XPath 2.0 introduced many new features XQuery-cośtam:
                            - Added support for all XML simple types
                            - Many new functions (trippled instruction count)
                            - All expressions evaluate to sequence
                            - Introduces conditional expressions and for-loops
                        
XPath 3.0
                            - Dynamic function calls (function may be called without being referenced by name (find
                            function in collection and call)
                            - Inline functions
                            - Namespace literals - Namespace may be embeded into function name
                            - Support for union types - collections containing elements of different types
                            - Mapping operator - '!' performs evaluation for each element in sequence and
                            concatenates results
                            - Introduced maps 
                        
XPath 3.1
                            - New operator for function chaing '=>' 
                            - Introduced maps that store data in pair 'key:value' - 'map{ key : value, key : value
                            }'
                            - Introduced arrays - they differ from sequences in that they can be nested 'array{1, 5, 7,
                            (10 to 20)}'