I don't know for what this pebble is useful but it must be useful.

我不知道这块石头能用来干吗，但是它一定有用。

youdao

But for this data to be useful after a disk or server crash, it must be stored on another server.

但对于在磁盘或服务器崩溃后有用的数据，必须存储在另外一台服务器上。

youdao

Aesthetics matter, but first and foremost a language must be useful; it must allow real-world programmers to express real-world ideas succinctly and affordably.

漂亮也很重要，但是最重要的是有用。 一种编程语言必须让真实世界的程序员简洁并以较低代价表达真实世界的想法。

youdao

To win it, an invention must be original, useful and non-obvious.

ECONOMIST: Brains v bugs

The data must be archivable and searchable, making it useful for the long run, and allowing things like an idea repository available on-demand to people and systems throughout the business.

FORBES: Don't Erase The Master Plan: Digitally Capturing Big Ideas