Type extensions, which enable you to extend an existing type easily without the additional overhead work of creating a new derived type.

型别扩充，可让您轻松扩充现有型别，而不需要额外建立新的衍生型别。

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When you add a lifeline to an interaction (sequence diagram), its type is stored in the root model, unless you have created the lifeline from an existing type.

除非您是基于现有类型创建了生命线，否则向交互（序列图）添加生命线时，其类型将存储在根模型中。

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When you add a lifeline to an interaction (sequence diagram), its type is stored in the root model, unless you have created the lifeline from an existing type.

除非您是基于现有类型创建了生命线，否则向交互（序列图）添加生命线时，其类型将存储在根模型中。

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