[Seaside] Updating sub-components: where?

[Martin J.Laubach]

   Is there a method that is called before a page is being built? I want
to update the visual state of my component depending on some global 
session
state, possibly changing/adding some subcomponents.

   I'm currently doing that in #children, but (a) that is called twice (I
guess once for the redirect, once for the real page), and (b) it 
probably
(most certainly?) is not what was intended for #children.

   Where to do that?

	mjl