其结构是固定的，意思上的主语并不是句子的主语。
generally speaking 一般说来
talking of (speaking of) 说道
strictly speaking 严格的说
judging from 从…判断
all things considered 从整体来看
taking all things into consideration 全面看来
Judging from his face, he must be ill. 从他的脸色看，他一定是病了。
Generally speaking, dogs can run faster than pigs. 总的来说，狗比猪跑得快。 (speaking 并不是dogs 的动作)