f:Condition category: maximum cardinality of 'category' is 1 f:Condition/f:subject id: maximum cardinality of 'id' is 1 reference: maximum cardinality of 'reference' is 1 type: maximum cardinality of 'type' is 1 identifier: maximum cardinality of 'identifier' is 1 display: maximum cardinality of 'display' is 1