Today is Spring Festival, the first day of this year. I gone to the park with my parents. We have a dood time.
今天是春节，新年的第一天，我和爸爸妈妈去公园玩，我们玩的很开心。
This paper introduces the definition and denotation of classes in DOOD, then discusses the derived classes created by rules based on them.
文中给出了在DOOD中类的定义和表示，并以此为基础介绍了利用规则生成派生类。
This paper introduces the definition and denotation of classes in DOOD, then discusses the derived classes created by rules based on them.
文中给出了在DOOD中类的定义和表示，并以此为基础介绍了利用规则生成派生类。
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