A practical introduction to EXPath
Collaboratively Defining Open Standards for Portable XPath Extensions
For some time now the demand for standardized extensions within the core XML technologies, especially XSLT and XQuery, has been increasing. A closer look at the EXSLT and EXQuery projects shows that their goals align to address the issue of extensions, but also that they overlap, predominantly because of their common ancestor: XPath. It is thus reasonable to assume that both projects should collaborate together on common areas influenced by the underlying XPath specification. In addition, by jointly working at the lower level, any XPath based language or processor could also benefit from this work, like XProc, XForms or plain XPath engines.