declare namespace m = "http://www.milowski.com/Vocabulary/Math/Monos/2005/1/0"; declare namespace gap = "http://www.milowski.com/example"; declare function gap:convert-rational($v) as xs:double { if (contains($v,"/")) then number(substring-before($v,"/")) div number(substring-after($v,"/")) else number($v) }; (for $sol in /m:component-lp-list/m:component-lp/m:solution order by gap:convert-rational($sol/@value) descending return $sol)[1]/..