Hi,

I would like upgrade my framework to have n-tier capabilities, for now 3 tier will do. I have a few initial questions:

1) I know I need to create a Class (custom type class?) as the Business Object for the business rules.

2) I need to choose a way to transfer data back and forth between the presentation layer, the business layer(middle tier) and the data layer.
I can use either XML or ADO recordsets, maybe some other technology,what is the suggested method to handle the data? XML? ADO?

3) I will need to instantiate this class when I open my forms.
Let's say it's a customer data entry screen. Basically the screen will function like this(assume we gonna use XML):

* Instantiate the business layer class (oBusiness for this example)

* Get the record.
- oXML_Record = Thisform.oBusiness.Get_Record("Select * from customers WHERE nCust_id = 54")
(The "oBusiness.Get_Data" method will issue a call to the database, get the results and put them in XML format and send the result back to the presentation layer.)

* If it's foxpro interface I can convert the XML to a cursor and bind to the controls.

* Save Record.
- Convert cursor to XML if foxpro interface
- Thisform.oBusiness.Save_Record(oXML_Object)
- How can I check for field changes? Keep a copy of the original XML on the business layer and when the business layer receives back the XML from the presentation layer compare against it?
- Call data validation method
aFailedFields = Thisform.oBusiness.Validate(oXML_Object)
(send the XML, the business object will validate and return an array with the fields that failed the validation)

* Add Record
- oXML_record = Thisform.oBusiness.Add_Record("Select * FROM Customers WHERE 1=2")
(it would return nothing but it will enable me to create the cursor based on the XML structure when I convert, so I have an empty cursor)

* Delete Record
- Thisform.oBusiness.Delete_Record(nCust_id)

* Cancel Changes
- oXML_Record = Thisform.oBusiness.Get_Record("Select * from customers WHERE nCust_id = 54")
(just call the same procedure as when getting the record)

- if I'm updating multiple tables in this screen then have a business layer object for each table that I'm updating?

Am I in the right direction?

Thanks!