XPath Operators (XSLT)

B.4. XPath Operators

For the first six boolean operators, comparing values of various datatypes is complicated. We explain the various possibilities here:

If both objects are boolean values: Then they are equal if they have the same value. For less-than and greater-than comparisons, false is considered less than true (the function call number(false()) returns 0, while number(true()) returns 1).
If both objects are numbers: Then the operators work just the way you'd think they would.
If both objects are strings: Then they are equal if their Unicode characters are identical. For less-than and greater-than comparisons, the character codes are compared.
If neither object is a node-set and the operator is = or !=: Then the two objects are converted to the same object type, and the comparison works as described previously. If one of the objects is a boolean, then the objects are converted to boolean values as if by a call to the boolean() function. If none of the objects are boolean, the next attempted conversion is to a number. If one of the objects is a number, then the objects are converted to numeric values as if by a call to the number() function. Otherwise, all objects are converted to strings as if by a call to the string() function.
If neither object is a node-set and the operator is <, >, or >=: Then the objects are converted to numbers and compared.
If one or both of the objects is a node-set