2.2.2 [W3C-XSLT] Section 2.1, XSLT Namespace
The specification states:
XSLT processors must use the XML namespaces mechanism [XML Names] to recognize elements and attributes from this namespace. Elements from the XSLT namespace are recognized only in the stylesheet not in the source document. The complete list of XSLT-defined elements is specified in [B Element Syntax Summary].
Only Instruction elements from the complete list of XSLT-defined elements specified in Appendix B of [W3C-XSLT] are recognized.