Compare single values and sequences of single or no values:
These operators return either true, false, the empty sequence, an error, or a type exception.
Types must be comparable (No automatic conversion from strings as in XPath 1.0!):
Subtype substitution: A derived type may substitute for its base type. In particular, integer may be used where decimal is expected.
Type promotion: decimal may be promoted to float, and float may be promoted to double.