Presentation and behavior are both scripted at the place in question.
Remark: this is the prefered "new style" action document.
The "new style" splits transaction into
two methods.
One for the propose~ and one for the accept
part of the transaction.
The old style, using only a general write method
is depreciated.
(Be warned: due to it's restrictions,
it need create places too early.
Upon transaction retries
conflicts in OID calculation will result.
Those in turn can lock you places forever due to mutual disagreement
on current state.)