different types pattern

My application is based on lists of tasks. Tasks are from different types. Some types are known, others are not yet. I think future types might have different attributes.

I don’t know what is the best pattern to use here.

do you think abstraction will be the one for me? Does yii support that?

this casts some lighting, yet still unclear to me.please see the last post in the thread, http://www.yiiframework.com/forum/index.php?/topic/4069-how-to-extends-inheritance-model/