The XSL output method determines the default MIME type, and also some aspects of syntax in serialized tags:
An explicit
<xsl:output method="..."/>
in the stylesheetOtherwise, the default is HTML
The XML declaration is written by default, for output method XML. This is appropriate for a complete XML document written from a single transform. If the XML output is written as a series of nested fragments, then the XML declaration must be disabled for the embedded output using an extra flag on the <xsl:output>
element. For example:
<xsl:output method="xml" omit
xml
declaration="yes"/>