Nextcloud extension to WebDAV?

When I make a call to the WebDAV API, Nextcloud returns a few custom namespaces:

'xmlns:d': 'DAV:',
'xmlns:s': '',
'xmlns:cal': 'urn:ietf:params:xml:ns:caldav',
'xmlns:cs': '',
'xmlns:card': 'urn:ietf:params:xml:ns:carddav',
'xmlns:oc': '',
'xmlns:nc': ''

And I’m wondering is there any information about the custom properties or methods that Nextcloud provide (for example under oc: or nc: )?

The doc implies that Nextcloud simply supports the full WebDAV spec but I guess it does a bit more. For example the errors have custom info from SabreDAV.