Skills required for using Drools Guvnor
by Swapnil Sawant
Hi,
I had a very basic question. I wanted to know the pre-requisite skills which are required in order to start working on drools guvnor GUI.
When I say work , I mean creating rules/modifying them etc.
Technical knowledge(e.g. java technology) is must in this case?
Thanks & Regards,
Swapnil Sawant
S
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16 years, 1 month
Drools beginners guide
by Singh, Palvinder X.
I am new to Drools and just executed with my first sample program. I
have been trying to find out some beginners guide to help me in start
up, but unable to find any over the net. I would appreciate if anyone
can share some material to go thru.
Just to set up some background, I am not new to IT but yes new to
Business rule engine.
Thanks,
Palvinder Singh
16 years, 1 month
NPE in 5.1 PackageBuilder due to misspelled enum name
by Wolfgang Laun
Given an enum Fruit { CHERRY, STRAWBERRY } a rule with a typo in an enum name
Jam( fruit == Fruit.CHERIE || == Fruit.STRAWBERRY,... )
causes the NPE shown below while adding the DRL resource:
Exception in thread "main" java.lang.NullPointerException
at org.drools.rule.AbstractCompositeRestriction.getRequiredDeclarations(AbstractCompositeRestriction.java:59)
at org.drools.rule.MultiRestrictionFieldConstraint.getRequiredDeclarations(MultiRestrictionFieldConstraint.java:73)
at org.drools.rule.Pattern.setConstraintType(Pattern.java:358)
at org.drools.rule.Pattern.addConstraint(Pattern.java:226)
at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:432)
at org.drools.rule.builder.PatternBuilder.buildConstraint(PatternBuilder.java:264)
at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:213)
at org.drools.rule.builder.PatternBuilder.build(PatternBuilder.java:108)
at org.drools.rule.builder.GroupElementBuilder.build(GroupElementBuilder.java:69)
at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:79)
at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1151)
at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:637)
at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:267)
at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:459)
at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:28)
at rss.checker.engine.impl.DroolsEngine.loadSourceRules(DroolsEngine.java:49)
at rss.checker.init.Main.exec(Main.java:36)
at rss.checker.init.Main.main(Main.java:63)
16 years, 1 month
Gunvor Test Scenarios in Batch?
by Lawrence Terrill
I'd like to use Guvnor-defined test scenarios in a externally invoked 'batch' process in order to run all the tests for a given change-set or test package in an automated process rather than through the Guvnor GUI, such as when new Java code is checked in. Is there an API or other facility that supports such a thing?
Thanks!
Larry
16 years, 2 months
Getting Exception firing rule second time with same KnowledgeBase
by gauravs
Hello,
I am facing this problem which I tried to resolve in all possible ways I
could think of but situation is bit crazy here. I am creation knowledgebase
object and putting it in servetCOntext object. On HTTP Request I create a
new session, insert facts and fire all the rules. Every thing works well
first time. But repeating the same (making another HTTP Request) throws
exception shown below. If I create fresh knowledgebase every time problem
doesn't show up at all.
Please suggest where I might be going wrong. Google suggest that somewhere
object are getting null. I verified that too. It doesn't seem to be the
case.
Regards,
-Gaurav.
org.drools.runtime.rule.ConsequenceException: [Error: unable to access
field]
[Near : {... Unknown ....}]
^
[Line: 1, Column: 0]
at
org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandle
r.java:23)
at
org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:943)
at
org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:885)
at
org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1086)
at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:660)
at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:627)
at
org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:183)
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16 years, 2 months
Drools scalability
by james corrigan
Hi All,
Can one session be shared amongst multiple threads? In the book Drools JBoss
Rules 5.0 Developer's Guide it says that sessions cannot be shared as they
contain state which i understand but in chapter 12 they say that "Drools
supports parallel execution mode. One session can be executed by multiple
threads." using Knowledge partitioning what exactly does this mean? Thanks
in advance.
Kind regards,
James.
16 years, 2 months
Drools Fusion Performance and RETE algorithm
by Orlando Ricardo Da Silva Costa
Hi all
Looking at "Drools JBoss Rules 5 0 Developer's guide" it addresses the
Fusion component at page 134, stating:
"This problem cannot be solved by the standard Drools rule engine. The
volume of events is huge and it happens asynchronously. If we simply
inserted them into the knowledge session, we would soon run out of
memory. While the Rete algorithm behind Drools doesn't have any
theoretical limitation on number of objects in the session, we could
use the processing power more wisely. Drools Fusion is the right
candidate for this kind of task."
Ok, but my question is if this is enough, because I would guess that
Fusion could be used to derived a more complex/rich event from the
stream of events, and afterwards that complex event would be inserted
in Working Memory (but not the flow of events that have generated the
more complex event), thus reducing RETE algorithm processing. But
since in our case every event will most certainly fire a rule, I am
not sure about Fusion's usage.
This is because our project is more a kind of
Event-Trigger-Rule/Action system, meaning we have a high volume of
incoming events (say more than 5000/minute), but each of the events
will have to trigger a rule (and usually a rule is more or less a
complex action, invoking DB operations and data structures
manipulation).
So, by using Fusion entry-points, would that be different than just
sending the events as "normal" facts to Working Memory, or by dividing
this in entry-points( or so called streams) we would have benefits in
the RETE processing (I am assuming Fusion also uses RETE someway)?
Best regards
Orlando.
PS-Does anyone know where can I find more info on the coupling of
Drools Expert and Fusion?
16 years, 2 months
Drools Scalability
by Orlando Costa
Hi all
I have been looking at Drools (Expert, Fusion and Flow) to see how
feasible it is to use it in our project. We have requirements for
scalability:
1) system must be vertically scalable
2) system must be horizontally scalable
I guess for 1), we could use KnowledgeBase partitioning, but for 2) I
have no idea...has someone been looking at this, does it make sense to
have a rule engine horizontally scalable at all?
Br
Orlando.
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16 years, 2 months
