XSLT and XPATH: A Guide to XML Transformations

11.1. XSLT Function Groups

XSLT function groups follow the same conventions as XPath core function groups. There are four XPath function groups aligned with the four objects they produce: node-set, string, Boolean, and number. However, there are no XSLT functions in the number function group, so there is technically no XSLT number function group.

The XSLT functions that return node-sets are: document(), which works with material from external documents; key(), which provides an index-like addressing capability; and current(), which provides a way to explicitly address the current node in a given context. These three functions are in the node-set XSLT function group.

The XSLT functions that return strings are: system-property(), which is used ...