guideline

Use access types to class-wide types to implement heterogeneous polymorphic data structures.

Use tagged types and type extension rather than variant records (in combination with enumeration types and case statements).

An array of type Employee_List can contain pointers to part-time and full-time employees (and possibly other kinds of employees in the future):

-----------------------------------------------------------------------------------
package Personnel is
   type Employee  is tagged limited private;
   type Reference is access all Employee'Class;
   ...
private
   ...
end Personnel;
-----------------------------------------------------------------------------------
with Personnel; 
package Part_Time_Staff is
   type Part_Time_Employee is new Personnel.Employee with 
      record
         ...
      end record;
   ...
end Part_Time_Staff;
-----------------------------------------------------------------------------------
with Personnel;
package Full_Time_Staff is
   type Full_Time_Employee is new Personnel.Employee with
      record
         ...
      end record;
   ...
end Full_Time_Staff;
-----------------------------------------------------------------------------------

... 

type Employee_List is array (Positive range <>) of Personnel.Reference;

Current_Employees : Employee_List (1..10);

...

Current_Employees(1) := new Full_Time_Staff.Full_Time_Employee;
Current_Employees(2) := new Part_Time_Staff.Part_Time_Employee;
...

rationale