Yes. Atom feed files are XML (eXtensible Markup Language) documents. Atom feed files must be well-formed XML documents, respecting the following XML rules.

► The first line must be the "xml" processing instruction with "version" and "encoding" attributes.

► There must be only one root element in a single XML document.

► All elements must be closed with the closing tags.

► One element can be nested inside another element.

► One element can not be partially nested inside another element.

► Element attribute values must be quoted with double quotes.

► Special characters in element attribute values or element contents must be protected using entities, like < and >.