Markus,

A real life question to help me make sure I understand your points.

I have 3 separate systems that are share portions of the data.

1) There is a SQL system that collects data
2) A VFP billing system that determines a customers bill based on the collected data from (1).
3) An off the shelf accounting system that creates the invoices and tracks Accounts Receivable based on the billing data from (2).

Some of the data entry control will be contained outside the 3 above systems. The outside system will collect the basic entity data for creating new customers. Some of this data must be sent to each one of the 3 above systems.

Based on what I understand from the prior discussion, to minimize system maintenance headaches, the system that will be separate from the main 3 systems should have 2 separate parts.

A data services tier handles chores such as verifying the links between the 3 main systems. And a business logic tier that handles verifying specific information such as information entered for a new customer.

Do you have anything else to add that I should watch out for when development starts?

TIA,

PF

>> Ok then we agree :-)
>
>Gee, yeah, hm. That kinda sucks. ;-) Now we gotta find something else to argue about. (Monthy Python quote: "I'd like to buy an argument!" <bg>)
>
>Markus