public boolean isImpliesOrder() {
    return impliesOrder;
  }
Property for indicating that the function is a window function and an OVER clause is required when invoked.
example:
SELECT val, rank() OVER (ORDER BY val DESC) FROM t_table;
@return true if the function is a window function, false otherwise
ql/src/java/org/apache/hadoop/hive/ql/exec/WindowFunctionInfo.java