xsltc is short for the compiled working mode of (at least) the xalan xslt processor
Unfortunately xalan in compiled mode behaves differently from xalan in interpreted mode. If you do not want headaches, either try your stylesheets in compiled mode often, or forget compiled (or better: all) xalan. There are better xslt processors, like saxon. Some of the problems I have encountered with xsltc (taking two workdays to get a stylesheet which works properly in interpreted mode to work buggy in compiled xalan):
- node-set() behaves differently
- cannot cope with xpath expressions with multiple indirections (try nested fors instead)
- distinct() does not work