We had similar use case. What we do is we model the Schema elements, generate Java Beans (pojo), and write rules using these Pojo. Now we have written a Service on top which takes Hibernate QL and gets the database records as the same Pojos that Rules are defined on and fire the Rules. Thus the service is generic and can be changed to take any Query. The Rules can me modified and changed anytime and redeployed but business objects in form of Pojos remain the same. Hope this helps -Uday ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Joe Chuby Sent: Friday, March 09, 2007 3:53 AM To: rules-users(a)lists.jboss.org Subject: [rules-users] Using rules with database scenario Hi all, First time trying to learn JBoss Rules here. We have a pretty large database (DBMS), we want to build some rules and retrieve data based on the rules. Could someone give a hint or an example of this usage scenario? I mean, how can I use rules for database query, without writing my rules in SQL directly? We are currently writing everything in HQL (Hibernate), but the rules change every 3 months on average, so that's not a way to maintain the system. Therefore, we want to extract that portion of the business logic out of the code. The data structure does not change, but the rules keep on changing. I'm reading the user's guide, running thru the examples, writing some of my own, but still no clue how to make it work with database. If someone could give a sample, that would be greatly appreciated. Thanks a lot.

Thanks all for replying. We currently already have a layer of service (DAO) to retrieve data from the database. We were thinking along the line you suggested there, but somehow, we have the impression that it's not quite as efficient as we would like. If we were to load the data from the database so that Rules can pick those we wanted, we would have to load records in the range of hundreds of thousands (or even more), which would kill our system there. It would be much less expensive to do this with a single query statement. Right now, we are thinking along the line of, say, letting the rules generate a query statement on the fly, based on the result from firing the rules. But that's much more complicated to achieve that just writing the SQL directly. Now, to make things more complicated (as per the business requirements), if we use rules, we have to run parts of the rules first, retrieve parts of the data, then run the second part of the rules (which use the first part of data to make decision), then retrieve next part of data, and so on. This does not seem like an efficient way though. With SQL, we could write a more or less complicated statement (with sub-queries and the usual suspect), and get the final result in one shot. The major issue we have with rules is that it assumes all data necessary for firing the rules are in memory. This works fine for small systems (and with small number of users). But right now, we couldn't figure out an efficient way to work with large amount of data already in the database. Maybe we are are not thinking in the right line of reasoning. Please help to point out what's wrong. If someone had experience dealing with large database system and is willing to share the experience, that would be really appreciated. We are currently using Rules v3.0.5. Will try the v3.1.0. Best, Marcus Ilgner <marcus.ilgner(a)gmail.com&gt; wrote: That's probably the best solution. Using the current version (3.1M1), you can use the FROM keyword to reference facts from List object returned from a method call on a service, for example. Something like this works very good in my current testing project: rule foobar when MyObject( someValue = "foobar" ) from MyObjectDAO.loadAll() then ... end The DAO then uses Hibernate to load some objects and returns a List which can be used by Drools. As Uday already wrote, you could also write a DAO which retrieves arbitrary objects using a given HQL statement. Best regards Marcus _______________________________________________ --------------------------------- No need to miss a message. Get email on-the-go with Yahoo! Mail for Mobile. Get started. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users