每个用例都由一个椭圆形代表，用描述这个用例将要执行什么样的行为的说明型陈述进行标注。

Each use case is represented by an oval, and labeled with a declarative statement that describes what action the use case is intended to perform.

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根据Sulloway举出的其它研究，位于第一、中间和最后出生的人们的自尊心用图描述时也一样符合这U型曲线。

Sulloway cites other studies in which the self-esteem of first -, middle - and last-borns is plotted on a graph and follows the same curvilinear trajectory.

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