Check existence of duplicated items with XQuery - xquery

Question

I'm doing some exercises on XQuery and I can't figure out how to deal with this problem.
Let's say I have a FileSystem structured like this DTD: (Unspecified elements only contain PCData)
<!ELEMENT RootFolder ( File | Folder )* >
<!ELEMENT File ( Name, Type, Size, CreationDate, OwnerId )>
<!ELEMENT Folder ( Name, CreationDate (File | Folder)* ) >
How can I write a function that returns true/false checking whether the names of every resource (files and folders) are such that all of them have a distinct pathname?

Answer 1

Instead of checking for uniqueness, you could check for duplicates by checking to see if a Folder or File has a sibling with the same Name...
declare variable $in :=
<RootFolder>
<Folder>
<Name>user</Name>
<File>
<Name>Fred</Name>
</File>
<File>
<Name>Bill</Name>
</File>
<File>
<Name>Fred</Name>
</File>
</Folder>
<Folder>
<Name>manager</Name>
<File>
<Name>Jane</Name>
</File>
<File>
<Name>Mary</Name>
</File>
<File>
<Name>Jane</Name>
</File>
</Folder>
</RootFolder>;
declare function local:hasDupe($ctx as element()) as xs:boolean {
boolean($ctx//(File|Folder)[Name=following-sibling::*/Name])
};
local:hasDupe($in)
This would return true.

Answer 2

This query:
declare variable $in :=
<Folder Name="root">
<Folder Name="user">
<File Name="Fred"/>
<File Name="Bill"/>
<File Name="Fred"/>
</Folder>
<Folder Name="manager">
<File Name="Jane"/>
<File Name="Mary"/>
<File Name="Jane"/>
</Folder>
</Folder>;
declare function local:pathName($resource as element()) as xs:string {
string-join($resource/ancestor-or-self::*/#Name, '/')
};
for $resource in $in//(Folder | File)
let $path := local:pathName($resource)
group by $path
where count($resource) gt 1
return $path
returns
("root/manager/Jane", "root/user/Fred")
(in some undefined order)