datamodeling question?

Great appreciation for any one who did encounter such a modeling difficulty and willing to pass me couple of recommendations. I am trying to build a data model for an outsourcing business (like payroll provider, ...). The model will be translated into Oracle. here is the difficulty:

1. the data model should support the current key structure for existing payroll system that are run by the clients (the clients are the companies that we are processing payroll for). However, each one of these clients has a different unique key to support their current systems on their local databases. For example, one have ssn as a key, another has emp_id and emp_div (char) as a pri key.
2. data will be passed back and forth between our system (we are the outsourcing company) and each one of their systems (the client).
3. Each client could have common attributes with all other clients but would like to also have unique attributes for the same entity. The existance of the unique attribute is relavant to one client only. for example, in emp a specific client want to keep track of if an employee has relatives or not or another client may want to keep track of someone height,... does that mean that I have to have subtype entity for each client. then how can I determine how the front-end (form, pb datawindow,...) would look like and what columns and relavant busniess rules to display?

I am sure that most outsourcing business dealt with this issue of desinging very flexible data model. Again any help is greatly appreciated. Received on Tue Jul 16 1996 - 00:00:00 CEST