First, you create a document library that stores the advanced search attributes and optional values.

首先，创建一个存储高级搜索属性和可选值的文档库。

youdao

The basic library is optional; anybody can create an alternative framework.

这个基本类库是可选的；任何人都可以创建框架来替换它。

youdao

The real power of XProc is embodied in its standard library of required and optional steps, which perform a wide variety of tasks, such as.

Xproc真正的强大之处在于必需和可选步骤的标准库，这些步骤执行广泛的任务，例如。

youdao

So the library books are all optional background.

所以图书馆内的书,都是可供选择的背景资料

耶鲁公开课 - 金融市场课程节选

This truly portable library can carry up to 1000 titles - and now even 8000 titles more with an optional microSD card.

ENGADGET: Bookeen's upgraded, colorful Cybook Opus to debut on May 7