[rules-users] Sequential rules algorithm

[Shahad Ahmed]

Dave,

Thanks for the suggestions. I think giving each rule in the sequence the
same activation-group (I may have incorrectly said agenda-group in my
original email) would be a bit like the semaphore you described. When one
rule in an activation-group fires then all the other rules in the group are
disabled. I'll give this a try and see what the performance is like.

I'm actively looking into what would be involved in adding a sequential mode
to Drools. I've been using commercial rules engines like Ilog JRules in
various projects for a couple of years, but the latest addition to Drools
such as a BRMS and Ruleflow (with GUI) has definitely made me take Drools
much more seriously as a "contender" in the business rules space.

Regards,
Shahad


On 5/11/07, Hamu, Dave <Dave.Hamu at avnet.com> wrote:
>
>  Shahad,
>
> In addition to using salience, you would also need to use a semaphore.  I
> am not sure JBoss (Mark P., et. al.) have implemented a "sequential mode"
> which is a feature that is provided by both JRules and Blaze Advisor (among
> others); however, that would be a nice feature to add to the rules engine.
> It seems that without massive changes to the product, they could allow a
> rule-base to be loaded with a "sequential-mode" property in which case, the
> RETE engine would be disabled.
>
> I'm not really up to speed on the LEAPS feature and whether it is being
> obsoleted...
>
> However, I just read Mark's response and I respectfully disagree... I
> believe that you can simulate sequential processing with salience and a
> semaphore.  Basically, if the rules in question have a salience order and
> the working memory is changed using a semaphore construct, then any
> subsequent rules beyond the first rule that fires would not execute.
>
> So, if I understand the issue that you have, say that there are many
> thousands of rules, but you want them evaluated in a specific order.  Once
> the first rule fires, you can mark the data as processed and preclude the
> execution of any additional rules.
>
> There may be other issues from a performance perspective, but ultimately,
> I think that this workaround is very doable.
>
> On the other hand, I applaud Mark's suggestion to have a member of the
> JRules community take the lead on a sequential-mode algorithm for JRules
> 4.0...  I have been a fan of the Drools/JRules project since the 1.x days
> and I have witness this project evolve from an intriguing tool-kit to a
> impressive product and I think that your suggestion is fantastic.  Providing
> this additional feature will further position JRules as a leading contender
> in the Business Rules space.
>
> Regards,
>
> Dave
>
>  ------------------------------
> *From:* rules-users-bounces at lists.jboss.org [mailto:
> rules-users-bounces at lists.jboss.org] *On Behalf Of *Shahad Ahmed
> *Sent:* Friday, May 11, 2007 8:34 AM
> *To:* rules-users at lists.jboss.org
> *Subject:* [rules-users] Sequential rules algorithm
>
>
>  Does anyone know if there's an efficient way of replicating the Ilog
> JRules sequential algorithm in Drools?
>
> From a (over simplified) users perspective, the JRules sequential
> algorithm takes an ordered list of rules and fires the first rule in the
> sequence with a valid IF condition. You can also specify a maximum number of
> rules in a sequence that may fire. If you have a large number of simple
> rules to be fired in sequence (often precondition validating rules in a
> complex ruleflow), then the sequential algorithm gives a significant
> performance gain over the RETE algorithm in JRules.
>
> I can see how you might order a set of rules by salience and give then the
> same agenda group. Then I assume you will get the equivalent "behaviour" to
> the Ilog sequential algorithm described above. However, before I try this
> out, I thought I'd ask if anyone has a view on the performance of this
> approach; and whether there would be anything to be gained by adding a
> similar sequential algorithm to Drools.
>
> I've seen a few Blog posts in the past that suggest that the Ilog
> sequential algorithm is similar to LEAPS, but I don't know if that's
> accurate - also LEAPS will no longer be supported on Drools 4.0development path.
>
> Thanks
> Shahad
>
>
>
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