f:RequestGroup/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 f:RequestGroup/f:action resource: minimum cardinality of 'resource' is 1