f:Extension/f:value[x] 1 low: minimum cardinality of 'low' is 1 high: minimum cardinality of 'high' is 1 f:Extension/f:value[x]/f:low 1 comparator: maximum cardinality of 'comparator' is 0 f:Extension/f:value[x]/f:high 1 comparator: maximum cardinality of 'comparator' is 0