在DDD中定义多对多关系

Are many-to-many table structures defined as Value Objects in DDD? What if my many-to-many structure has a unique id? Also, what about 1-to-many relationships? For instance, if i have 2 structures Post & Comment with 1-to-many (respectively) wouldn't Comment be a Value Object since it technically cannot exist without a corresponding Post? But what if it has a unique Id (Comment_Id)? That makes it identifiable and therefore a non-value object entity? So, which is it?Are many-to-many table structures defined as Va