如何用XQuery编写函数校验文件系统资源路径名是否唯一

Hey there! Let's work through this XQuery problem together. Since you didn't share the exact DTD structure, I'll go with standard assumptions for a filesystem XML setup that aligns with your note about unspecified elements containing PCData:

• Root element is <filesystem>
• Folders are <folder> elements with a name attribute, and can contain nested <folder> or <file> elements
• Files are <file> elements with a name attribute
• Any other elements just hold plain text, so we can ignore them for resource path checks

Here's a solution that creates a boolean-returning function to verify all resource paths are unique:

declare function local:all-paths-unique($fs as element(filesystem)) as xs:boolean {
    (: Collect every full path for files and folders :)
    let $all-resource-paths := local:get-full-resource-paths($fs, "")
    :(: If distinct paths count matches total count, all are unique :)
    return count(distinct-values($all-resource-paths)) eq count($all-resource-paths)
};

(: Helper function to recursively build full paths for all resources :)
declare function local:get-full-resource-paths($node as element(), $current-path as xs:string) as xs:string* {
    (: Process folders: add their path, then recurse into children :)
    if ($node instance of element(folder)) then
        let $folder-full-path := 
            if ($current-path eq "") then $node/@name 
            else concat($current-path, "/", $node/@name)
        return ($folder-full-path, local:get-full-resource-paths($node/*, $folder-full-path))
    (: Process files: return their full path :)
    else if ($node instance of element(file)) then
        concat($current-path, "/", $node/@name)
    (: Skip non-resource elements but recurse into their children just in case :)
    else
        local:get-full-resource-paths($node/*, $current-path)
};

How this works: #

1. Main function (local:all-paths-unique):

   • Calls the helper function to gather every full path from the filesystem.
   • Compares the number of distinct paths to the total number of paths. If they're equal, all paths are unique (returns true()); if not, there's a duplicate (returns false()).

2. Helper function (local:get-full-resource-paths):

   • Recursively traverses the XML structure:
     • For folders, it builds the full path by appending the folder's name to the current parent path, then returns that path plus all paths from the folder's children.
     • For files, it appends the file's name to the current path and returns that full path.
     • For any other elements (which hold PCData per your DTD), it skips the element itself but still checks its children (a safe fallback in case resources are nested unexpectedly).

Example usage: #

If your filesystem XML looks like this:

<filesystem>
    <folder name="projects">
        <file name="todo.md"/>
        <folder name="xquery-practice">
            <file name="path-check.xq"/>
        </folder>
    </folder>
    <folder name="downloads">
        <file name="archive.zip"/>
    </folder>
</filesystem>

Calling local:all-paths-unique(/filesystem) will return true(). But if you add a duplicate path (like another <file name="todo.md"/> directly under <filesystem>), the function will return false().

内容的提问来源于stack exchange，提问作者Hichame Yessou