[FIG(quote)[
[FIGCAPTION[
[1] [CITE@en[Media RSS Specification]]
([TIME[2018-04-30 17:20:01 +09:00]])
<http://www.rssboard.org/media-rss#media-rating>
]FIGCAPTION]

> If this attribute is not included, the default scheme is urn:simple

]FIG]