首先定义尺素和尺素链等概念，并在此基础上建立尺寸公差的尺素表示模型及其语义映射；

Firstly, the concepts of dimensional element (DE) and dimensional element-chain (DEC) are defined, and a geometric tolerancing model expressed by DE and its semantic mapping are also given.

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在第二章中，我们讨论紧致度量空间上连续自映射的可链点集的性质，特别是链回归点的可链点集的性质。

In Chapter Two, we discuss properties of the set of chainable points of a continuous self-map fon an impact metric space, especially those of chain recurrent points.

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