处理指令和注释也简化了标签名，这在XML中是无法实现的：前者用PI，后者用COMMENT。

Processing instructions and comments are also reduced to special tag names that are not available in XML: PI for the former, comment for the latter.

youdao

RFC在4.5和4.6节讨论内容结构，就何时使用处理指令和注释提供了非常合理的建议。

The RFC moves on to coverage of content constructs with sections 4.5 and 4.6, which offer very sensible advice on when to use processing instructions and comments.

youdao

节点可以包含文本、属性、其他节点(因此形成XML的层次结构)以及其他一些特殊的东西(比如处理指令和注释)。

A node can contain text, attributes, other nodes (hence, the hierarchical nature of XML), and a few other specialized things (such as processing instructions and comments).

youdao