I put together an example of using XPages to update data from multiple forms on a single XPage. There is a sample database for you to download as well as a presentation that walks you through the steps involved.
XPages separates the presentation layer from the data layer. This is obviously very different to the one to one relationship in Domino. XPages also allows the developer to bind to multiple datasources from a single page. This feature can really provide a different approach to developing Domino applications.
I came up with the following simple use case: We have an application where the user takes product orders that are shipped to customers. Sometimes the user needs to update the customer information while taking the order. We can provide the Customer fields right on the Order form and bind them via a Panel control to the Customer form. A single button with a simple action saves all the bound datasources for the page and therefore updates both forms for us. Here is a screen shot:
Want to read more? See John Mackey's blog