The control events include install, update, start, and stop.
控制事件包括安装，更新，启动和停止。
2
A start node can only issue control flow, while stop and end nodes can also receive data flow.
开始节点只能发出控制流，而停止和结束节点还可以接收数据流。
3
There is a set of process engine APIs which you can use to control the process life cycle (for example, start, stop), and to handle work items for staff activity.