Re: [rules-users] Chart notation, update, and infinite loops

From: Edson Tirelli <tirelli(a)post.com&gt; Subject: Re: [rules-users] Chart notation, update, and infinite loops To: "Rules Users List" <rules-users(a)lists.jboss.org&gt; Date: Tuesday, November 4, 2008, 7:06 PM Dan, This is a feature that is in our to-do list. Jess calls it "slot specific updates". We did not had the time yet to implement it though. :( []s Edson 2008/11/4 Dan Seaver <dan.seaver(a)ge.com&gt; > > Your understanding is very close to what I'm looking for. I don't mind > having > multiple rule activations in other areas of the ruleset when the Fact is > updated, I just don't want the current rule, the one with the update > statement, to be reactivated. > > Accumulate plus no-loop works fine for the specific case of updating > amounts, but I'd like to have something generic for more sophisticated > logic > that would be implemented in the "then" clause. > > Maybe if there was something that looked specifically at each property of > the update? In this case, the "when" clause is looking at the "name" > property and the "then" clause is updating the "amount" property. As the > "name" is not being changed, then the update wouldn't reactivate the rule. > > > > Greg Barton wrote: > > > > If you have the control fact that handles the "applied == false" > condition > > you wouldn't need to prevent reactivation of the rule. It would be > > handled by the condition. > > > > I'm thinking Edson's accumulate suggestion would be best, at this point. > > > > If I understand correctly, what you want is this: > > > > 1) One rule Fact/Charge activation per Charge instance, with no > > reactivation when the Fact is updated. > > 2) Other Fact dependent rule activations when the Fact is updated. > > > > The problem with making (1) happen is that you'd still have the matched > > Fact being updated once per Charge, which could lead to reactivation of > > the rules in (2) multiple times, which you may not want. If you use > > accumulate in the Fact/Charge rule, plus no-loop to prevent reactivation, > > you get the best of both worlds: single activation of the Fact/Charge > > rule, with a single update to notify other rules that the Fact has > > changed. > > > > I think what you're after is some kind of "modify group," where multiple > > calls to modify are counted as just one, and rules are notified when the > > group is closed out. I'm not sure how that would be implemented, because > > how do you know when the modifications are finished? A low priority > rule, > > possibly? Anyway, it doesn't exist in drools, afaik. > > > > You could do that kind of thing with an additional rule that tests for > the > > nonexistence of an unprocessed Charge, then does the update. Adding in > > the control fact for tracking Charges: > > > > rule "Update Amount" > > when > > amountFact : Fact(name == "Amount") > > $charge : Charge() > > chargeTracker : ChargeTracker(charge == $charge, applied == false) > > then > > Double amount = amountFact.getAmount(); > > Double chargeAmount = charge.getAmount(); > > amountFact.setAmount(amount + chargeAmount); > > chargeTracker.setApplied(true); > > update(charge); > > end > > > > rule "Close Facts After Charges Applied" > > no-loop false > > when > > amountFact : Fact(name == "Amount") > > not ChargeTracker(applied == false) > > then > > update(amountFact); > > end > > > > You'd probablt also have to prevent the "Close Facts" rule from firing > > when there's just no ChargeTrackers in working memory, too. > > > > Give that a try. > > > > --- On Tue, 11/4/08, Dan Seaver <dan.seaver(a)ge.com&gt; wrote: > > > >> From: Dan Seaver <dan.seaver(a)ge.com&gt; > >> Subject: Re: [rules-users] Chart notation, update, and infinite loops > >> To: rules-users(a)lists.jboss.org > >> Date: Tuesday, November 4, 2008, 1:55 PM > >> Greg, > >> 1) Yes, in this case I'm looking for the cartesian > >> join. > >> 2) No, I can't add a property to Charge as it's > >> part of our corp Object > >> Model. > >> > >> However, I could create a third object that manages whether > >> the Charge has > >> been processed which works just fine. Unless there is a > >> simpler strategy / > >> technique, I'll go with that. > >> > >> Do you know of any way to keep the rule from being put back > >> on the agenda > >> when amountFact is updated? I want other rules to know that > >> it's been > >> updated, just not the rule that made the change. > >> > >> Dan > >> > >> > >> Greg Barton wrote: > >> > > >> > 1) Do you want to apply all Charges in working memory > >> to all "Amount" > >> > Facts? I ask because the rule is a cartesian join > >> (i.e. no relation > >> > between matched objects) and that sometimes performs > >> in ways users don't > >> > expect. (i.e. all combinations of objects that match > >> the conditions are > >> > affected by the rule) > >> > 2) Can you add a property to the Charge object? Then > >> you could use a > >> > boolean named "applied" to prevent future > >> matches. > >> > > >> > Rule "Update Amount" > >> > when > >> > amountFact : Fact(name == "Amount") > >> > charge : Charge(applied == false) > >> > then > >> > Double amount = amountFact.getAmount(); > >> > Double chargeAmount = charge.getAmount(); > >> > amountFact.setAmount(amount + chargeAmount); > >> > update(amountFact); > >> > charge.setApplied(true); > >> > update(charge); > >> > end > >> > > >> > If a charge could be applied to multiple Facts you > >> could maintain an > >> > "appliedTo" list of Facts in the Charge, and > >> check that instead of a > >> > simple boolean. > >> > > >> > --- On Tue, 11/4/08, Dan Seaver > >> <dan.seaver(a)ge.com&gt; wrote: > >> > > >> >> From: Dan Seaver <dan.seaver(a)ge.com&gt; > >> >> Subject: [rules-users] Chart notation, update, and > >> infinite loops > >> >> To: rules-users(a)lists.jboss.org > >> >> Date: Tuesday, November 4, 2008, 11:50 AM > >> >> I'm trying to find a good technique for > >> updating > >> >> specific facts in working > >> >> memory. What I'm currently doing is something > >> like > >> >> this: > >> >> > >> >> Rule "Update Amount" > >> >> when > >> >> amountFact : Fact(name == > >> "Amount") > >> >> charge : Charge() > >> >> then > >> >> Double amount = amountFact.getAmount(); > >> >> Double chargeAmount = charge.getAmount(); > >> >> amountFact.setAmount(amount + chargeAmount); > >> >> update(amountFact); > >> >> end > >> >> > >> >> The update statement causes an infinite loop. > >> >> I tried using no-loop, which works if there is 1 > >> charge, > >> >> but not if there > >> >> are more than one. > >> >> > >> >> Any help with solutions or strategies would be > >> much > >> >> appreciated. > >> >> -- > >> >> View this message in context: > >> >> > >> > http://www.nabble.com/Chart-notation%2C-update%2C-and-infinite-loops-tp20... > >> >> Sent from the drools - user mailing list archive > >> at > >> >> Nabble.com. > >> >> > >> >> _______________________________________________ > >> >> rules-users mailing list > >> >> rules-users(a)lists.jboss.org > >> >> > >> https://lists.jboss.org/mailman/listinfo/rules-users > >> > > >> > > >> > > >> > _______________________________________________ > >> > rules-users mailing list > >> > rules-users(a)lists.jboss.org > >> > https://lists.jboss.org/mailman/listinfo/rules-users > >> > > >> > > >> > >> -- > >> View this message in context: > >> > http://www.nabble.com/Chart-notation%2C-update%2C-and-infinite-loops-tp20... > >> Sent from the drools - user mailing list archive at > >> Nabble.com. > >> > >> _______________________________________________ > >> rules-users mailing list > >> rules-users(a)lists.jboss.org > >> https://lists.jboss.org/mailman/listinfo/rules-users > > > > > > > > _______________________________________________ > > rules-users mailing list > > rules-users(a)lists.jboss.org > > https://lists.jboss.org/mailman/listinfo/rules-users > > > > > > -- > View this message in context: > http://www.nabble.com/Chart-notation%2C-update%2C-and-infinite-loops-tp20... > Sent from the drools - user mailing list archive at Nabble.com. > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > -- Edson Tirelli JBoss Drools Core Development JBoss, a division of Red Hat @ www.jboss.com _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users