All data is typed according to XML Schema Part 2: Datatypes.
Schema is used to specify types
If no schema is available, the default type is xs:anyType or
xs:anySimpleType
Operators and functions are type-aware; e.g. can't add a string to a double or compare an integer to a year.
Constructors and casts are are available to convert data to appropriate types
Automatic casting is performed on untyped data, but can fail