#data
<item xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://purl.org/rss/1.0/" rdf:about="http://a/"
    xmlns:content="http://purl.org/rss/1.0/modules/content/">
  <content:items/>
</item>
#errors
/item;child element missing;link;m
/item;child element missing;title;m
/item/items;element not allowed;m
/item/items;element not defined;m

#data
<content:item
    xmlns:content="http://purl.org/rss/1.0/modules/content/">
</content:item>
#errors
/item;element not defined;m

#data
<content:format
    xmlns:content="http://purl.org/rss/1.0/modules/content/">
</content:format>
#errors
/format;element not defined;m