What is an XML (or XHTML) Serialisation?
The XML Serialization refers to the syntax defined by XML 1.0 and Namespaces in XML 1.0. A resource that has an XML MIME type, such as application/xhtml+xml or application/xml, is an XML document and if it uses elements in the HTML namespace, it contains XHTML. If the root element is “html” in the HTML namespace, the document is referred to as an XHTML document.