f:DocumentReference type: minimum cardinality of 'type' is 1 subject: minimum cardinality of 'subject' is 1 f:DocumentReference/f:type id: maximum cardinality of 'id' is 1 text: maximum cardinality of 'text' is 1 f:DocumentReference/f:content/f:attachment id: maximum cardinality of 'id' is 1 contentType: minimum cardinality of 'contentType' is 1 contentType: maximum cardinality of 'contentType' is 1 language: maximum cardinality of 'language' is 1 data: maximum cardinality of 'data' is 1 url: maximum cardinality of 'url' is 1 size: maximum cardinality of 'size' is 1 hash: maximum cardinality of 'hash' is 1 title: maximum cardinality of 'title' is 1 creation: maximum cardinality of 'creation' is 1