图2：软件开发生命周期的螺旋模型

Figure 2: Spiral model of the software development lifecycle

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图1：软件开发生命周期的瀑布模型。

Figure 1: Waterfall software development lifecycle.

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图1：软件开发生命周期的瀑布模型。

Figure 1: Waterfall software development lifecycle.

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