RE: MVC Architecture and transactions

From: Nathan Andelin

Joe P. wrote:
You know, in the case of banking transactions, I would have
written the system in such a way that prior to posting a transaction,
I would ALLOCATE the funds.

However if you allocate against a balance, keep in mind that you also must
provide for events that can and will remove the allocation, or override
it, which may not be easy to decide - or track. What if a customer calls
to complain against what they consider to be wrongful allocations against
their credit limit?

Furthermore if an allocation is based on work in process at the teller
window, would that be a reason for kicking out exceptions in the daily
check-clearing procedure, which may be occurring at the same time? Or
would it be easier to allow the checks to clear and have the teller
address the potential rollback that could occur during the over-the-
counter posting procedure? Which takes precedence (work-in-process or
daily-batch postings)? It may be easier to resolve the potential teller
rollback while the customer is right in front of you.

Man. I think we need a basic application design discussion here. I was
talking about doing allocations during the transaction verification stage:
that is, after the teller has already hit the submit button. Not during
work in process, but once the transaction has already passed the human
edits. At this point, you begin allocating funds from each account to be
sure as part of the pre-posting edit process. If you can't allocate all the
funds, you tell the operator. (Yes, you could use this same allocation
process during operator entry, but that has all the design issues you
outline.)

Now, an alternative is to "make" the posts under commitment control, and
then roll them back if you encounter a difficulty. That's probably a
perfectly reasonable alternative and I think one of the few situations that
I consider a good use of CC.

And as always, this is my opinion. If you read my caveats and decide you
still want to use CC, then by all means do so. But I don't like to
recommend a technology unless I think it adds value, and CC doesn't always
add value.

Joe