Well, one mathematically right thing to do is to make a new node descending from both other nodes representing E = (P and not P) and then observe not E.
Did you read the first tutorial? Do you find the process of belief-updating on causal nets intuitive, or do you just understand the math? How hard would it be for you to explain why it works in the language of the first tutorial?
Strictly speaking, causal networks only apply to situations where the number of variables does not change, but the intuitions carry over.
Thats what I try to do, the problem is I end up observing E to be true. And E leads to an "everything" node.
I'm not sure how well I understand the math, but I feel like I probably do...
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