Function calls are another building block of queries. A typical function call might look like:

substring($prodName, 1, 5)

where the name of the function is substring and there are three arguments, separated by commas and surrounded by parentheses. The first argument is a variable reference, whereas the other two are numeric literals.

The XQuery language has over 100 built-in functions, detailed in Appendix A. Chapter 8 explains the details of how to read function signatures and call them. It also explains how to define your own functions.