Thanks for the depth of your reply. We're actually in the process of identifying ways in which we can improve the registration and payments process; additionally, we have already made some improvements in our development version of OCS that will be present in the next major release. I'll address the three points individually:
[*]to add more events to their initial registration and give notices to admins when registration are changed
This can be a problem in different ways whether you are using Paypal or Manual payments:
If you use the manual payment method, so long as the Conference Manager doesn't mark a registration as paid, users can change their registration type; the Conference Manager will also receive an email notification that they've changed their registration type (at the moment this is the same email that's sent out when they first choose a registration type). There is nothing to mark that the user has changed their type in the list, but Conference Managers should be checking their received payment against the registration type on the list before marking the registration as paid. Once the registration is marked as paid, the user can't make any further changes, and will have to contact the Conference Manager for changes.
However, if you are using Paypal, no notification email is sent. This can be confusing, and possibly a problem as users can actually pay for one kind of registration, and still complete further payment processes until the Conference Manager 'locks' their registration by marking it as paid. One solution to this would be to have the Paypal payments method automatically mark a registration as paid, but that doesn't solve the problem of partial payments, upgrading one's registration, etc.
It is probably beyond the scope of our software, at least for right now, to allow for incremental upgrades or partial payments, via Paypal or manually; but one possible workaround could be a 'registration notes' feature, where a Conference Manager can track any issues about a specific registration from the registration list. Would this suffice?
We have also added the ability to specify a la carte items to registrations (see http://pkp.sfu.ca/bugzilla/show_bug.cgi?id=3806
), although a stock install of OCS 2.1.1 will not include this and you will have to apply the relevant patch. Currently, users can only purchase a la carte items (banquets, etc.) in conjunction with a registration, but perhaps allowing them to purchase them through the system post-registration would be a reasonable enhancement.
[*]generate invoicing each time a registration changes so it can be paid
Would this be solved by the system generating a notification email every time a user registers or re-registers, regardless of payment method?
[*]keep track of everything someone pays for
Again, the record-keeping can probably be stronger here. The aforementioned notes feature might cover this.
Again, thanks for your comments. While I can't really offer any specific solutions for you now, I'd appreciate any further comments you might have on what I just wrote, so that I can look at how best to suggest future enhancements to the payment system. Additionally, I will be passing this thread on to the team for discussion.