onmouseovereffect attribute VS. effect attribute

I have read through the ICEfaces docs, but I cannot find where it is specified exactly what is supposed to happen when you use the onmouseovereffect attribute (for example) as opposed to when you use the regular “effect” attribute.

In the developer’s guide it just shows using the effect attribute bound to a getter/setter in the backing bean, but when I use this attribute, nothing happens. When I use the onmouseovereffect though, the effect occurs when I move the mouse over the component as expected.

What is supposed to happen when you use the regular effect attribute? Are extra steps required when using it?

Thanks,
Kurzweil4