这是因为回退机制只能用于指令元素而不能用于声明。

That is because the fallback mechanism only works for instruction elements, not declarations.

youdao

在两个版本的XSLT中第2层的元素都称为指令。

The elements at level 2 are called instructions in both versions of XSLT.

youdao

关于XSLT中的“指令”和“声明”元素请参阅结构表和后面的说明。

See the structure table and the following remarks for details about "instruction" and "declaration" elements in XSLT.

youdao