Re: [rules-users] Flow and Rules Together - Best practice question
Nice post, Gerret. Cean logic, nicely presented. Separation of concerns vs tangled web of dependencies. whooo! On Thu, Feb 18, 2010 at 3:05 AM, Gerret Hansper wrote: > Hi Mike, > > I have been working with Drools for only a few months now and am still > rather > new to it, but we've have made the same experience, switching from rules > only to > rules with flow, and I'm certain it's the right way to go. > > The performance implications you mention depend mainly on the way the rules > are > set up, I guess. > That is, if you have expensive RHS expressions like eval() you might indeed > profit from keeping your glucose-level condition at the beginning of the > rules > which would prevent those expressions from being reevaluted, as far as I > understand. > If you don't I can hardly imagine that activating the rules makes up a > noticeable fraction of the overall time of your process. > > We here have a scenario where some rules may be activated only if the user > starting the session has got corresponding privileges. > Since determining the priviliges is not always trivial we definitely wanted > to > have that logic in one place. The first thing to do was to use inference > (http://docs.codehaus.org/display/LOGICABYSS/Policy+Encapsulation) but > still > already with a few dozen rules and including other constraints the rule > RHsides > became rather cluttered. Moreover it was getting increasingly complex to > control the order in which the rules fired, maintanance being another > issue. > > Using a rule flow we have achieved really good separation of concerns: A > rule's > RHS mostly contains exactly those conditions that apply to its intent, none > of > the cross-concerns or technicalities. (Hey, what about an AspectDrools > implementation? ;-) ) > I am confident that OO lessons apply here, too: If you have a clean design > and > performance problems start to show up you are much more likely to solve > them > than if you have a tangled web of dependencies. > > Greetings, > Gerret > > > ___ > rules-users mailing list > rules-users@lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > ___ rules-users mailing list rules-users@lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users
Re: [rules-users] Flow and Rules Together - Best practice question
Hi Mike, I have been working with Drools for only a few months now and am still rather new to it, but we've have made the same experience, switching from rules only to rules with flow, and I'm certain it's the right way to go. The performance implications you mention depend mainly on the way the rules are set up, I guess. That is, if you have expensive RHS expressions like eval() you might indeed profit from keeping your glucose-level condition at the beginning of the rules which would prevent those expressions from being reevaluted, as far as I understand. If you don't I can hardly imagine that activating the rules makes up a noticeable fraction of the overall time of your process. We here have a scenario where some rules may be activated only if the user starting the session has got corresponding privileges. Since determining the priviliges is not always trivial we definitely wanted to have that logic in one place. The first thing to do was to use inference (http://docs.codehaus.org/display/LOGICABYSS/Policy+Encapsulation) but still already with a few dozen rules and including other constraints the rule RHsides became rather cluttered. Moreover it was getting increasingly complex to control the order in which the rules fired, maintanance being another issue. Using a rule flow we have achieved really good separation of concerns: A rule's RHS mostly contains exactly those conditions that apply to its intent, none of the cross-concerns or technicalities. (Hey, what about an AspectDrools implementation? ;-) ) I am confident that OO lessons apply here, too: If you have a clean design and performance problems start to show up you are much more likely to solve them than if you have a tangled web of dependencies. Greetings, Gerret ___ rules-users mailing list rules-users@lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users
[rules-users] Flow and Rules Together - Best practice question
Have been working solely with rules and have now created an overall rule flow that has enabled me to eliminate parts of the conditions of many rules, because the rules are in rule flow groups. For example, if the glucose value must be below 40 to get into a rule flow group called "Below 40", then I do not need to check that the glucose is below 40 in the condition of every rule in the group. I have noticed, however, that when a fact is inserted, it appears to activate all rules for which the conditions match, even though the majority of the rules are not in the rule flow group. I am interpreting this as simply activating everything applicable, taking advantage of the Rete, and then the activated rules are filtered by rule flow group. Is this a correct interpretation? The corollary question is whether I am using best practice by eliminating "redundant" conditions from my rules, or whether I should include in those conditions the constraints that were determining whether the rule flow group becomes active. If this scaled up to one to two thousand rules, would the activations and filtering be more costly? Thanks for any advice. My colleagues and I were very happy to eliminate the redundant conditions because it makes our rules look simpler, but now concerned may be going down wrong track. - Mike ___ rules-users mailing list rules-users@lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users
