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From: "Mikito Harakiri" <mikharakiri_nospaum@yahoo.com>
Newsgroups: comp.object,comp.databases.theory
Subject: Rule engines
Date: 6 Jun 2006 09:46:08 -0700
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Patrick May wrote:
> "Mikito Harakiri" <mikharakiri_nospaum@yahoo.com> writes:
> > > Not every business rule can be expressed in (even a complex)
> > > formula. Ever heard of rule based systems?
> >
> > What about them? Rule based systems are extremely goofy way to
> > program business rules. No exceptions, no arithmetics, no
> > loops. Rule firing order is nondeterministic. I would prefer an
> > implementation in traditional programming language to rule based
> > system any day.
>
>      While your summary is correct for Rete based rules engines, I
> recently saw a demo by ILog that showed how they have extended the
> basic algorithm to allow grouping of rules into sets that can be
> applied in order and based on decision points.  It really blurs the
> distinction between rules engine and programming language.
>
>      My client is considering using it to allow end users in finance
> and marketing to change rules without involving the development
> teams.  I'm curious to see how well this experiment works.

Failed to download ilog demo. Got their whitepaper "Why business
rules?" however. Let's go through examples:

Page 6, Figure 2. Business rule which can easily enforced in DBMS.

create view discountedOrder
select
    case when c.state = 'MN' and c.value = 'Gold'
            and o.date between 'jan1' and 'feb2'
    then
            sum(o.price)*0.9
    else
            sum(o.price)
    end AS total,
    ... comment
from Customer c, Order o
where c.customer_id = o.customer_id

All you need to do in application code which processes shopping cart is
to select from this view with particular order#.

Page 7, Table 2. This table is designed either by moron or a clever
salesman who deliberately made it goofy to warrant a case for "rules
engine". Why don't they have

1. A list of states with cost of living index

MD  0.5
CA  1.0
FL   0.8
.........

2. A fixed classification to Gold-Platinum-Silver

Gold    > $1000
$1000 > Platinum  > $500
Silver < $500

Then the rule of classifying cusomer into Gold-Platinum-Silver is just
taking the dollar amount, adjusting it for cost of living and checking
what bracket it falls into. Again, implemented in DBMS easly.