Limiting the result to top four in xquery - xpath

Question

<a>
{
for $o in doc("x.xml")/users/org
where fn:count($o/mem)
order by fn:count($o/mem) descending
return <org>
<b> {$o/#name/string()} </b>
<c> {$o/#ab/string()} </c>
<d> {fn:count($o/mem)} </d>
</org>
}
</a>
I have ordered the results in an descending order but I just need top 4 result from this. I tried to use the sub-sequence method on the wiki page and also the [position() 1,4] method to find the top 4 but was not successful.

Answer 1

One possible way using two for loops and limit the inner for to return only the first 4 results :
<a>
{
for $p in
(
for $o in doc("x.xml")/users/org
where fn:count($o/mem)
order by fn:count($o/mem) descending
return <org>
<b> {$o/#name/string()} </b>
<c> {$o/#ab/string()} </c>
<d> {fn:count($o/mem)} </d>
</org>
)[position() <= 4]
return $p
}
</a>
update :
Turns out that we don't actually need the outer for :
<a>
{
(
for $o in doc("x.xml")/users/org
where fn:count($o/mem)
order by fn:count($o/mem) descending
return <org>
<b> {$o/#name/string()} </b>
<c> {$o/#ab/string()} </c>
<d> {fn:count($o/mem)} </d>
</org>
)[position() <= 4]
}
</a>