[rules-users] Question about Rete Tree example with NotNode in "Drools JBoss Rules 5.0 Developers Guide"

[Geoff Hay]

see book errata at
https://www.packtpub.com/support?nid=4009

________________________________________
From: rules-users-bounces at lists.jboss.org [rules-users-bounces at lists.jboss.org] On Behalf Of Tina Vießmann [tviessmann at stud.hs-bremen.de]
Sent: Wednesday, 27 October 2010 1:24 p.m.
To: Rules Users List
Subject: [rules-users] Question about Rete Tree example with NotNode in "Drools JBoss Rules 5.0 Developers Guide"

Hi,

I'm working through the explanations about Rete Trees in chapter 12 of
"Drools JBoss Rules 5.0 Developers Guide" on page 264-265. I have a
problem in understanding the input of the NotNode.

The rule says:
     when
       $address : Address ( addressLine == "Rossa Avenue" )
       not (
         $account : Account ( balance < 100 ) and
         Customer ( accounts contains $account )
       )
     then
        ...

The related figure shows:
1. The Address object being processed and a tuple will be created by a
LeftInputAdapterNode.
2. The tuple of 1. will be joined with the Account fact with no
constraints (so that there's a tuple of size two?).
3. The tuple of 2. will be joined with the Customer fact with the
restriction 'accounts contains $account'. (That results in a tuple with
size 3!?)
4. The tuple of 3. will then be processed by a RightInputAdapterNode.
5. The tuple/fact from 3. will be processed using a NotNode together
with the Address-tuple from 1.

I don't understand while the tuple from 1. will in step 2 be joined with
the Account fact. I would have expected something like:
1. // same
2. The Account fact will be processed and a tuple will be created by a
LeftInputAdapterNode.
3. The Customer fact will be joined with the Account tuple with the
constraint 'accounts contains $address'. Resulting in a tuple.
4. // somehow the tuple from step 3 will be negated and joined with the
tuple from step 1.

Could anybody explain to me why it's done the way its drawn in the book?

Thank you! :)
Tina
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