e.g: do not generate events of an application server when the database server is down.

Did you already have a database which was down?
If the database was monitored by zenoss, It can become a nightmare.
All your application server and so on are failing and generating events in zenoss.
To see what actually is causing the floods of events it's difficult to see.

Now there is a way to get this on the rails correctly.

This is possible using an event mapping.
Did you ever used an event mapping before?

Okay let's hit it.

navigate to the web interface to the event class where you would like the dependency.
Now click on the breadcrumb and choose  More  > Transform

This brings you to a event transform rule. It is will be called when an event comes in for that class.

Now construct an event mapping that would look like this:

if device.id == 'id_of_application_server':
    db_server = device.findDevice('id_of_db_server')
    if db_server.getPingStatus() > 0:
        evt.eventState = 2 # suppressed

In this case no event will come in if the database server is down (not responing on pings)

This can be ofcourse anything.