Open Assembly diagram, and add Echo for both interface and reference.

打开组装关系图，同时为接口和引用添加echo。

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To this, add a sequence activity that will be the outermost structural element required in the Echo process.

为此，请添加一个sequence活动，它将成为回送流程所要求的最外层的结构元素。

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For the echo process, you need some steps to be taken in a certain sequence, so you add a sequence as the top-level activity activity and then populate it with a receive and reply later.

对于这个回送流程，您需要让有些步骤按照一定的顺序执行，所以，您添加一个sequence作为顶层活动，然后再将receive和reply植入sequence。

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