"Unknowns play a crucial role in the decision model: they provide a precise specification of the information resources that need to be obtained to complete the dependency chains. Unknowns are usually either values that need to be determined (externals) or relationships whose form is not known (dependencies)...

 

Another advantage of treating “assumptions” in terms of uncertainty is that the uncertainty introduced by each assumption can be propagated through the model to estimate the uncertainty of the affected outcomes."