XPath Functions 

You can use XML Path Language (Xpath) functions to refine XPath queries and enhance the programming power and flexibility of XPath.

The functions are divided into the following groups.

Node-Set	Takes a node-set argument, returns a node-set, or returns/provides information about a particular node within a node-set.
String	Performs evaluations, formatting, and manipulation on string arguments.
Boolean	Evaluates the argument expressions to obtain a Boolean result.
Number	Evaluates the argument expressions to obtain a numeric result.
Microsoft XPath Extension Functions	Microsoft extension functions to XPath that provide the ability to select nodes by XSD type. Also includes string comparison, number comparison, and date/time conversion functions.

Each function in the function library is specified using a function prototype that provides the return type, function name, and argument type. If an argument type is followed by a question mark, the argument is optional; otherwise, the argument is required. Function names are case-sensitive.