The Free On-line Dictionary of Computing (30 December 2018):

XML Template Pages

    (XTP) JSP transformed by XSL stylesheets.
   An XTP page is basically a JSP page which specifies an XSL
   stylesheet.  The XSL specifies how selected tags in the XTP
   page should be rewritten.  All other tags are passed through
   unchanged and so treated as standard JSP.  JSP programmers can
   use XTP used as an easy introduction to XSL, incrementally
   applying styles to their pages.

   Caucho (http://caucho.com/resin/ref/xtp.xtp).

   (2003-07-13)