There are some pretty big plans for functions in XSLT 2.0 and XPath 2.0. In particular, the following new functions are scheduled for XSLT 2.0:
Could provide QName-aware functions to allow the namespace declarations that were in scope to be enforced.
Must add date-formatting functions, to support XML schema.
Should provide a function to make relative URIs absolute.
Must simplify grouping. In XSLT 2.0, it must be possible to group nodes based on their string values.
The following changes are planned for functions in XPath 2.0:
Must extend the set of aggregation functions, such as including min and max .
Should provide intersection and difference functions for node sets.
Should support additional string functions, such as functions for string replacement, string padding, and string case conversions.
Should support aggregation functions when applied to collections such as node sets.
Must define functions to work with XML schema primitive types.
That takes care of the functions available in XSLT and XPath for transformations. Chapter 9 explores variables , parameters, and other powerful topics.