How do you write an interactive application

I want to write down a thick client multi user application in Java. This is a typical accounting solution such as QuickBooksPro /Money.

Multiple Users can simultaneously view reports and enters bill and invoices, record payments etc. etc. It is extremely important that the views of the users are updated as soon as the underlying data is modified. For example if User A is viewing list of all the payments made on some date and user B records a new payment in that date, it should be immediately updated in User A's view automatically as it happens in QuickBooks etc.

Also, Suppose a user is entering an Invoice. He is entering various items in the details and Total Amount and Tax Amount is automatically being calculated and shown on the bottom of the form. The calculation of Tax is being done on the basis of tax criteria fed in some other table. I would like this calculation logic to reside on the middle tier so that changes can be easily done and all the clients get updated information automatically. If it is so, How will this be handled in my clients interface. Also it is possible that some other user 'B' modifies the tax rate for some item on the basis of which a user 'A' was being shown the tax amount in his interface. This will require the interface of User A to be updated to reflect the new tax amount.

I feel this is a very common requirement for people who are dealing in such software. What is the recommended architecture to be adopted for design of such applications. Please refer me some resources where I can find details. Are there any special tools available for such a requirement which act as a layer over the database and fires events which can be listened by the client interfaces so that they can be notified of changes in underlying data.

Thanks in advance.

Puneet Received on Fri Nov 09 2001 - 02:51:55 CST