"The best ideas come when you're not trying too hard."

关系模型基于谓词逻辑和集合论，为数据库管理提供了坚实的数学基础。

The voice is an instrument that never stops evolving.

You are too generous to trifle with me. If your feelings are still what they were last April, tell me so at once. My affections and wishes are unchanged, but one word from you will silence me on this subject forever.