Collection restricted to single value, case complex field, the UI is that one of a single field. See how in JSON instance is still a collection / JSON array Required [element], Collection with one item, with Complex Type [Sub] localName is [Hello] without namespace Required [element], Single Occurrence, with Simple Type [inline-Form-HelloSingle] localName is [HelloSingle] without namespace Collection restricted to single value, case complex field, the UI is that one of a single field. See how in JSON instance is still a collection / JSON array Required [element], Single Occurrence, with Simple Type [inline-Sub-Sub1] localName is [Sub1] without namespace Required [element], Single Occurrence, with Simple Type [inline-Sub-Sub2] localName is [Sub2] without namespace