CEP functionality
by David Boaz
Dear all,
We posted this question two weeks ago, but with no replies. please forgive
me for posting it again.
In our business, most of the facts have time-stamp attributes. For example,
each laboratory test (a fact) has the time stamp when the sample was taken,
and when the machine produced the result value. In our business-logic, we
often analyze the relation between facts using these attributes.
For example:
1) finding two adjacent labResults with an increasing value
2) checking whether 3 facts are consecutive
3) counting the number of facts fulfilling a specific constraint within a
specific time window.
We were happy to read (in the blog) about the new CEP feature which is about
to be added to drools 5.0.
* Where can we find a more detailed description of CEP functionality in
drools?
* Is it a good idea to use CEP for analyzing historic data (retrieved from
the database)? or is it best for online data.
* Can we use CEP in a stateless session?
* As we understand, CEP attaches to each fact a temporal attribute of the
assertion time. Can we define that a particular attribute (e.g.,
LabResult.samplingDate) will be used as the time stamp? Or, should we assert
the facts by their temporal order, and advance the session-clock
appropriately?
* Can we use CEP to analyze the data in the examples above?
Many thanks for the help, David
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17 years, 2 months
Stateless session and rule flows
by Yoni Mazar
Hi Guys,
We are trying to work with drools with stateless session (Sequential) and to
apply rule flows.
we use the following code:
//define diagnosis and patient here
...
StatelessSession session = ruleBase.newStatelessSession();
//Here we would like to use: session.startProcess("ruleflow id") but this is
a method which belongs to
//StatefullSession only.
session.execute(new Object[] {diagnosis, patient});
How can we do that in steteless mode?
Thanks,
Yoni
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17 years, 2 months
NullPointerException for Integer null
by techy
Hello,
For following rule, NullPointerException is thrown for null id in 4.x. is
this expected? Please clarify.
Foo{
Integer id;
}
Rule "null check"
foo : Foo(id==null)
then
end
stack trace:
java.lang.NullPointerException
at
org.drools.base.extractors.BaseObjectClassFieldExtractor.getIntValue(BaseObjectClassFieldExtractor.java:95)
at
org.drools.base.ClassFieldExtractor.getIntValue(ClassFieldExtractor.java:197)
at
org.drools.base.evaluators.IntegerFactory$IntegerLessEvaluator.evaluate(IntegerFactory.java:241)
at
org.drools.rule.VariableRestriction.isAllowed(VariableRestriction.java:73)
at org.drools.rule.VariableConstraint.isAllowed(VariableConstraint.java:67)
at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:137)
at
org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:318)
at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:162)
at org.drools.reteoo.Rete.assertObject(Rete.java:175)
at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
at
org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:71)
at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:911)
at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:883)
at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:684)
at
org.drools.reteoo.ReteooStatelessSession.execute(ReteooStatelessSession.java:160)
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17 years, 2 months
need some advice in defining rules
by Brody bach
Hi all,
I'm having difficulty in defining a rule for the following problem:
We need to check if within a week there are more than 5 objects of type
Reminder inserted into Memory.
(one day corresponds to one object)
The number of the inserted objects depends on the usage of the application.
That means there could be nothing, 1, 2, or any number of the objects.
Before, within a session, I inserted a list containg data from within one
week (7 days).
Than I can check using the rule:
when:
$list : list(size > 5)
Reminder() from $list
no String(trim == "limit reached");
then
System.out.println("This rule fires");
insert new String("limit reached");
Now I need to insert a list containing data from a whole month, but I still
need to check whether within one week there are more than 5 reminders exist.
so, the constraint list> 5 can't be used anymore for a single list. I tried
to break the whole list in several smaller list, where each list represents
one week.
Now the problem is, if the rule fires for a certain week, than it won't work
for the following weeks anymore.
My idea is then to insert an integer containing specific number to the
current list, i.e. the calendar week (i.e insert new Integer(52)) and then
to prove this in LHS; but the problem is now how to prove the week number in
LHS? as I remeber, a function can only be called within an eval statement
and in this case actually I should only prove the existence of an Integer
Hope my explanation is quite understandable and looking forward for any
hints
Regards
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17 years, 2 months
problem escaping quote in eval
by samlotti
Hello,
I'm trying to construct a rule in drool V4 that contains and eval and a
literal string that may contain quotes. I've tried escaping the quote but
get the error below. The \" works outside an eval.
rule "evalList2"
when
Var( eval( "tt".equals("t\"t")))
then
System.out.println( "evalList2" );
end
Error:
java.lang.NullPointerException:
at
org.drools.rule.PredicateConstraint.createContextEntry(PredicateConstraint.java:201)
at org.drools.reteoo.AlphaNode.createMemory(AlphaNode.java:230)
...
It looks like a change was made to V3 to fix this but doesnt appear to work
in V4, does anyone know how to construct this type of rule?
Thanks
Sam
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17 years, 2 months
Drools 4.0.7 - Rules not fired
by Benoit VILLAUMIE
Hello,
I am using Drools engine 4.0.7 and Eclipse 3.3 drools plugin.
I have a very basic/dumb problem but I do not understand where my error is :
I have 2 rules
---------------------------------
package poc
import poc.FlashFact;
*rule "HP one"*
when
FlashFact( homepage == "one");
then
System.out.println("*** HP one");
end
*rule "HP commons"*
when
FlashFact();
then
System.out.println("*** HP commons ");
end
----------------------------------
I insert a FlashFact which homepage is set with "one" value.
In my understanding, both rules "HP one" and "HP commons" should be
fired. Instead, only "HP commons" is launched. I have compared with the
Drools State example (which works fine), but I do not notice nothing.
Thanks for your help.
The code of the FlashFact class
---------------------------------
package poc;
public class FlashFact {
public FlashFact() {
this(null);
}
public FlashFact(String homepage) {
this.setHomepage(homepage);
}
private String homepage;
/**
* @return the homepage
*/
public final String getHomepage() {
return this.homepage;
}
/**
* @param homepage the homepage to set
*/
public final void setHomepage(String homepage) {
this.homepage = homepage;
}
}
---------------------------------
The code of the launcher
---------------------------------
package poc;
import java.io.InputStreamReader;
import org.drools.RuleBase;
import org.drools.RuleBaseFactory;
import org.drools.StatefulSession;
import org.drools.audit.WorkingMemoryFileLogger;
import org.drools.compiler.PackageBuilder;
public class FlashUndeployedRulesMain {
public static void main(String[] args) throws Exception {
StatefulSession session = null;
WorkingMemoryFileLogger logger = null;
try {
PackageBuilder builder = new PackageBuilder();
builder.addPackageFromDrl(new InputStreamReader(
FlashUndeployedRulesMain.class.getClassLoader()
.getResourceAsStream(RULE)));
final RuleBase ruleBase = RuleBaseFactory.newRuleBase();
ruleBase.addPackage(builder.getPackage());
session = ruleBase.newStatefulSession();
logger = new WorkingMemoryFileLogger(
session);
logger.setFileName("log/flash");
// inserting facts
FlashFact HPFrance = new FlashFact("one");
session.insert(HPFrance);
session.fireAllRules();
} finally {
if(session != null) {session.dispose();}
if(logger != null) {logger.writeToDisk();}
}
}
private static final String RULE = "poc/Flash.drl";
---------------------------------
17 years, 2 months
using matches in a collection
by ygaurav
Hi All
i am new to drools and I am hoping that some body can help me out here.
I data in string array and I would like to check if one of the entry starts
with the string I have. How can check it ?
Code is shown below
@java
class ABC {
String[] array = new String[]{"abcdef","ghijkl","mnopqrst"}
}
@drools
rule "check something"
when
$abc : ( ABC.array contains a single entry which start with "abc" )
Is there a way I can do it ? If it is not possible what is way I can achive
it
Thanks
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17 years, 2 months
KnowledgeBase threadsafe?
by Dan Seaver
I'm using various KnowledgeBase objects in a J2EE environment, using JBoss
4.2 as the application server. Currently, I keep a list of KnowledgeBase
objects in a stateless session bean. The thought being that to keep the
application scalable, we don't want contention around rule sessions.
However, I just heard that KnowledgeBase is thread safe. This would mean
that I could instantiate a KnowledgeBase once and have multiple
StatelessKnowledgeSessions using it concurrently.
Can anyone verify that KnowledgeBase is thread safe for me?
Would this technique potentially cause contention on a busy system?
Dan
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17 years, 2 months
