+The main novelties of this version are the elimination of some cast operators
+(producing a substantial simplification in the query structure and semantics,
+see \secref{Operational}), a clear distinction between the core language and
+the auxiliary functions of the basic library, a support for query generating
+functions, the possibility of extending the language adding new libraries of
+functions and a more uniform textual syntax.
+{\MathQL}.4 incorporates the features of {\MathQL}.3 not documented on paper%
+\footnote
+{See the ``what's new'' section of {\MathQL} Web Site:
+\URI{helm.cs.unibo.it/mathql}.}
+and adds some new features improving {\MathQL} capabilities to post-process
+the query results.