MTBF quite commonly appears as a non-functional requirement.

MTBF 通常作为非功能需求出现。

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These non-functional requirements provide guidance on proper usage.

这些非功能需求提供了恰当使用的指南。

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Non-functional requirements describe the attributes of the portal system.

非实用需求描述门户系统的属性。

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Yesterday, they took down Sony and Playstaion.com, and the Playstation Network was non-functional most of the day.

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Somehow, our unit got into an endless loop of trying to install a software upgrade and basically became non-functional.

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Unfortunately, we were given a non-functional dummy unit to play with so we can't comment on things like screen quality or subjective performance.

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