declare function local:overlap($manager, $tstart,$tend) {

if (xs:date($manager/@tstart) <= xs:date($tstart) and
      xs:date($manager/@tend) >= xs:date($tend))
  then (
     element mgrno {
	attribute tstart{$tstart},
	attribute tend{$tend},
	$manager/text()
     })

else if (xs:date($manager/@tstart) <= xs:date($tstart) and
      (xs:date($manager/@tend)) >= xs:date($tstart) and
      (xs:date($manager/@tend)) <= xs:date($tend))
  then (
     element mgrno {
	attribute tstart{$tstart},
	attribute tend{$manager/@tend},
	$manager/text()
     })
     
 else if (($manager/xs:date(@tend) >= xs:date($tend)) and
      ($manager/xs:date(@tstart) >= xs:date($tstart)) and
      ($manager/xs:date(@tstart) <= xs:date($tend)))
  then (
     element mgrno {
	attribute tstart{$manager/@tstart},
	attribute tend{$tend},
	$manager/text()
     }
  )
  else if (($manager/xs:date(@tstart) >= xs:date($tstart)) and
      ($manager/xs:date(@tend) <= xs:date($tend)))
  then (
    element mgrno {
	attribute tstart{$manager/@tstart},
	attribute tend{$manager/@tend},
	$manager/text()
     }
  )
     else ()
};
declare function local:get_all(){
for $r in doc("v-depts.xml")/departments/department
let $k := for $m in $r/mgrno return local:overlap($m, '1994-05-06', '9995-05-06')
where exists($k)
return element event{$r/deptno, $k}  
};

let $data := local:get_all()
return $data