As of Wagn 1.14, there are three settings for configurable action extensions: *on create, *on update, and *on delete.
Rules based on these settings can be used to extend the actions with customized behaviors, most notably emails.
Suppose you're having a birthday party, and you're making your friends register for it. (You're weird.)
You create a Registration card with a bunch of structure to determine the fields they have to complete. Then, when they submit the registration, you want to receive an email to notify that they've registered.
First you create an Email template called "My Birthday Email" and set it to be delivered to you.
Then you go to "advanced > rules" on the menu of a Registration card and create a new *on create rule and add "My Birthday Email" to the list.
This means that whenever a Registration card is successfully created, you'll be emailed!
Action extension rules work like any other Wagn rules:
In this case, the interface for, say, an *on update rule is basically a standard Pointer interface, which means you're basically editing a list of cards. In this case, the list of cards is a behavior to be taken with the given event.
As of Wagn 1.14, the only built-in behavior is sending an email (see Email Template and the above example).
In the near future we expect to see mods for supporting many other kinds of behaviors, including things like "tweets", "requests", and other integrations with other software.