[rules-users] To know about correct Drools rule file (drl) syntaxes

[Hareendra Pelige]

Hi All,

I am new to this Drools rule engine. After looking at its features, I am
really interested on this. I tried few samples given in jboss site and
got to know high-level understanding of the rule engine and how it can
be used in our business applications.

But, I am really confused with the rule syntaxes used in sample files,
samples published in the internet.

 

Few such syntaxes are listed bellow. Could you please let me know which
is better for enterprise applications?

 

1. 

rule "Hello World"

    dialect "mvel"

            when

                        m : Message( status == Message.HELLO, message :
message

)

            then

                System.out.println( message ); 

                modify ( m ) { message = "Goodbyte cruel world",

                               status = Message.GOODBYE };

                System.out.println( message );


end

 

rule "Good Bye"

    dialect "java"

            when

                        Message( status == Message.GOODBYE, message :
message )

            then

                        System.out.println( message );                

End

 

Questions:

Here, what is "dialect" and what are 'mvel' and 'java'?

What are the differences between 'mvel' and 'java'

 

2.

<rule-set name="disposition rules"

    xmlns="http://drools.org/rules"    

    xmlns:java="http://drools.org/semantics/java"

    xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"

    xs:schemaLocation="http://drools.org/rules rules.xsd

 
http://drools.org/semantics/java java.xsd">

  

            <!-- season sale means 10% off item price -->

    <rule name="season sales">

        <parameter identifier="item">

            <class>de.linsin.example.drools.domain.Item</class>

        </parameter>

        <parameter identifier="bill">

            <class>de.linsin.example.drools.domain.Bill</class>

        </parameter>

        <parameter identifier="quantity">

            <class>java.lang.Integer</class>

        </parameter>

        <java:condition>

            item.isOnSeasonSale() == true

        </java:condition>

        <java:consequence>

            double price = (item.getPrice()*(100-10))/100;

            bill.addItem(item, quantity.intValue()*price);

        </java:consequence>

    </rule>

    

    <!-- customer discount means 5% off total -->

    <rule name="discount">

        <parameter identifier="bill">

            <class>de.linsin.example.drools.domain.Bill</class>

        </parameter>

        <parameter identifier="customer">

            <class>de.linsin.example.drools.domain.Customer</class>

        </parameter>

        <java:condition>

            customer.isDiscount() == true

        </java:condition>

        <java:consequence>

            double total = bill.getTotal();

            bill.setTotal((total*(100-5))/100);

        </java:consequence>

    </rule>

</rule-set>

 

3. 

package com.test

 

import com.test.common.*;

import java.util.ArrayList;

 

// Extract TestData

rule "Extract Test Data"

            dialect "java"

            when

                        $productRequest :
ProductRequest(bookingRequest!=null) 

            then

                        insert( $productRequest.getDivision() );

 

                        System.out.println( "Extracted Test Data."); end

 

 

 

Could you please point me a location(s) to learn drl rule language with
its syntaxes?

 

Appreciate any of your help.

 

Thanks and regards

Hareendra Pelige

 

 

-----Original Message-----
From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Benjamin J
McMillan
Sent: Thursday, May 29, 2008 3:15 AM
To: Rules Users List
Subject: [rules-users] the BRMS and queries

 

All,

 

Either the BRMS, when uploading a DRL file, doesn't read in queries, or

it doesn't build them into the deployment package.

 

Is this by design, or a bug? For now my application (my unit tests,

actually) queries the working memory for decision objects, instead of

having rules respond to the decisions and put them into a data structure

the java app can see. I could do the latter, but I'm just wondering if

maybe I'm doing something wrong regarding queries and the BRMS.

 

Thanks!

 

Ben

 

 

 

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