why EventNodeDataChanged trigger children watch?

[darkterrorooo]

as source code below, if data of path change , it will trigger three event.
why not only trigger watchTypeData

func (c *Conn) recvLoop(conn net.Conn) error {
....
case EventNodeDeleted, EventNodeDataChanged:
wTypes = append(wTypes, watchTypeExist, watchTypeData, watchTypeChild)

....
}