SCA不能够同时支持用于同一个交互作用点的被提供和被需求的接口，因此为提供和需求接口的服务端口分别创建导入和导出元素。

SCA cannot support both provided and required interfaces for the same interaction point, thus separate import and export elements are created for service ports that provide and require interfaces.

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首先被导出的元素是大的背景图。

The first element to be exported is the large background.

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向 BPEL 导出时，限制每个元素只能有一个输入标准。

Since you are exporting to BPEL, you are restricted to having only one input criterion per element.

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