Correct architecture

Question

Started doing a small project: accounting for income and expenditure.

Comply with the following setting:

You must select a base

1) functionality that can be used in each
Manager (file, XML, DB)
2) to develop a class hierarchy (Basic, heir) discretion. Hierarchy
should be able to use the base class is convenient, no matter what
implementation is in use (polymorphism)
Build
3) taking into account the encapsulation classes
4) implement additional saving in file input records.


I would like to hear your criticism to you as professionals advise that so no so posted. Rewrite code I didn't ask, simply give good tips!