The xsl:fallback element is used to define recovery action to be taken when an instruction
element is used in the stylesheet and no implementation of that element is available. An element is an
instruction element if its namespace URI is the standard URI for XSLT elements
or if its namespace is identified in the
xsl:extension-element-prefixes attribute of a containing literal result element, or in the
extension-element-prefixes attribute of the xsl:stylesheet element.
If the xsl:fallback element appears in
any other context, it is ignored, together with all its child and descendant elements.
There are no attributes.
If the parent element can be instantiated and processed, the xsl:fallback element
and its descendants are ignored. If the parent element is not recognised of if any failure occurs
instantiating it,
all its xsl:fallback children are processed in turn. If there are no xsl:fallback children, an
error is reported.
