As XSL does not provide uppercase, lowercase, "filter accents" (and so on) methods, many projects define their own functions, always as XSL templates, sometimes duplicated across plugins and stylesheets.

It should be interesting to have a XSL helper functions library/stylesheet. XSL functions can be directly specified using the functions module in EXSLT : functions are easier to use, much less verbose, and can be used in XPath predicates.