Designing a decision service using guided rules

Procedure

1. In Business Central, go to Menu → Design → Projects and click the project name.
2. Click Add Asset → Guided Rule.

3. Enter an informative Guided Rule name and select the appropriate Package. The package that you specify must be the same package where the required data objects have been assigned or will be assigned.

   You can also select Show declared DSL sentences if any domain specific language (DSL) assets have been defined in your project. These DSL assets will then become usable objects for conditions and actions that you define in the guided rules designer.

4. Click Ok to create the rule asset.

   The new guided rule is now listed in the Guided Rules panel of the Project Explorer, or in the Guided Rules (with DSL) panel if you selected the Show declared DSL sentences option.

5. Click the Data Objects tab and confirm that all data objects required for your rules are listed. If not, click New item to import data objects from other packages, or create data objects within your package.

6. After all data objects are in place, return to the Model tab of the guided rules designer and use the buttons on the right side of the window to add and define the WHEN (condition) and THEN (action) sections of the rule, based on the available data objects.

   Figure 4.1. The guided rules designer

   

   The WHEN part of the rule contains the conditions that must be met to execute an action. For example, if a bank requires loan applicants to have over 21 years of age, then the WHEN condition of an Underage rule would be Age | less than | 21.

   The THEN part of the rule contains the actions to be performed when the conditional part of the rule has been met. For example, when the loan applicant is under 21 years old, the THEN action would set approved to false, declining the loan because the applicant is under age.

   You can also specify exceptions for more complex rules, such as if a bank may approve of an under-aged applicant when a guarantor is involved. In that case, you would create or import a guarantor data object and then add the field to the guided rule.

7. After you define all components of the rule, click Validate in the upper-right toolbar of the guided rules designer to validate the guided rule. If the rule validation fails, address any problems described in the error message, review all components in the rule, and try again to validate the rule until the rule passes.
8. Click Save in the guided rules designer to save your work.

Procedure

1. In Business Central, go to Menu → Design → Projects and click the project name.

2. In the upper-right corner of the project Assets page, click Deploy to build the project and deploy it to KIE Server. If the build fails, address any problems described in the Alerts panel at the bottom of the screen.

   For more information about project deployment options, see Packaging and deploying a Red Hat Decision Manager project.

   Note

   If the rule assets in your project are not built from an executable rule model by default, verify that the following dependency is in the pom.xml file of your project and rebuild the project:

   <dependency>
     <groupId>org.drools</groupId>
     <artifactId>drools-model-compiler</artifactId>
     <version>${rhdm.version}</version>
   </dependency>

   This dependency is required for rule assets in Red Hat Decision Manager to be built from executable rule models by default. This dependency is included as part of the Red Hat Decision Manager core packaging, but depending on your Red Hat Decision Manager upgrade history, you may need to manually add this dependency to enable the executable rule model behavior.

   For more information about executable rule models, see Packaging and deploying a Red Hat Decision Manager project.

3. Create a Maven or Java project outside of Business Central, if not created already, that you can use for executing rules locally or that you can use as a client application for executing rules on KIE Server. The project must contain a pom.xml file and any other required components for executing the project resources.

   For example test projects, see "Other methods for creating and executing DRL rules".

4. Open the pom.xml file of your test project or client application and add the following dependencies, if not added already:

   • kie-ci: Enables your client application to load Business Central project data locally using ReleaseId
   • kie-server-client: Enables your client application to interact remotely with assets on KIE Server
   • slf4j: (Optional) Enables your client application to use Simple Logging Facade for Java (SLF4J) to return debug logging information after you interact with KIE Server

   Example dependencies for Red Hat Decision Manager 7.8 in a client application pom.xml file:

   <!-- For local execution -->
   <dependency>
     <groupId>org.kie</groupId>
     <artifactId>kie-ci</artifactId>
     <version>7.39.0.Final-redhat-00005</version>
   </dependency>
   
   <!-- For remote execution on KIE Server -->
   <dependency>
     <groupId>org.kie.server</groupId>
     <artifactId>kie-server-client</artifactId>
     <version>7.39.0.Final-redhat-00005</version>
   </dependency>
   
   <!-- For debug logging (optional) -->
   <dependency>
     <groupId>org.slf4j</groupId>
     <artifactId>slf4j-simple</artifactId>
     <version>1.7.25</version>
   </dependency>

   For available versions of these artifacts, search the group ID and artifact ID in the Nexus Repository Manager online.

   Note

   Instead of specifying a Red Hat Decision Manager <version> for individual dependencies, consider adding the Red Hat Business Automation bill of materials (BOM) dependency to your project pom.xml file. The Red Hat Business Automation BOM applies to both Red Hat Decision Manager and Red Hat Process Automation Manager. When you add the BOM files, the correct versions of transitive dependencies from the provided Maven repositories are included in the project.

   Example BOM dependency:

   <dependency>
     <groupId>com.redhat.ba</groupId>
     <artifactId>ba-platform-bom</artifactId>
     <version>7.8.0.redhat-00005</version>
     <scope>import</scope>
     <type>pom</type>
   </dependency>

   For more information about the Red Hat Business Automation BOM, see What is the mapping between Red Hat Decision Manager and the Maven library version?.

5. Ensure that the dependencies for artifacts containing model classes are defined in the client application pom.xml file exactly as they appear in the pom.xml file of the deployed project. If dependencies for model classes differ between the client application and your projects, execution errors can occur.

   To access the project pom.xml file in Business Central, select any existing asset in the project and then in the Project Explorer menu on the left side of the screen, click the Customize View gear icon and select Repository View → pom.xml.

   For example, the following Person class dependency appears in both the client and deployed project pom.xml files:

   <dependency>
     <groupId>com.sample</groupId>
     <artifactId>Person</artifactId>
     <version>1.0.0</version>
   </dependency>

6. If you added the slf4j dependency to the client application pom.xml file for debug logging, create a simplelogger.properties file on the relevant classpath (for example, in src/main/resources/META-INF in Maven) with the following content:

   org.slf4j.simpleLogger.defaultLogLevel=debug

7. In your client application, create a .java main class containing the necessary imports and a main() method to load the KIE base, insert facts, and execute the rules.

   For example, a Person object in a project contains getter and setter methods to set and retrieve the first name, last name, hourly rate, and the wage of a person. The following Wage rule in a project calculates the wage and hourly rate values and displays a message based on the result:

   package com.sample;
   
   import com.sample.Person;
   
   dialect "java"
   
   rule "Wage"
     when
       Person(hourlyRate * wage > 100)
       Person(name : firstName, surname : lastName)
     then
       System.out.println("Hello" + " " + name + " " + surname + "!");
       System.out.println("You are rich!");
   end

   To test this rule locally outside of KIE Server (if needed), configure the .java class to import KIE services, a KIE container, and a KIE session, and then use the main() method to fire all rules against a defined fact model:

   Executing rules locally

   import org.kie.api.KieServices;
   import org.kie.api.builder.ReleaseId;
   import org.kie.api.runtime.KieContainer;
   import org.kie.api.runtime.KieSession;
   import org.drools.compiler.kproject.ReleaseIdImpl;
   
   public class RulesTest {
   
     public static final void main(String[] args) {
       try {
         // Identify the project in the local repository:
         ReleaseId rid = new ReleaseIdImpl("com.myspace", "MyProject", "1.0.0");
   
         // Load the KIE base:
         KieServices ks = KieServices.Factory.get();
         KieContainer kContainer = ks.newKieContainer(rid);
         KieSession kSession = kContainer.newKieSession();
   
         // Set up the fact model:
         Person p = new Person();
         p.setWage(12);
         p.setFirstName("Tom");
         p.setLastName("Summers");
         p.setHourlyRate(10);
   
         // Insert the person into the session:
         kSession.insert(p);
   
         // Fire all rules:
         kSession.fireAllRules();
         kSession.dispose();
       }
   
       catch (Throwable t) {
         t.printStackTrace();
       }
     }
   }

   To test this rule on KIE Server, configure the .java class with the imports and rule execution information similarly to the local example, and additionally specify KIE services configuration and KIE services client details:

   Executing rules on KIE Server

   package com.sample;
   
   import java.util.ArrayList;
   import java.util.HashSet;
   import java.util.List;
   import java.util.Set;
   
   import org.kie.api.command.BatchExecutionCommand;
   import org.kie.api.command.Command;
   import org.kie.api.KieServices;
   import org.kie.api.runtime.ExecutionResults;
   import org.kie.api.runtime.KieContainer;
   import org.kie.api.runtime.KieSession;
   import org.kie.server.api.marshalling.MarshallingFormat;
   import org.kie.server.api.model.ServiceResponse;
   import org.kie.server.client.KieServicesClient;
   import org.kie.server.client.KieServicesConfiguration;
   import org.kie.server.client.KieServicesFactory;
   import org.kie.server.client.RuleServicesClient;
   
   import com.sample.Person;
   
   public class RulesTest {
   
     private static final String containerName = "testProject";
     private static final String sessionName = "myStatelessSession";
   
     public static final void main(String[] args) {
       try {
         // Define KIE services configuration and client:
         Set<Class<?>> allClasses = new HashSet<Class<?>>();
         allClasses.add(Person.class);
         String serverUrl = "http://$HOST:$PORT/kie-server/services/rest/server";
         String username = "$USERNAME";
         String password = "$PASSWORD";
         KieServicesConfiguration config =
           KieServicesFactory.newRestConfiguration(serverUrl,
                                                   username,
                                                   password);
         config.setMarshallingFormat(MarshallingFormat.JAXB);
         config.addExtraClasses(allClasses);
         KieServicesClient kieServicesClient =
           KieServicesFactory.newKieServicesClient(config);
   
         // Set up the fact model:
         Person p = new Person();
         p.setWage(12);
         p.setFirstName("Tom");
         p.setLastName("Summers");
         p.setHourlyRate(10);
   
         // Insert Person into the session:
         KieCommands kieCommands = KieServices.Factory.get().getCommands();
         List<Command> commandList = new ArrayList<Command>();
         commandList.add(kieCommands.newInsert(p, "personReturnId"));
   
         // Fire all rules:
         commandList.add(kieCommands.newFireAllRules("numberOfFiredRules"));
         BatchExecutionCommand batch = kieCommands.newBatchExecution(commandList, sessionName);
   
         // Use rule services client to send request:
         RuleServicesClient ruleClient = kieServicesClient.getServicesClient(RuleServicesClient.class);
         ServiceResponse<ExecutionResults> executeResponse = ruleClient.executeCommandsWithResults(containerName, batch);
         System.out.println("number of fired rules:" + executeResponse.getResult().getValue("numberOfFiredRules"));
       }
   
       catch (Throwable t) {
         t.printStackTrace();
       }
     }
   }

8. Run the configured .java class from your project directory. You can run the file in your development platform (such as Red Hat CodeReady Studio) or in the command line.

   Example Maven execution (within project directory):

   mvn clean install exec:java -Dexec.mainClass="com.sample.app.RulesTest"

   Example Java execution (within project directory)

   javac -classpath "./$DEPENDENCIES/*:." RulesTest.java
   java -classpath "./$DEPENDENCIES/*:." RulesTest

9. Review the rule execution status in the command line and in the server log. If any rules do not execute as expected, review the configured rules in the project and the main class configuration to validate the data provided.