yes, exactly, not sure why your comment was downvoted. Also, generally it's not cardinality of 0..1, it is `[]` vs `xs:[]`, that is - either empty, or a multitu

yes, exactly, not sure why your comment was downvoted. Also, generally it's not cardinality of 0..1, it is `[]` vs `xs:[]`, that is - either empty, or a multitude of values, where 1 is a specific instance of the multitude (singleton).