I'm trying to develop application with separation of UI/BL/DAL.
I have read a lot of theories and I'm trying to develop a blue print for my application.
I have no problem in UI thing. But I have problem with designing Data Access Layer.
It will basically be a SQLite database backend (I may add other backends as well as XML).
Now I don't know how to write class(es) to do the DAL. So please help me get on it, perhaps with very simple example.


Since no body have answered, I will pretend it to be unclear, let me get to the heart where I hit a wall. I know how to get stuffs from DB, and I know how to use them (In normal app) but have never done UI-BLL-DAL application and I was wondering how I can implement that. Main issue is what should BLL send and what should DAL return.

Many articles just say I should not send queries/concatenated query strings and they don't say what should I do as alternative. They talk about structure but i'm yet to find an article on how to actually d it.

Many examples are .Net specific, ADO.NET etc. I cannot find any example in C/C++ or Python, PHP which I'm conversant

If You have not understood my question/point I'll be happy to clarify