xpath - XQuery：如何将字符串转换为 XPath 规则

Question

下面是一个简单的 XQuery，它将针对 htm 文件运行 xpath 并返回找到了多少匹配的标签。xpath 规则在变量 $rule 中，但我想改用字符串变量 $rule-unused。如何将此字符串转换为节点集并让它在我的文档中运行，类似于 $document//$rule ？

    xquery version "3.1";

    declare namespace persons="http://www.test.com/test/profiles";
    declare variable $uri as xs:string := "/db/apps/Persons/profile.htm";
    declare variable $rule-unused as xs:string := "//persons:relationship";

    let $document := doc($uri)
    let $rule := //persons:relationship
    let $all-lines := $document//$rule
    return
    <test>
        {
            count( $all-lines )
        }
    </test>

标签： xpathxquery