关系模型基于谓词逻辑和集合论。

It seems to me that the natural world is the greatest source of excitement; the greatest source of visual beauty; the greatest source of intellectual interest. It is the greatest source of so much in life that makes life worth living.

每部电影都是一段旅程，作为导演，你必须为意外做好准备。

设计中最难的部分是保持功能的简洁。