Contrary to your usual practice of including voluminous relevant links, you didn't point to anything specific for Judea Pearl. Let's give this link for his book Causality, which is where people will find the graphical calculus you rely on.

You've mentioned Pearl before, but haven't blogged the details. Do you expect to digest Pearl's graphical approach into something OB-readers will be able to understand in one sitting at some point? That would be a real service, imho.