Consider extending the cardinality of role to "zero or more"? #1129
Description
The same person can play different roles in the making of a book; for instance with Media Overlays, the author can well be the narrator too.
<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
…
<dc:creator id="creator01">Herman Melville</dc:creator>
<meta refines="#creator01" property="role" scheme="marc:relators">aut</meta>
<meta refines="#creator01" property="role" scheme="marc:relators">nrt</meta>
…
</metadata>(I know, I know… but what if we find an old cylinder of Melville reading Moby Dick at the New York Society Library?)