... IProductDao, define the interface between the Business Layer and the Data Layer. The Business Layer does not know anything about data access and the three database Copyright © 20 06 , Data & Object ... Pattern Framework 2. 0 TM by Data & Object Factory www.dofactory.com Copyright © 20 06 , Data & Object Factory All rights reserved. Copyright © 20 06 , Data & Object ... different layers including some of the design patterns that are involved in this layering. Copyright © 20 06 , Data & Object Factory. All rights reserved. Page 22 of 66 Design...