I am trying to figure out best practice for N-Tier application design. When designing the objects my UI needs and those that will be persisted in the DB some of my colleagues are suggesting that the objects be one in the same. This doesn't not feel right to me and I am ultimately looking for some best practice documentation to help me in this decision.

I honestly do not understand why I would want to design this way given that other applications may want to interact with my Data Access Layer....or it is just ignorance or lack of understanding on my part.

Any documentation, information you could provide would be greatly appreciated. Just want to better understand these concepts and I am having a hard time finding some good information on the best practice for implementing these patterns (Or it is right in front of me on what I found and I didn't understand what was being outlined).

Thanks,

S