Appendix A. Extension Functions for XPath in XSLT

While XPath includes a powerful set of basic functions, some applications of XPath need to support capabilities that go beyond that core. Currently, the most widely used XPath-based application is, of course, XSLT; aside from proprietary extensions offered through the various XSLT processors, it acquires these extra capabilities by way of two commonly used sets of extension functions. (Don't count on their availability in other XPath-based contexts, although because of their usefulness they may be adopted elsewhere as well.)

The first set of functions comes from XSLT itself, providing access to path, node, and string-value handling facilities necessary for XSLT processing. The second set of functions comes from the independent Extensions to XSLT (EXSLT) project, providing support for a variety of tasks that weren't addressed in either XPath 1.0 or XSLT 1.0.