[rules-users] Sequential rules algorithm

[Mark Proctor]

I mean't emulate the performance advantange, not the behaviour. Btw it's 
JBoss Rules, or for shorthand JBossRules/JBRules, think ilog might get 
upset if we start calling ourselves JRules :)

I don't believe that sequential mode in either Advisor of JRules is 
aimed at allowing you to specify the fine grained order of each rule 
execution, although ofcourse you could do this with salience, instead 
its more about fast performance execution - there is no agenda, less 
state stored and no support for first order logic - which is a very 
common use case for decision based services. As always if you need to 
control the execution order of each and every rule, you probably 
shouldn't be using a rule engine.

Mark
Hamu, Dave 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 4.0 
> development path.
>  
> Thanks
> Shahad
>  
>  
> ------------------------------------------------------------------------
>
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