Notification can also be used to trigger events , such as reacting to a state change that surpasses a given threshold , as in the case of dwindling resources like memory or disk space 通知还可以用于触发事件，如对于超过设置阀值（比如内存或者磁盘空间等资源不足）的状态改变做出反应。
Stores logging events in an internal cyclic buffer and sends them as an instant message only when the logging request received triggers a user - specified condition . optionally , users may provide a triggering event evaluator class 把日志记录事件存储在一个内部循环缓冲区（ cyclic buffer ）中，并且仅当所接收到的日志记录请求触发了某个用户指定的条件时，才把这些事件作为即时消息来发送。
