conways game of life
by Mark Proctor
For anyone looking for a good and complex example on how to write rules
properly, please look at Conways Game of Life in drools-examples, for
extra bonus points compare it to the old version in M1. You'll see
nearly all the logic is moved from java to the drl and we have removed
the need for nested objects by using objects relaitionally, which also
allows us to exploit cross products to drive the application.
Mark
3 months, 1 week
java.lang.OutOfMemoryError: Java heap space
by vdelbart
Hello,
In my tests of the 4.0.3, I have some : java.lang.OutOfMemoryError.
So, I try a simple test with 10.000 sequential execution of 1 rule with no
context and just a workingmemorylogger and I have the error :
java.lang.OutOfMemoryError: Java heap space
My code is :
public class ExecReglesMemotyTest
{
private static final Reader DRL = new
InputStreamReader(ExecReglesMemotyTest.class
.getResourceAsStream("/rules/exemple.drl"));
private static final String FICHIER_LOG = "session";
/**
* @param args
*/
public static void main(String[] args)
{
try
{
PackageBuilder builder = new PackageBuilder();
builder.addPackageFromDrl(DRL);
RuleBase ruleBase = RuleBaseFactory.newRuleBase();
ruleBase.addPackage(builder.getPackage());
for (int i = 0; i < 10000; i++)
{
StatefulSession session = ruleBase.newStatefulSession();
WorkingMemoryFileLogger logger = new WorkingMemoryFileLogger(session);
logger.setFileName(FICHIER_LOG);
session.fireAllRules();
logger.writeToDisk();
session.dispose();
}
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
with this rule (doesn't matter):
#created on: Fri Nov 09 15:48:45 CET 2007
package initPackage
#list any import classes here.
rule "ERG9"
when
then
end
I try this in 4.0.1, and it's working (no OutOfMemoryError)
What's the problem ?
thanks for any information,
V.
--
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13 years, 2 months
Log4j in the rules?
by granz＠MIT.EDU
Hi,
Is it possible to use Log4j inside the rules (RHS)?? (drl file)
Thanks,
Fabrice
14 years, 3 months
About for and inheritance
by Chris Woodrow
Hi,
I recently find out a few issues using for, and I wanted to share it with
you. I made a simple exemple to illustrate my purpose.
My classes are (I did not represent accessors & constructors):
public class Cheese {
protected String name;
}
public class FrenchCheese extends Cheese{
private String smell;
}
public class Person {
private Cheese likes;
}
Here is my rule set :
package rules
rule "likes cheese"
when
$person : Person ()
Cheese( ) from $person.getLikes()
then
System.out.println("likes cheese");
end
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
First test :
Cheese cheese = new FrenchCheese("good", "camembert");
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
Wich is expected...
Second test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
That's the first strange thing. As far as I am concerned, rule "likes french
cheese" should not match (since a Cheese is not a FrenchCheese).
I made a change to the second rule :
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( smell == "good" ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
Third test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
output :
It throwed an exception : Exception in thread "main"
java.lang.ClassCastException: rules.Cheese
I am not saying the ClassCastException is not to expect in such a case but I
think I would simply expect it not to match (as far as a Cheese is not a
FrenchCheese).
Chris
14 years, 12 months
Drools 4.0, Support for multiple pattern in accumulate source pattern
by Juergen
It appears as if accumulate does support only a single pattern CE as
source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price
),
sum( price )
)
Is it possible to have more than one pattern in the source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price,
type : type
)
Person(
favouriteCheese == type,
age > 30
),
sum( price )
)
The same could be said for collect, but there the problem to specify
which item of a matching tuple is to be collected, but this could be
handled recreating collect via accumulate, e.g.:
Collection() from accumulate(
cheese : Cheese(
type : type
)
Person(
favouriteCheese == type,
age > 30
),
collect( cheese )
)
15 years
JBoss Rules as a Daemon Service
by Arjun Dhar
Hi,
I uploaded the JBoss Rules 4 WAR; I saw the repository options but no admin
console to run a service. Maybe I'm missing something?!?!
Q) Being under the cover of the JBoss server am sure there must be some
fascility to run this as a daemon service 'out of the box'! Right?? <--
Important
(posted this 3 days ago but it got lost somwhere; prob deleted the approval
mail; FYI not being impatient :o) but its important so would like to know)
Thanks!
16 years, 9 months
Localization in DSL
by Shigeaki Wakizaka
Hello.
I'd like to use Japanese in DSL.
Is it possible?
Do you have a plan to do the localize-thing with DSL and
brand-new BRMS?
Thanks in advance
Shige
16 years, 10 months
how to specify classpath dependencies in .drl files.
by Godmar Back
My question is how to manage a rule base that is composed from sets of
rules drawn from different sources.
Our goal is to supply sets of rules as .jar files - each .jar file
containing a related set of rules. For instance, consider an expert
system where different experts could export their expertise in such a
jar file. Such a .jar file would contain one or more .drl files and a
set of supporting .java classes. We'd like to be able to refer to
these .jar files using a URLClassLoader and/or JarURLConnection so
they can be referred to without a user having to download them prior
to starting their application.
Users should be able to combine those provided rules (that is, the
rules of those experts whose knowledge they wish to exploit) with
their own rules in their own .drl files.
My question is whether drools supports such a setup easily.
Specifically, is there a way for a user to import external .jar files
in their .drl files? A statement such as
use jar:http://expertbase.com/expert1/knowledge5.jar
which would instruct the rule compiler to load the classes from this
jar to its compile class path, and which would instruct the class
loader used to load the user's classes to delegate to the loader used
to load the jar file's classes? [Note that a given expert's knowledge
should only be loaded by one classloader.]
I browsed through the API and discovered that the package builder
configuration allows the specification of a class loader. Does this
mean the rule compiler will attempt to load related classes through
this loader as well? If so, it would need to use reflection to examine
those classes (which I'd find unlikely). If not, is there a way to
control the rule compiler's compiler classpath?
In our current prototype, we need to load everything through the
application classpath to avoid compile errors.
- Godmar
16 years, 12 months
Independent rule evaluations
by Yuri
Considering that I have a set of rules that can be time consuming to assert is
there a way to separate them from other rules without having to resort to
multiple working memories?
I basically want to be able to assert facts and evalute a set of rules as fast
as I can before actually having the time consuming set of rules evaluate.
thanks,
17 years, 2 months
Writing rules using java..
by Kolla, Sandeep
Hi Rahul,
Its not about storing the whole file into the database.
I would have a Table representing the parameteres required to construct
a rule.
For example.
Tables:
RuleSetTable:
Ruleset_id
Ruleset_name
RuleTable:
Rule_id
Rule_name
Rule_saliance
Rule_condition
Rule_consequence
Ruleset_id
Now while loading the rules the application basically should read from
the DB, and construct the rules, as everything required to construct the
rules is avaliable in the tables.
This requirement had come up because as the rules keep changing quite
frequently, we don't want to bring down the application to load a new
DRL file.
Hope you understood what I want to achieve.
Thanks much,
Sandeep.
17 years, 3 months
