Message
ext-link that contains a DOI should have attribute @ext-link-type="doi"
Rule XPath:
This rule REPORTS an alert when the following is TRUE:
not(@ext-link-type = 'doi') and matches(concat(@xlink:href, ' ', string()), '(https?://(dx\.|www\.)?doi\.org|(https?://(dx\.|www\.)?doi\.org/|(doi)?:?\s*)?(10(\.[0-9]+)+/[^\s\?#]+)([#\?][^\s]+)?)',
'i') and not(matches(concat(@xlink:href, ' ', string()), 'https?://\S+/\S+(10(\.[0-9]+)+/[^\s\?#]+)',
'i'))