I'm about to start a new project and want some advice on how to implement.

I need a web application which contains a booking module for reserving timeslots, and a time management module which will enable employees to clock in / clock out.

If I am writing an update to the time managment module, I don't want to disrupt the booking engine availability by releasing a new solution containing both modules.

to make things more difficult, there is some shared functionality like common users, roles and security.

Here's a suggestion I've gotten, which sounds a bit cruddy, but may be functional. Write a 'container' web application which consists of basically a frame, and authentication / security features. This then has links which, will load the 2 independantly built and released web applications into the frame.

I can see that say, if I wanted to update the time management module, I would only need to build and release this separately, and the rest of the solution would be 'untouched'

Any better alternatives?