The <xsl:namespace-alias> element is a rarely used device that maps a namespace in the stylesheet to a different namespace in the output tree. The most common use for this element is in generating a stylesheet from another stylesheet. To prevent a normally xsl:-prefixed literal result element (which should be copied as-is to the result tree) from being misunderstood by the processor, it is assigned a temporary namespace which is appropriately re-converted back to the XSLT namespace in the output tree.