--如何解析这段代码中所有的信息呢？自己试了一下openxml感觉并列分支太多，不知道怎么分？如果用xquery呢？
就是要提取每个节点下的内容，像country，date等等这些值（像country这些有重复，这时就要附加节点属性来区分，比如附加num。。其他雷同）

<?xml version="1.0" encoding="UTF-8"?>
<us-bibliographic-data-grant>
<classification-national>
<country>US</country>
</classification-national>
<invention-title id="d2e53">Undergarment</invention-title>
<references-cited>
<citation>
<patcit num="00001">
<document-id>
<country>US</country>
<date>19130233</date>
</document-id>
</patcit>
<classification-national><country>US</country><main-classification>602 67</main-classification></classification-national>
</citation>
<citation>
<patcit num="00002">
<document-id>
<country>US</country>
<date>19200599</date>
</document-id>
</patcit>
<classification-national><country>US</country><main-classification>602 67</main-classification></classification-national>
</citation>
</references-cited>
</us-bibliographic-data-grant>