Each LU has a root element, which is the top-most Package.

每一个LU(逻辑单元)都具有一个根结点元素，亦即最顶部的包。

youdao

Each LU has a root element, which is the top-most Package.

每一个LU(逻辑单元)都具有一个根结点元素，亦即最顶部的包。

youdao