Process pages values before the hit the model

[richardchaven]

I'm starting with InstantRails with a background in OOP (Object Pascal,
Java, etc.).

I am creating an application that allows the user to enter multiple
values that will each become a tuple in the database table. Where do I
put the code that examines and manipulates the values entered on the
HTML page ?

I prefer not to put them on the controller action of the "next" page
because I want to use AJAX to support a single-page application.

I'm also looking for a process flow diagram that show how control
passes from one part of the Rails framework to another. I also welcome
any book recommendation that deal with the concepts of Rails rather
than a cookbooks.

TIA