(:
   file:    pop_distinct_institutions.xq
   date:    29-July-2010
   author:  Gary Lewis
   purpose: Combines institutions from pop_all_years.xml into an XML where each
            institution is listed only once.
   usage:   Run from path where program is located.
   example: zorba -f -q pop_distinct_institutions.xq -o pop_distinct_institutions.xml -z indent=yes
:)

<population>
{
for $unitid in distinct-values(fn:doc("pop_all_years.xml")/population/survey/inst/@unitid)
order by $unitid ascending
return <inst unitid="{$unitid}" />
}
</population>