XPath Datatypes (XSLT)

3.4. XPath Datatypes

An XPath expression returns one of four datatypes:

node-set: Represents a set of nodes. The set can be empty, or it can contain any number of nodes.
boolean: Represents the value true or false. Be aware that the true or false strings have no special meaning or value in XPath; see Section 4.2.1.2, "Boolean examples" in Chapter 4, "Branching and Control Elements" for a more detailed discussion of boolean values.
number: Represents a floating-point number. All numbers in XPath and XSLT are implemented as floating-point numbers; the integer (or int) datatype does not exist in XPath and XSLT. Specifically, all numbers are implemented as IEEE 754 floating-point numbers, the same standard used by the Java float and double primitive types. In addition to ordinary numbers, there are five special values for numbers: positive and negative infinity, positive and negative zero, and NaN, the special symbol for anything that is not a number.
string: Represents zero or more characters, as defined in the XML specification.

These datatypes are usually simple, and with the exception of node-sets, converting between types is usually straightforward. We won't discuss these datatypes in any more detail here; instead, we'll discuss datatypes and conversions as we need them to do specific tasks.