按主系表分（my daily job主语,is系动词,cleaning the room表语）
cleaning动名词,解释或说明主语.当动名词或不定式作表语时,可以与主语互换位置,意思不变（谚语除外）
如：Cleaning the room is my daily job.
My idea is to start tomorrow.=To start tomorrow is my idea.