTask

scheduling --> scheduled
scheduled --> running: timeout callback\nreadystatechange\ncallback
running: zoneSpec:onInvokeTask

scheduled --> canceling: clearTimeout\n/abort request
canceling: zoneSpec.onCancelTask
canceling --> notScheduled
canceling: zoneSpec.onHasTask
running --> notScheduled
running: zoneSpec.onHasTask
@enduml