Chapter 21. Example decisions in Red Hat Decision Manager for an IDE Red Hat Decision Manager provides example decisions distributed as Java classes that you can import into your integrated development environment (IDE). You can use these examples to better understand decision engine capabilities or use them as a reference for the decisions that you define in your own Red Hat Decision Manager projects. The following example decision sets are some of the examples available in Red Hat Decision Manager: Hello World example : Demonstrates basic rule execution and use of debug output State example : Demonstrates forward chaining and conflict resolution through rule salience and agenda groups Fibonacci example : Demonstrates recursion and conflict resolution through rule salience Banking example : Demonstrates pattern matching, basic sorting, and calculation Pet Store example : Demonstrates rule agenda groups, global variables, callbacks, and GUI integration Sudoku example : Demonstrates complex pattern matching, problem solving, callbacks, and GUI integration House of Doom example : Demonstrates backward chaining and recursion Note For optimization examples provided with Red Hat build of OptaPlanner, see Getting started with Red Hat build of OptaPlanner . 21.1. Importing and executing Red Hat Decision Manager example decisions in an IDE You can import Red Hat Decision Manager example decisions into your integrated development environment (IDE) and execute them to explore how the rules and code function. You can use these examples to better understand decision engine capabilities or use them as a reference for the decisions that you define in your own Red Hat Decision Manager projects. Prerequisites Java 8 or later is installed. Maven 3.5.x or later is installed. An IDE is installed, such as Red Hat CodeReady Studio. Procedure Download and unzip the Red Hat Process Automation Manager 7.13.5 Source Distribution from the Red Hat Customer Portal to a temporary directory, such as /rhpam-7.13.5-sources . Open your IDE and select File Import Maven Existing Maven Projects , or the equivalent option for importing a Maven project. Click Browse , navigate to ~/rhpam-7.13.5-sources/src/drools-USDVERSION/drools-examples (or, for the Conway's Game of Life example, ~/rhpam-7.13.5-sources/src/droolsjbpm-integration-USDVERSION/droolsjbpm-integration-examples ), and import the project. Navigate to the example package that you want to run and find the Java class with the main method. Right-click the Java class and select Run As Java Application to run the example. To run all examples through a basic user interface, run the DroolsExamplesApp.java class (or, for Conway's Game of Life, the DroolsJbpmIntegrationExamplesApp.java class) in the org.drools.examples main class. Figure 21.1. Interface for all examples in drools-examples (DroolsExamplesApp.java) Figure 21.2. Interface for all examples in droolsjbpm-integration-examples (DroolsJbpmIntegrationExamplesApp.java) 21.2. Hello World example decisions (basic rules and debugging) The Hello World example decision set demonstrates how to insert objects into the decision engine working memory, how to match the objects using rules, and how to configure logging to trace the internal activity of the decision engine. The following is an overview of the Hello World example: Name : helloworld Main class : org.drools.examples.helloworld.HelloWorldExample (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.helloworld.HelloWorld.drl (in src/main/resources ) Objective : Demonstrates basic rule execution and use of debug output In the Hello World example, a KIE session is generated to enable rule execution. All rules require a KIE session for execution. KIE session for rule execution KieServices ks = KieServices.Factory.get(); 1 KieContainer kc = ks.getKieClasspathContainer(); 2 KieSession ksession = kc.newKieSession("HelloWorldKS"); 3 1 Obtains the KieServices factory. This is the main interface that applications use to interact with the decision engine. 2 Creates a KieContainer from the project class path. This detects a /META-INF/kmodule.xml file from which it configures and instantiates a KieContainer with a KieModule . 3 Creates a KieSession based on the "HelloWorldKS" KIE session configuration defined in the /META-INF/kmodule.xml file. Note For more information about Red Hat Decision Manager project packaging, see Packaging and deploying an Red Hat Decision Manager project . Red Hat Decision Manager has an event model that exposes internal engine activity. Two default debug listeners, DebugAgendaEventListener and DebugRuleRuntimeEventListener , print debug event information to the System.err output. The KieRuntimeLogger provides execution auditing, the result of which you can view in a graphical viewer. Debug listeners and audit loggers // Set up listeners. ksession.addEventListener( new DebugAgendaEventListener() ); ksession.addEventListener( new DebugRuleRuntimeEventListener() ); // Set up a file-based audit logger. KieRuntimeLogger logger = KieServices.get().getLoggers().newFileLogger( ksession, "./target/helloworld" ); // Set up a ThreadedFileLogger so that the audit view reflects events while debugging. KieRuntimeLogger logger = ks.getLoggers().newThreadedFileLogger( ksession, "./target/helloworld", 1000 ); The logger is a specialized implementation built on the Agenda and RuleRuntime listeners. When the decision engine has finished executing, logger.close() is called. The example creates a single Message object with the message "Hello World" , inserts the status HELLO into the KieSession , executes rules with fireAllRules() . Data insertion and execution // Insert facts into the KIE session. final Message message = new Message(); message.setMessage( "Hello World" ); message.setStatus( Message.HELLO ); ksession.insert( message ); // Fire the rules. ksession.fireAllRules(); Rule execution uses a data model to pass data as inputs and outputs to the KieSession . The data model in this example has two fields: the message , which is a String , and the status , which can be HELLO or GOODBYE . Data model class public static class Message { public static final int HELLO = 0; public static final int GOODBYE = 1; private String message; private int status; ... } The two rules are located in the file src/main/resources/org/drools/examples/helloworld/HelloWorld.drl . The when condition of the "Hello World" rule states that the rule is activated for each Message object inserted into the KIE session that has the status Message.HELLO . Additionally, two variable bindings are created: the variable message is bound to the message attribute and the variable m is bound to the matched Message object itself. The then action of the rule specifies to print the content of the bound variable message to System.out , and then changes the values of the message and status attributes of the Message object bound to m . The rule uses the modify statement to apply a block of assignments in one statement and to notify the decision engine of the changes at the end of the block. "Hello World" rule The "Good Bye" rule is similar to the "Hello World" rule except that it matches Message objects that have the status Message.GOODBYE . "Good Bye" rule To execute the example, run the org.drools.examples.helloworld.HelloWorldExample class as a Java application in your IDE. The rule writes to System.out , the debug listener writes to System.err , and the audit logger creates a log file in target/helloworld.log . System.out output in the IDE console System.err output in the IDE console To better understand the execution flow of this example, you can load the audit log file from target/helloworld.log into your IDE debug view or Audit View , if available (for example, in Window Show View in some IDEs). In this example, the Audit view shows that the object is inserted, which creates an activation for the "Hello World" rule. The activation is then executed, which updates the Message object and causes the "Good Bye" rule to activate. Finally, the "Good Bye" rule is executed. When you select an event in the Audit View , the origin event, which is the "Activation created" event in this example, is highlighted in green. Figure 21.3. Hello World example Audit View 21.3. State example decisions (forward chaining and conflict resolution) The State example decision set demonstrates how the decision engine uses forward chaining and any changes to facts in the working memory to resolve execution conflicts for rules in a sequence. The example focuses on resolving conflicts through salience values or through agenda groups that you can define in rules. The following is an overview of the State example: Name : state Main classes : org.drools.examples.state.StateExampleUsingSalience , org.drools.examples.state.StateExampleUsingAgendaGroup (in src/main/java ) Module : drools-examples Type : Java application Rule files : org.drools.examples.state.*.drl (in src/main/resources ) Objective : Demonstrates forward chaining and conflict resolution through rule salience and agenda groups A forward-chaining rule system is a data-driven system that starts with a fact in the working memory of the decision engine and reacts to changes to that fact. When objects are inserted into working memory, any rule conditions that become true as a result of the change are scheduled for execution by the agenda. In contrast, a backward-chaining rule system is a goal-driven system that starts with a conclusion that the decision engine attempts to satisfy, often using recursion. If the system cannot reach the conclusion or goal, it searches for subgoals, which are conclusions that complete part of the current goal. The system continues this process until either the initial conclusion is satisfied or all subgoals are satisfied. The decision engine in Red Hat Decision Manager uses both forward and backward chaining to evaluate rules. The following diagram illustrates how the decision engine evaluates rules using forward chaining overall with a backward-chaining segment in the logic flow: Figure 21.4. Rule evaluation logic using forward and backward chaining In the State example, each State class has fields for its name and its current state (see the class org.drools.examples.state.State ). The following states are the two possible states for each object: NOTRUN FINISHED State class public class State { public static final int NOTRUN = 0; public static final int FINISHED = 1; private final PropertyChangeSupport changes = new PropertyChangeSupport( this ); private String name; private int state; ... setters and getters go here... } The State example contains two versions of the same example to resolve rule execution conflicts: A StateExampleUsingSalience version that resolves conflicts by using rule salience A StateExampleUsingAgendaGroups version that resolves conflicts by using rule agenda groups Both versions of the state example involve four State objects: A , B , C , and D . Initially, their states are set to NOTRUN , which is the default value for the constructor that the example uses. State example using salience The StateExampleUsingSalience version of the State example uses salience values in rules to resolve rule execution conflicts. Rules with a higher salience value are given higher priority when ordered in the activation queue. The example inserts each State instance into the KIE session and then calls fireAllRules() . Salience State example execution final State a = new State( "A" ); final State b = new State( "B" ); final State c = new State( "C" ); final State d = new State( "D" ); ksession.insert( a ); ksession.insert( b ); ksession.insert( c ); ksession.insert( d ); ksession.fireAllRules(); // Dispose KIE session if stateful (not required if stateless). ksession.dispose(); To execute the example, run the org.drools.examples.state.StateExampleUsingSalience class as a Java application in your IDE. After the execution, the following output appears in the IDE console window: Salience State example output in the IDE console Four rules are present. First, the "Bootstrap" rule fires, setting A to state FINISHED , which then causes B to change its state to FINISHED . Objects C and D are both dependent on B , causing a conflict that is resolved by the salience values. To better understand the execution flow of this example, you can load the audit log file from target/state.log into your IDE debug view or Audit View , if available (for example, in Window Show View in some IDEs). In this example, the Audit View shows that the assertion of the object A in the state NOTRUN activates the "Bootstrap" rule, while the assertions of the other objects have no immediate effect. Figure 21.5. Salience State example Audit View Rule "Bootstrap" in salience State example The execution of the "Bootstrap" rule changes the state of A to FINISHED , which activates rule "A to B" . Rule "A to B" in salience State example The execution of rule "A to B" changes the state of B to FINISHED , which activates both rules "B to C" and "B to D" , placing their activations onto the decision engine agenda. Rules "B to C" and "B to D" in salience State example From this point on, both rules may fire and, therefore, the rules are in conflict. The conflict resolution strategy enables the decision engine agenda to decide which rule to fire. Rule "B to C" has the higher salience value ( 10 versus the default salience value of 0 ), so it fires first, modifying object C to state FINISHED . The Audit View in your IDE shows the modification of the State object in the rule "A to B" , which results in two activations being in conflict. You can also use the Agenda View in your IDE to investigate the state of the decision engine agenda. In this example, the Agenda View shows the breakpoint in the rule "A to B" and the state of the agenda with the two conflicting rules. Rule "B to D" fires last, modifying object D to state FINISHED . Figure 21.6. Salience State example Agenda View State example using agenda groups The StateExampleUsingAgendaGroups version of the State example uses agenda groups in rules to resolve rule execution conflicts. Agenda groups enable you to partition the decision engine agenda to provide more execution control over groups of rules. By default, all rules are in the agenda group MAIN . You can use the agenda-group attribute to specify a different agenda group for the rule. Initially, a working memory has its focus on the agenda group MAIN . Rules in an agenda group only fire when the group receives the focus. You can set the focus either by using the method setFocus() or the rule attribute auto-focus . The auto-focus attribute enables the rule to be given a focus automatically for its agenda group when the rule is matched and activated. In this example, the auto-focus attribute enables rule "B to C" to fire before "B to D" . Rule "B to C" in agenda group State example The rule "B to C" calls setFocus() on the agenda group "B to D" , enabling its active rules to fire, which then enables the rule "B to D" to fire. Rule "B to D" in agenda group State example To execute the example, run the org.drools.examples.state.StateExampleUsingAgendaGroups class as a Java application in your IDE. After the execution, the following output appears in the IDE console window (same as the salience version of the State example): Agenda group State example output in the IDE console Dynamic facts in the State example Another notable concept in this State example is the use of dynamic facts , based on objects that implement a PropertyChangeListener object. In order for the decision engine to see and react to changes of fact properties, the application must notify the decision engine that changes occurred. You can configure this communication explicitly in the rules by using the modify statement, or implicitly by specifying that the facts implement the PropertyChangeSupport interface as defined by the JavaBeans specification. This example demonstrates how to use the PropertyChangeSupport interface to avoid the need for explicit modify statements in the rules. To make use of this interface, ensure that your facts implement PropertyChangeSupport in the same way that the class org.drools.example.State implements it, and then use the following code in the DRL rule file to configure the decision engine to listen for property changes on those facts: Declaring a dynamic fact When you use PropertyChangeListener objects, each setter must implement additional code for the notification. For example, the following setter for state is in the class org.drools.examples : Setter example with PropertyChangeSupport public void setState(final int newState) { int oldState = this.state; this.state = newState; this.changes.firePropertyChange( "state", oldState, newState ); } 21.4. Fibonacci example decisions (recursion and conflict resolution) The Fibonacci example decision set demonstrates how the decision engine uses recursion to resolve execution conflicts for rules in a sequence. The example focuses on resolving conflicts through salience values that you can define in rules. The following is an overview of the Fibonacci example: Name : fibonacci Main class : org.drools.examples.fibonacci.FibonacciExample (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.fibonacci.Fibonacci.drl (in src/main/resources ) Objective : Demonstrates recursion and conflict resolution through rule salience The Fibonacci Numbers form a sequence starting with 0 and 1. The Fibonacci number is obtained by adding the two preceding Fibonacci numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, and so on. The Fibonacci example uses the single fact class Fibonacci with the following two fields: sequence value The sequence field indicates the position of the object in the Fibonacci number sequence. The value field shows the value of that Fibonacci object for that sequence position, where -1 indicates a value that still needs to be computed. Fibonacci class public static class Fibonacci { private int sequence; private long value; public Fibonacci( final int sequence ) { this.sequence = sequence; this.value = -1; } ... setters and getters go here... } To execute the example, run the org.drools.examples.fibonacci.FibonacciExample class as a Java application in your IDE. After the execution, the following output appears in the IDE console window: Fibonacci example output in the IDE console To achieve this behavior in Java, the example inserts a single Fibonacci object with a sequence field of 50 . The example then uses a recursive rule to insert the other 49 Fibonacci objects. Instead of implementing the PropertyChangeSupport interface to use dynamic facts, this example uses the MVEL dialect modify keyword to enable a block setter action and notify the decision engine of changes. Fibonacci example execution ksession.insert( new Fibonacci( 50 ) ); ksession.fireAllRules(); This example uses the following three rules: "Recurse" "Bootstrap" "Calculate" The rule "Recurse" matches each asserted Fibonacci object with a value of -1 , creating and asserting a new Fibonacci object with a sequence of one less than the currently matched object. Each time a Fibonacci object is added while the one with a sequence field equal to 1 does not exist, the rule re-matches and fires again. The not conditional element is used to stop the rule matching once you have all 50 Fibonacci objects in memory. The rule also has a salience value because you need to have all 50 Fibonacci objects asserted before you execute the "Bootstrap" rule. Rule "Recurse" To better understand the execution flow of this example, you can load the audit log file from target/fibonacci.log into your IDE debug view or Audit View , if available (for example, in Window Show View in some IDEs). In this example, the Audit View shows the original assertion of the Fibonacci object with a sequence field of 50 , done from Java code. From there on, the Audit View shows the continual recursion of the rule, where each asserted Fibonacci object causes the "Recurse" rule to become activated and to fire again. Figure 21.7. Rule "Recurse" in Audit View When a Fibonacci object with a sequence field of 2 is asserted, the "Bootstrap" rule is matched and activated along with the "Recurse" rule. Notice the multiple restrictions on field sequence that test for equality with 1 or 2 : Rule "Bootstrap" You can also use the Agenda View in your IDE to investigate the state of the decision engine agenda. The "Bootstrap" rule does not fire yet because the "Recurse" rule has a higher salience value. Figure 21.8. Rules "Recurse" and "Bootstrap" in Agenda View 1 When a Fibonacci object with a sequence of 1 is asserted, the "Bootstrap" rule is matched again, causing two activations for this rule. The "Recurse" rule does not match and activate because the not conditional element stops the rule matching as soon as a Fibonacci object with a sequence of 1 exists. Figure 21.9. Rules "Recurse" and "Bootstrap" in Agenda View 2 The "Bootstrap" rule sets the objects with a sequence of 1 and 2 to a value of 1 . Now that you have two Fibonacci objects with values not equal to -1 , the "Calculate" rule is able to match. At this point in the example, nearly 50 Fibonacci objects exist in the working memory. You need to select a suitable triple to calculate each of their values in turn. If you use three Fibonacci patterns in a rule without field constraints to confine the possible cross products, the result would be 50x49x48 possible combinations, leading to about 125,000 possible rule firings, most of them incorrect. The "Calculate" rule uses field constraints to evaluate the three Fibonacci patterns in the correct order. This technique is called cross-product matching . The first pattern finds any Fibonacci object with a value != -1 and binds both the pattern and the field. The second Fibonacci object does the same thing, but adds an additional field constraint to ensure that its sequence is greater by one than the Fibonacci object bound to f1 . When this rule fires for the first time, you know that only sequences 1 and 2 have values of 1 , and the two constraints ensure that f1 references sequence 1 and that f2 references sequence 2 . The final pattern finds the Fibonacci object with a value equal to -1 and with a sequence one greater than f2 . At this point in the example, three Fibonacci objects are correctly selected from the available cross products, and you can calculate the value for the third Fibonacci object that is bound to f3 . Rule "Calculate" The modify statement updates the value of the Fibonacci object bound to f3 . This means that you now have another new Fibonacci object with a value not equal to -1 , which allows the "Calculate" rule to re-match and calculate the Fibonacci number. The debug view or Audit View of your IDE shows how the firing of the last "Bootstrap" rule modifies the Fibonacci object, enabling the "Calculate" rule to match, which then modifies another Fibonacci object that enables the "Calculate" rule to match again. This process continues until the value is set for all Fibonacci objects. Figure 21.10. Rules in Audit View 21.5. Pricing example decisions (decision tables) The Pricing example decision set demonstrates how to use a spreadsheet decision table for calculating the retail cost of an insurance policy in tabular format instead of directly in a DRL file. The following is an overview of the Pricing example: Name : decisiontable Main class : org.drools.examples.decisiontable.PricingRuleDTExample (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.decisiontable.ExamplePolicyPricing.xls (in src/main/resources ) Objective : Demonstrates use of spreadsheet decision tables to define rules Spreadsheet decision tables are XLS or XLSX spreadsheets that contain business rules defined in a tabular format. You can include spreadsheet decision tables with standalone Red Hat Decision Manager projects or upload them to projects in Business Central. Each row in a decision table is a rule, and each column is a condition, an action, or another rule attribute. After you create and upload your decision tables into your Red Hat Decision Manager project, the rules you defined are compiled into Drools Rule Language (DRL) rules as with all other rule assets. The purpose of the Pricing example is to provide a set of business rules to calculate the base price and a discount for a car driver applying for a specific type of insurance policy. The driver's age and history and the policy type all contribute to calculate the basic premium, and additional rules calculate potential discounts for which the driver might be eligible. To execute the example, run the org.drools.examples.decisiontable.PricingRuleDTExample class as a Java application in your IDE. After the execution, the following output appears in the IDE console window: The code to execute the example follows the typical execution pattern: the rules are loaded, the facts are inserted, and a stateless KIE session is created. The difference in this example is that the rules are defined in an ExamplePolicyPricing.xls file instead of a DRL file or other source. The spreadsheet file is loaded into the decision engine using templates and DRL rules. Spreadsheet decision table setup The ExamplePolicyPricing.xls spreadsheet contains two decision tables in the first tab: Base pricing rules Promotional discount rules As the example spreadsheet demonstrates, you can use only the first tab of a spreadsheet to create decision tables, but multiple tables can be within a single tab. Decision tables do not necessarily follow top-down logic, but are more of a means to capture data resulting in rules. The evaluation of the rules is not necessarily in the given order, because all of the normal mechanics of the decision engine still apply. This is why you can have multiple decision tables in the same tab of a spreadsheet. The decision tables are executed through the corresponding rule template files BasePricing.drt and PromotionalPricing.drt . These template files reference the decision tables through their template parameter and directly reference the various headers for the conditions and actions in the decision tables. BasePricing.drt rule template file PromotionalPricing.drt rule template file The rules are executed through the kmodule.xml reference of the KIE Session DTableWithTemplateKB , which specifically mentions the ExamplePolicyPricing.xls spreadsheet and is required for successful execution of the rules. This execution method enables you to execute the rules as a standalone unit (as in this example) or to include the rules in a packaged knowledge JAR (KJAR) file, so that the spreadsheet is packaged along with the rules for execution. The following section of the kmodule.xml file is required for the execution of the rules and spreadsheet to work successfully: <kbase name="DecisionTableKB" packages="org.drools.examples.decisiontable"> <ksession name="DecisionTableKS" type="stateless"/> </kbase> <kbase name="DTableWithTemplateKB" packages="org.drools.examples.decisiontable-template"> <ruleTemplate dtable="org/drools/examples/decisiontable-template/ExamplePolicyPricingTemplateData.xls" template="org/drools/examples/decisiontable-template/BasePricing.drt" row="3" col="3"/> <ruleTemplate dtable="org/drools/examples/decisiontable-template/ExamplePolicyPricingTemplateData.xls" template="org/drools/examples/decisiontable-template/PromotionalPricing.drt" row="18" col="3"/> <ksession name="DTableWithTemplateKS"/> </kbase> As an alternative to executing the decision tables using rule template files, you can use the DecisionTableConfiguration object and specify an input spreadsheet as the input type, such as DecisionTableInputType.xls : DecisionTableConfiguration dtableconfiguration = KnowledgeBuilderFactory.newDecisionTableConfiguration(); dtableconfiguration.setInputType( DecisionTableInputType.XLS ); KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); Resource xlsRes = ResourceFactory.newClassPathResource( "ExamplePolicyPricing.xls", getClass() ); kbuilder.add( xlsRes, ResourceType.DTABLE, dtableconfiguration ); The Pricing example uses two fact types: Driver Policy . The example sets the default values for both facts in their respective Java classes Driver.java and Policy.java . The Driver is 30 years old, has had no prior claims, and currently has a risk profile of LOW . The Policy that the driver is applying for is COMPREHENSIVE . In any decision table, each row is considered a different rule and each column is a condition or an action. Each row is evaluated in a decision table unless the agenda is cleared upon execution. Decision table spreadsheets (XLS or XLSX) require two key areas that define rule data: A RuleSet area A RuleTable area The RuleSet area of the spreadsheet defines elements that you want to apply globally to all rules in the same package (not only the spreadsheet), such as a rule set name or universal rule attributes. The RuleTable area defines the actual rules (rows) and the conditions, actions, and other rule attributes (columns) that constitute that rule table within the specified rule set. A decision table spreadsheet can contain multiple RuleTable areas, but only one RuleSet area. Figure 21.11. Decision table configuration The RuleTable area also defines the objects to which the rule attributes apply, in this case Driver and Policy , followed by constraints on the objects. For example, the Driver object constraint that defines the Age Bracket column is age >= USD1, age <= USD2 , where the comma-separated range is defined in the table column values, such as 18,24 . Base pricing rules The Base pricing rules decision table in the Pricing example evaluates the age, risk profile, number of claims, and policy type of the driver and produces the base price of the policy based on these conditions. Figure 21.12. Base price calculation The Driver attributes are defined in the following table columns: Age Bracket : The age bracket has a definition for the condition age >=USD1, age <=USD2 , which defines the condition boundaries for the driver's age. This condition column highlights the use of USD1 and USD2 , which is comma delimited in the spreadsheet. You can write these values as 18,24 or 18, 24 and both formats work in the execution of the business rules. Location risk profile : The risk profile is a string that the example program passes always as LOW but can be changed to reflect MED or HIGH . Number of prior claims : The number of claims is defined as an integer that the condition column must exactly equal to trigger the action. The value is not a range, only exact matches. The Policy of the decision table is used in both the conditions and the actions of the rule and has attributes defined in the following table columns: Policy type applying for : The policy type is a condition that is passed as a string that defines the type of coverage: COMPREHENSIVE , FIRE_THEFT , or THIRD_PARTY . Base USD AUD : The basePrice is defined as an ACTION that sets the price through the constraint policy.setBasePrice(USDparam); based on the spreadsheet cells corresponding to this value. When you execute the corresponding DRL rule for this decision table, the then portion of the rule executes this action statement on the true conditions matching the facts and sets the base price to the corresponding value. Record Reason : When the rule successfully executes, this action generates an output message to the System.out console reflecting which rule fired. This is later captured in the application and printed. The example also uses the first column on the left to categorize rules. This column is for annotation only and has no affect on rule execution. Promotional discount rules The Promotional discount rules decision table in the Pricing example evaluates the age, number of prior claims, and policy type of the driver to generate a potential discount on the price of the insurance policy. Figure 21.13. Discount calculation This decision table contains the conditions for the discount for which the driver might be eligible. Similar to the base price calculation, this table evaluates the Age , Number of prior claims of the driver, and the Policy type applying for to determine a Discount % rate to be applied. For example, if the driver is 30 years old, has no prior claims, and is applying for a COMPREHENSIVE policy, the driver is given a discount of 20 percent. 21.6. Pet Store example decisions (agenda groups, global variables, callbacks, and GUI integration) The Pet Store example decision set demonstrates how to use agenda groups and global variables in rules and how to integrate Red Hat Decision Manager rules with a graphical user interface (GUI), in this case a Swing-based desktop application. The example also demonstrates how to use callbacks to interact with a running decision engine to update the GUI based on changes in the working memory at run time. The following is an overview of the Pet Store example: Name : petstore Main class : org.drools.examples.petstore.PetStoreExample (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.petstore.PetStore.drl (in src/main/resources ) Objective : Demonstrates rule agenda groups, global variables, callbacks, and GUI integration In the Pet Store example, the sample PetStoreExample.java class defines the following principal classes (in addition to several classes to handle Swing events): Petstore contains the main() method. PetStoreUI is responsible for creating and displaying the Swing-based GUI. This class contains several smaller classes, mainly for responding to various GUI events, such as user mouse clicks. TableModel holds the table data. This class is essentially a JavaBean that extends the Swing class AbstractTableModel . CheckoutCallback enables the GUI to interact with the rules. Ordershow keeps the items that you want to buy. Purchase stores details of the order and the products that you are buying. Product is a JavaBean containing details of the product available for purchase and its price. Much of the Java code in this example is either plain JavaBean or Swing based. For more information about Swing components, see the Java tutorial on Creating a GUI with JFC/Swing . Rule execution behavior in the Pet Store example Unlike other example decision sets where the facts are asserted and fired immediately, the Pet Store example does not execute the rules until more facts are gathered based on user interaction. The example executes rules through a PetStoreUI object, created by a constructor, that accepts the Vector object stock for collecting the products. The example then uses an instance of the CheckoutCallback class containing the rule base that was previously loaded. Pet Store KIE container and fact execution setup // KieServices is the factory for all KIE services. KieServices ks = KieServices.Factory.get(); // Create a KIE container on the class path. KieContainer kc = ks.getKieClasspathContainer(); // Create the stock. Vector<Product> stock = new Vector<Product>(); stock.add( new Product( "Gold Fish", 5 ) ); stock.add( new Product( "Fish Tank", 25 ) ); stock.add( new Product( "Fish Food", 2 ) ); // A callback is responsible for populating the working memory and for firing all rules. PetStoreUI ui = new PetStoreUI( stock, new CheckoutCallback( kc ) ); ui.createAndShowGUI(); The Java code that fires the rules is in the CheckoutCallBack.checkout() method. This method is triggered when the user clicks Checkout in the UI. Rule execution from CheckoutCallBack.checkout() public String checkout(JFrame frame, List<Product> items) { Order order = new Order(); // Iterate through list and add to cart. for ( Product p: items ) { order.addItem( new Purchase( order, p ) ); } // Add the JFrame to the ApplicationData to allow for user interaction. // From the KIE container, a KIE session is created based on // its definition and configuration in the META-INF/kmodule.xml file. KieSession ksession = kcontainer.newKieSession("PetStoreKS"); ksession.setGlobal( "frame", frame ); ksession.setGlobal( "textArea", this.output ); ksession.insert( new Product( "Gold Fish", 5 ) ); ksession.insert( new Product( "Fish Tank", 25 ) ); ksession.insert( new Product( "Fish Food", 2 ) ); ksession.insert( new Product( "Fish Food Sample", 0 ) ); ksession.insert( order ); // Execute rules. ksession.fireAllRules(); // Return the state of the cart return order.toString(); } The example code passes two elements into the CheckoutCallBack.checkout() method. One element is the handle for the JFrame Swing component surrounding the output text frame, found at the bottom of the GUI. The second element is a list of order items, which comes from the TableModel that stores the information from the Table area at the upper-right section of the GUI. The for loop transforms the list of order items coming from the GUI into the Order JavaBean, also contained in the file PetStoreExample.java . In this case, the rule is firing in a stateless KIE session because all of the data is stored in Swing components and is not executed until the user clicks Checkout in the UI. Each time the user clicks Checkout , the content of the list is moved from the Swing TableModel into the KIE session working memory and is then executed with the ksession.fireAllRules() method. Within this code, there are nine calls to KieSession . The first of these creates a new KieSession from the KieContainer (the example passed in this KieContainer from the CheckoutCallBack class in the main() method). The two calls pass in the two objects that hold the global variables in the rules: the Swing text area and the Swing frame used for writing messages. More inserts put information on products into the KieSession , as well as the order list. The final call is the standard fireAllRules() . Pet Store rule file imports, global variables, and Java functions The PetStore.drl file contains the standard package and import statements to make various Java classes available to the rules. The rule file also includes global variables to be used within the rules, defined as frame and textArea . The global variables hold references to the Swing components JFrame and JTextArea components that were previously passed on by the Java code that called the setGlobal() method. Unlike standard variables in rules, which expire as soon as the rule has fired, global variables retain their value for the lifetime of the KIE session. This means the contents of these global variables are available for evaluation on all subsequent rules. PetStore.drl package, imports, and global variables package org.drools.examples; import org.kie.api.runtime.KieRuntime; import org.drools.examples.petstore.PetStoreExample.Order; import org.drools.examples.petstore.PetStoreExample.Purchase; import org.drools.examples.petstore.PetStoreExample.Product; import java.util.ArrayList; import javax.swing.JOptionPane; import javax.swing.JFrame; global JFrame frame global javax.swing.JTextArea textArea The PetStore.drl file also contains two functions that the rules in the file use: PetStore.drl Java functions function void doCheckout(JFrame frame, KieRuntime krt) { Object[] options = {"Yes", "No"}; int n = JOptionPane.showOptionDialog(frame, "Would you like to checkout?", "", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]); if (n == 0) { krt.getAgenda().getAgendaGroup( "checkout" ).setFocus(); } } function boolean requireTank(JFrame frame, KieRuntime krt, Order order, Product fishTank, int total) { Object[] options = {"Yes", "No"}; int n = JOptionPane.showOptionDialog(frame, "Would you like to buy a tank for your " + total + " fish?", "Purchase Suggestion", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]); System.out.print( "SUGGESTION: Would you like to buy a tank for your " + total + " fish? - " ); if (n == 0) { Purchase purchase = new Purchase( order, fishTank ); krt.insert( purchase ); order.addItem( purchase ); System.out.println( "Yes" ); } else { System.out.println( "No" ); } return true; } The two functions perform the following actions: doCheckout() displays a dialog that asks the user if she or he wants to check out. If the user does, the focus is set to the checkout agenda group, enabling rules in that group to (potentially) fire. requireTank() displays a dialog that asks the user if she or he wants to buy a fish tank. If the user does, a new fish tank Product is added to the order list in the working memory. Note For this example, all rules and functions are within the same rule file for efficiency. In a production environment, you typically separate the rules and functions in different files or build a static Java method and import the files using the import function, such as import function my.package.name.hello . Pet Store rules with agenda groups Most of the rules in the Pet Store example use agenda groups to control rule execution. Agenda groups allow you to partition the decision engine agenda to provide more execution control over groups of rules. By default, all rules are in the agenda group MAIN . You can use the agenda-group attribute to specify a different agenda group for the rule. Initially, a working memory has its focus on the agenda group MAIN . Rules in an agenda group only fire when the group receives the focus. You can set the focus either by using the method setFocus() or the rule attribute auto-focus . The auto-focus attribute enables the rule to be given a focus automatically for its agenda group when the rule is matched and activated. The Pet Store example uses the following agenda groups for rules: "init" "evaluate" "show items" "checkout" For example, the sample rule "Explode Cart" uses the "init" agenda group to ensure that it has the option to fire and insert shopping cart items into the KIE session working memory: Rule "Explode Cart" This rule matches against all orders that do not yet have their grossTotal calculated. The execution loops for each purchase item in that order. The rule uses the following features related to its agenda group: agenda-group "init" defines the name of the agenda group. In this case, only one rule is in the group. However, neither the Java code nor a rule consequence sets the focus to this group, and therefore it relies on the auto-focus attribute for its chance to fire. auto-focus true ensures that this rule, while being the only rule in the agenda group, gets a chance to fire when fireAllRules() is called from the Java code. kcontext... .setFocus() sets the focus to the "show items" and "evaluate" agenda groups, enabling their rules to fire. In practice, you loop through all items in the order, insert them into memory, and then fire the other rules after each insertion. The "show items" agenda group contains only one rule, "Show Items" . For each purchase in the order currently in the KIE session working memory, the rule logs details to the text area at the bottom of the GUI, based on the textArea variable defined in the rule file. Rule "Show Items" The "evaluate" agenda group also gains focus from the "Explode Cart" rule. This agenda group contains two rules, "Free Fish Food Sample" and "Suggest Tank" , which are executed in that order. Rule "Free Fish Food Sample" The rule "Free Fish Food Sample" fires only if all of the following conditions are true: 1 The agenda group "evaluate" is being evaluated in the rules execution. 2 User does not already have fish food. 3 User does not already have a free fish food sample. 4 User has a goldfish in the order. If the order facts meet all of these requirements, then a new product is created (Fish Food Sample) and is added to the order in working memory. Rule "Suggest Tank" The rule "Suggest Tank" fires only if the following conditions are true: 1 User does not have a fish tank in the order. 2 User has more than five fish in the order. When the rule fires, it calls the requireTank() function defined in the rule file. This function displays a dialog that asks the user if she or he wants to buy a fish tank. If the user does, a new fish tank Product is added to the order list in the working memory. When the rule calls the requireTank() function, the rule passes the frame global variable so that the function has a handle for the Swing GUI. The "do checkout" rule in the Pet Store example has no agenda group and no when conditions, so the rule is always executed and considered part of the default MAIN agenda group. Rule "do checkout" When the rule fires, it calls the doCheckout() function defined in the rule file. This function displays a dialog that asks the user if she or he wants to check out. If the user does, the focus is set to the checkout agenda group, enabling rules in that group to (potentially) fire. When the rule calls the doCheckout() function, the rule passes the frame global variable so that the function has a handle for the Swing GUI. Note This example also demonstrates a troubleshooting technique if results are not executing as you expect: You can remove the conditions from the when statement of a rule and test the action in the then statement to verify that the action is performed correctly. The "checkout" agenda group contains three rules for processing the order checkout and applying any discounts: "Gross Total" , "Apply 5% Discount" , and "Apply 10% Discount" . Rules "Gross Total", "Apply 5% Discount", and "Apply 10% Discount" If the user has not already calculated the gross total, the Gross Total accumulates the product prices into a total, puts this total into the KIE session, and displays it through the Swing JTextArea using the textArea global variable. If the gross total is between 10 and 20 (currency units), the "Apply 5% Discount" rule calculates the discounted total, adds it to the KIE session, and displays it in the text area. If the gross total is not less than 20 , the "Apply 10% Discount" rule calculates the discounted total, adds it to the KIE session, and displays it in the text area. Pet Store example execution Similar to other Red Hat Decision Manager decision examples, you execute the Pet Store example by running the org.drools.examples.petstore.PetStoreExample class as a Java application in your IDE. When you execute the Pet Store example, the Pet Store Demo GUI window appears. This window displays a list of available products (upper left), an empty list of selected products (upper right), Checkout and Reset buttons (middle), and an empty system messages area (bottom). Figure 21.14. Pet Store example GUI after launch The following events occurred in this example to establish this execution behavior: The main() method has run and loaded the rule base but has not yet fired the rules. So far, this is the only code in connection with rules that has been run. A new PetStoreUI object has been created and given a handle for the rule base, for later use. Various Swing components have performed their functions, and the initial UI screen is displayed and waits for user input. You can click various products from the list to explore the UI setup: Figure 21.15. Explore the Pet Store example GUI No rules code has been fired yet. The UI uses Swing code to detect user mouse clicks and add selected products to the TableModel object for display in the upper-right corner of the UI. This example illustrates the Model-View-Controller design pattern. When you click Checkout , the rules are then fired in the following way: Method CheckOutCallBack.checkout() is called (eventually) by the Swing class waiting for a user to click Checkout . This inserts the data from the TableModel object (upper-right corner of the UI) into the KIE session working memory. The method then fires the rules. The "Explode Cart" rule is the first to fire, with the auto-focus attribute set to true . The rule loops through all of the products in the cart, ensures that the products are in the working memory, and then gives the "show Items" and "evaluate" agenda groups the option to fire. The rules in these groups add the contents of the cart to the text area (bottom of the UI), evaluate if you are eligible for free fish food, and determine whether to ask if you want to buy a fish tank. Figure 21.16. Fish tank qualification The "do checkout" rule is the to fire because no other agenda group currently has focus and because it is part of the default MAIN agenda group. This rule always calls the doCheckout() function, which asks you if you want to check out. The doCheckout() function sets the focus to the "checkout" agenda group, giving the rules in that group the option to fire. The rules in the "checkout" agenda group display the contents of the cart and apply the appropriate discount. Swing then waits for user input to either select more products (and cause the rules to fire again) or to close the UI. Figure 21.17. Pet Store example GUI after all rules have fired You can add more System.out calls to demonstrate this flow of events in your IDE console: System.out output in the IDE console 21.7. Honest Politician example decisions (truth maintenance and salience) The Honest Politician example decision set demonstrates the concept of truth maintenance with logical insertions and the use of salience in rules. The following is an overview of the Honest Politician example: Name : honestpolitician Main class : org.drools.examples.honestpolitician.HonestPoliticianExample (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.honestpolitician.HonestPolitician.drl (in src/main/resources ) Objective : Demonstrates the concept of truth maintenance based on the logical insertion of facts and the use of salience in rules The basic premise of the Honest Politician example is that an object can only exist while a statement is true. A rule consequence can logically insert an object with the insertLogical() method. This means the object remains in the KIE session working memory as long as the rule that logically inserted it remains true. When the rule is no longer true, the object is automatically retracted. In this example, rule execution causes a group of politicians to change from being honest to being dishonest as a result of a corrupt corporation. As each politician is evaluated, they start out with their honesty attribute being set to true , but a rule fires that makes the politicians no longer honest. As they switch their state from being honest to dishonest, they are then removed from the working memory. The rule salience notifies the decision engine how to prioritize any rules that have a salience defined for them, otherwise utilizing the default salience value of 0 . Rules with a higher salience value are given higher priority when ordered in the activation queue. Politician and Hope classes The sample class Politician in the example is configured for an honest politician. The Politician class is made up of a String item name and a Boolean item honest : Politician class public class Politician { private String name; private boolean honest; ... } The Hope class determines if a Hope object exists. This class has no meaningful members, but is present in the working memory as long as society has hope. Hope class public class Hope { public Hope() { } } Rule definitions for politician honesty In the Honest Politician example, when at least one honest politician exists in the working memory, the "We have an honest Politician" rule logically inserts a new Hope object. As soon as all politicians become dishonest, the Hope object is automatically retracted. This rule has a salience attribute with a value of 10 to ensure that it fires before any other rule, because at that stage the "Hope is Dead" rule is true. Rule "We have an honest politician" As soon as a Hope object exists, the "Hope Lives" rule matches and fires. This rule also has a salience value of 10 so that it takes priority over the "Corrupt the Honest" rule. Rule "Hope Lives" Initially, four honest politicians exist so this rule has four activations, all in conflict. Each rule fires in turn, corrupting each politician so that they are no longer honest. When all four politicians have been corrupted, no politicians have the property honest == true . The rule "We have an honest Politician" is no longer true and the object it logically inserted (due to the last execution of new Hope() ) is automatically retracted. Rule "Corrupt the Honest" With the Hope object automatically retracted through the truth maintenance system, the conditional element not applied to Hope is no longer true so that the "Hope is Dead" rule matches and fires. Rule "Hope is Dead" Example execution and audit trail In the HonestPoliticianExample.java class, the four politicians with the honest state set to true are inserted for evaluation against the defined business rules: HonestPoliticianExample.java class execution public static void execute( KieContainer kc ) { KieSession ksession = kc.newKieSession("HonestPoliticianKS"); final Politician p1 = new Politician( "President of Umpa Lumpa", true ); final Politician p2 = new Politician( "Prime Minster of Cheeseland", true ); final Politician p3 = new Politician( "Tsar of Pringapopaloo", true ); final Politician p4 = new Politician( "Omnipotence Om", true ); ksession.insert( p1 ); ksession.insert( p2 ); ksession.insert( p3 ); ksession.insert( p4 ); ksession.fireAllRules(); ksession.dispose(); } To execute the example, run the org.drools.examples.honestpolitician.HonestPoliticianExample class as a Java application in your IDE. After the execution, the following output appears in the IDE console window: Execution output in the IDE console The output shows that, while there is at least one honest politician, democracy lives. However, as each politician is corrupted by some corporation, all politicians become dishonest, and democracy is dead. To better understand the execution flow of this example, you can modify the HonestPoliticianExample.java class to include a DebugRuleRuntimeEventListener listener and an audit logger to view execution details: HonestPoliticianExample.java class with an audit logger package org.drools.examples.honestpolitician; import org.kie.api.KieServices; import org.kie.api.event.rule.DebugAgendaEventListener; 1 import org.kie.api.event.rule.DebugRuleRuntimeEventListener; import org.kie.api.runtime.KieContainer; import org.kie.api.runtime.KieSession; public class HonestPoliticianExample { /** * @param args */ public static void main(final String[] args) { KieServices ks = KieServices.Factory.get(); 2 //ks = KieServices.Factory.get(); KieContainer kc = KieServices.Factory.get().getKieClasspathContainer(); System.out.println(kc.verify().getMessages().toString()); //execute( kc ); execute( ks, kc); 3 } public static void execute( KieServices ks, KieContainer kc ) { 4 KieSession ksession = kc.newKieSession("HonestPoliticianKS"); final Politician p1 = new Politician( "President of Umpa Lumpa", true ); final Politician p2 = new Politician( "Prime Minster of Cheeseland", true ); final Politician p3 = new Politician( "Tsar of Pringapopaloo", true ); final Politician p4 = new Politician( "Omnipotence Om", true ); ksession.insert( p1 ); ksession.insert( p2 ); ksession.insert( p3 ); ksession.insert( p4 ); // The application can also setup listeners 5 ksession.addEventListener( new DebugAgendaEventListener() ); ksession.addEventListener( new DebugRuleRuntimeEventListener() ); // Set up a file-based audit logger. ks.getLoggers().newFileLogger( ksession, "./target/honestpolitician" ); 6 ksession.fireAllRules(); ksession.dispose(); } } 1 Adds to your imports the packages that handle the DebugAgendaEventListener and DebugRuleRuntimeEventListener 2 Creates a KieServices Factory and a ks element to produce the logs because this audit log is not available at the KieContainer level 3 Modifies the execute method to use both KieServices and KieContainer 4 Modifies the execute method to pass in KieServices in addition to the KieContainer 5 Creates the listeners 6 Builds the log that can be passed into the debug view or Audit View or your IDE after executing of the rules When you run the Honest Politician with this modified logging capability, you can load the audit log file from target/honestpolitician.log into your IDE debug view or Audit View , if available (for example, in Window Show View in some IDEs). In this example, the Audit View shows the flow of executions, insertions, and retractions as defined in the example classes and rules: Figure 21.18. Honest Politician example Audit View When the first politician is inserted, two activations occur. The rule "We have an honest Politician" is activated only one time for the first inserted politician because it uses an exists conditional element, which matches when at least one politician is inserted. The rule "Hope is Dead" is also activated at this stage because the Hope object is not yet inserted. The rule "We have an honest Politician" fires first because it has a higher salience value than the rule "Hope is Dead" , and inserts the Hope object (highlighted in green). The insertion of the Hope object activates the rule "Hope Lives" and deactivates the rule "Hope is Dead" . The insertion also activates the rule "Corrupt the Honest" for each inserted honest politician. The rule "Hope Lives" is executed and prints "Hurrah!!! Democracy Lives" . , for each politician, the rule "Corrupt the Honest" fires, printing "I'm an evil corporation and I have corrupted X" , where X is the name of the politician, and modifies the politician honesty value to false . When the last honest politician is corrupted, Hope is automatically retracted by the truth maintenance system (highlighted in blue). The green highlighted area shows the origin of the currently selected blue highlighted area. After the Hope fact is retracted, the rule "Hope is dead" fires, printing "We are all Doomed!!! Democracy is Dead" . 21.8. Sudoku example decisions (complex pattern matching, callbacks, and GUI integration) The Sudoku example decision set, based on the popular number puzzle Sudoku, demonstrates how to use rules in Red Hat Decision Manager to find a solution in a large potential solution space based on various constraints. This example also shows how to integrate Red Hat Decision Manager rules into a graphical user interface (GUI), in this case a Swing-based desktop application, and how to use callbacks to interact with a running decision engine to update the GUI based on changes in the working memory at run time. The following is an overview of the Sudoku example: Name : sudoku Main class : org.drools.examples.sudoku.SudokuExample (in src/main/java ) Module : drools-examples Type : Java application Rule files : org.drools.examples.sudoku.*.drl (in src/main/resources ) Objective : Demonstrates complex pattern matching, problem solving, callbacks, and GUI integration Sudoku is a logic-based number placement puzzle. The objective is to fill a 9x9 grid so that each column, each row, and each of the nine 3x3 zones contains the digits from 1 to 9 only one time. The puzzle setter provides a partially completed grid and the puzzle solver's task is to complete the grid with these constraints. The general strategy to solve the problem is to ensure that when you insert a new number, it must be unique in its particular 3x3 zone, row, and column. This Sudoku example decision set uses Red Hat Decision Manager rules to solve Sudoku puzzles from a range of difficulty levels, and to attempt to resolve flawed puzzles that contain invalid entries. Sudoku example execution and interaction Similar to other Red Hat Decision Manager decision examples, you execute the Sudoku example by running the org.drools.examples.sudoku.SudokuExample class as a Java application in your IDE. When you execute the Sudoku example, the Drools Sudoku Example GUI window appears. This window contains an empty grid, but the program comes with various grids stored internally that you can load and solve. Click File Samples Simple to load one of the examples. Notice that all buttons are disabled until a grid is loaded. Figure 21.19. Sudoku example GUI after launch When you load the Simple example, the grid is filled according to the puzzle's initial state. Figure 21.20. Sudoku example GUI after loading Simple sample Choose from the following options: Click Solve to fire the rules defined in the Sudoku example that fill out the remaining values and that make the buttons inactive again. Figure 21.21. Simple sample solved Click Step to see the digit found by the rule set. The console window in your IDE displays detailed information about the rules that are executing to solve the step. Step execution output in the IDE console Click Dump to see the state of the grid, with cells showing either the established value or the remaining possibilities. Dump execution output in the IDE console The Sudoku example includes a deliberately broken sample file that the rules defined in the example can resolve. Click File Samples !DELIBERATELY BROKEN! to load the broken sample. The grid starts with some issues, for example, the value 5 appears two times in the first row, which is not allowed. Figure 21.22. Broken Sudoku example initial state Click Solve to apply the solving rules to this invalid grid. The associated solving rules in the Sudoku example detect the issues in the sample and attempts to solve the puzzle as far as possible. This process does not complete and leaves some cells empty. The solving rule activity is displayed in the IDE console window: Detected issues in the broken sample Figure 21.23. Broken sample solution attempt The sample Sudoku files labeled Hard are more complex and the solving rules might not be able to solve them. The unsuccessful solution attempt is displayed in the IDE console window: Hard sample unresolved The rules that work to solve the broken sample implement standard solving techniques based on the sets of values that are still candidates for a cell. For example, if a set contains a single value, then this is the value for the cell. For a single occurrence of a value in one of the groups of nine cells, the rules insert a fact of type Setting with the solution value for some specific cell. This fact causes the elimination of this value from all other cells in any of the groups the cell belongs to and the value is retracted. Other rules in the example reduce the permissible values for some cells. The rules "naked pair" , "hidden pair in row" , "hidden pair in column" , and "hidden pair in square" eliminate possibilities but do not establish solutions. The rules "X-wings in rows" , "`X-wings in columns"`, "intersection removal row" , and "intersection removal column" perform more sophisticated eliminations. Sudoku example classes The package org.drools.examples.sudoku.swing contains the following core set of classes that implement a framework for Sudoku puzzles: The SudokuGridModel class defines an interface that is implemented to store a Sudoku puzzle as a 9x9 grid of Cell objects. The SudokuGridView class is a Swing component that can visualize any implementation of the SudokuGridModel class. The SudokuGridEvent and SudokuGridListener classes communicate state changes between the model and the view. Events are fired when a cell value is resolved or changed. The SudokuGridSamples class provides partially filled Sudoku puzzles for demonstration purposes. Note This package does not have any dependencies on Red Hat Decision Manager libraries. The package org.drools.examples.sudoku contains the following core set of classes that implement the elementary Cell object and its various aggregations: The CellFile class, with subtypes CellRow , CellCol , and CellSqr , all of which are subtypes of the CellGroup class. The Cell and CellGroup subclasses of SetOfNine , which provides a property free with the type Set<Integer> . For a Cell class, the set represents the individual candidate set. For a CellGroup class, the set is the union of all candidate sets of its cells (the set of digits that still need to be allocated). In the Sudoku example are 81 Cell and 27 CellGroup objects and a linkage provided by the Cell properties cellRow , cellCol , and cellSqr , and by the CellGroup property cells (a list of Cell objects). With these components, you can write rules that detect the specific situations that permit the allocation of a value to a cell or the elimination of a value from some candidate set. The Setting class is used to trigger the operations that accompany the allocation of a value. The presence of a Setting fact is used in all rules that detect a new situation in order to avoid reactions to inconsistent intermediary states. The Stepping class is used in a low priority rule to execute an emergency halt when a "Step" does not terminate regularly. This behavior indicates that the program cannot solve the puzzle. The main class org.drools.examples.sudoku.SudokuExample implements a Java application combining all of these components. Sudoku validation rules (validate.drl) The validate.drl file in the Sudoku example contains validation rules that detect duplicate numbers in cell groups. They are combined in a "validate" agenda group that enables the rules to be explicitly activated after a user loads the puzzle. The when conditions of the three rules "duplicate in cell ... " all function in the following ways: The first condition in the rule locates a cell with an allocated value. The second condition in the rule pulls in any of the three cell groups to which the cell belongs. The final condition finds a cell (other than the first one) with the same value as the first cell and in the same row, column, or square, depending on the rule. Rules "duplicate in cell ... " The rule "terminate group" is the last to fire. This rule prints a message and stops the sequence. Rule "terminate group" Sudoku solving rules (sudoku.drl) The sudoku.drl file in the Sudoku example contains three types of rules: one group handles the allocation of a number to a cell, another group detects feasible allocations, and the third group eliminates values from candidate sets. The rules "set a value" , "eliminate a value from Cell" , and "retract setting" depend on the presence of a Setting object. The first rule handles the assignment to the cell and the operations for removing the value from the free sets of the three groups of the cell. This group also reduces a counter that, when zero, returns control to the Java application that has called fireUntilHalt() . The purpose of the rule "eliminate a value from Cell" is to reduce the candidate lists of all cells that are related to the newly assigned cell. Finally, when all eliminations have been made, the rule "retract setting" retracts the triggering Setting fact. Rules "set a value", "eliminate a value from a Cell", and "retract setting" Two solving rules detect a situation where an allocation of a number to a cell is possible. The rule "single" fires for a Cell with a candidate set containing a single number. The rule "hidden single" fires when no cell exists with a single candidate, but when a cell exists containing a candidate, this candidate is absent from all other cells in one of the three groups to which the cell belongs. Both rules create and insert a Setting fact. Rules "single" and "hidden single" Rules from the largest group, either individually or in groups of two or three, implement various solving techniques used for solving Sudoku puzzles manually. The rule "naked pair" detects identical candidate sets of size 2 in two cells of a group. These two values may be removed from all other candidate sets of that group. Rule "naked pair" The three rules "hidden pair in ... " functions similarly to the rule "naked pair" . These rules detect a subset of two numbers in exactly two cells of a group, with neither value occurring in any of the other cells of the group. This means that all other candidates can be eliminated from the two cells harboring the hidden pair. Rules "hidden pair in ... " Two rules deal with "X-wings" in rows and columns. When only two possible cells for a value exist in each of two different rows (or columns) and these candidates lie also in the same columns (or rows), then all other candidates for this value in the columns (or rows) can be eliminated. When you follow the pattern sequence in one of these rules, notice how the conditions that are conveniently expressed by words such as same or only result in patterns with suitable constraints or that are prefixed with not . Rules "X-wings in ... " The two rules "intersection removal ... " are based on the restricted occurrence of some number within one square, either in a single row or in a single column. This means that this number must be in one of those two or three cells of the row or column and can be removed from the candidate sets of all other cells of the group. The pattern establishes the restricted occurrence and then fires for each cell outside of the square and within the same cell file. Rules "intersection removal ... " These rules are sufficient for many but not all Sudoku puzzles. To solve very difficult grids, the rule set requires more complex rules. (Ultimately, some puzzles can be solved only by trial and error.) 21.9. Conway's Game of Life example decisions (ruleflow groups and GUI integration) The Conway's Game of Life example decision set, based on the famous cellular automaton by John Conway, demonstrates how to use ruleflow groups in rules to control rule execution. The example also demonstrates how to integrate Red Hat Decision Manager rules with a graphical user interface (GUI), in this case a Swing-based implementation of Conway's Game of Life. The following is an overview of the Conway's Game of Life (Conway) example: Name : conway Main classes : org.drools.examples.conway.ConwayRuleFlowGroupRun , org.drools.examples.conway.ConwayAgendaGroupRun (in src/main/java ) Module : droolsjbpm-integration-examples Type : Java application Rule files : org.drools.examples.conway.*.drl (in src/main/resources ) Objective : Demonstrates ruleflow groups and GUI integration Note The Conway's Game of Life example is separate from most of the other example decision sets in Red Hat Decision Manager and is located in ~/rhpam-7.13.5-sources/src/droolsjbpm-integration-USDVERSION/droolsjbpm-integration-examples of the Red Hat Process Automation Manager 7.13.5 Source Distribution from the Red Hat Customer Portal . In Conway's Game of Life, a user interacts with the game by creating an initial configuration or an advanced pattern with defined properties and then observing how the initial state evolves. The objective of the game is to show the development of a population, generation by generation. Each generation results from the preceding one, based on the simultaneous evaluation of all cells. The following basic rules govern what the generation looks like: If a live cell has fewer than two live neighbors, it dies of loneliness. If a live cell has more than three live neighbors, it dies from overcrowding. If a dead cell has exactly three live neighbors, it comes to life. Any cell that does not meet any of those criteria is left as is for the generation. The Conway's Game of Life example uses Red Hat Decision Manager rules with ruleflow-group attributes to define the pattern implemented in the game. The example also contains a version of the decision set that achieves the same behavior using agenda groups. Agenda groups enable you to partition the decision engine agenda to provide execution control over groups of rules. By default, all rules are in the agenda group MAIN . You can use the agenda-group attribute to specify a different agenda group for the rule. This overview does not explore the version of the Conway example using agenda groups. For more information about agenda groups, see the Red Hat Decision Manager example decision sets that specifically address agenda groups. Conway example execution and interaction Similar to other Red Hat Decision Manager decision examples, you execute the Conway ruleflow example by running the org.drools.examples.conway.ConwayRuleFlowGroupRun class as a Java application in your IDE. When you execute the Conway example, the Conway's Game of Life GUI window appears. This window contains an empty grid, or "arena" where the life simulation takes place. Initially the grid is empty because no live cells are in the system yet. Figure 21.24. Conway example GUI after launch Select a predefined pattern from the Pattern drop-down menu and click Generation to click through each population generation. Each cell is either alive or dead, where live cells contain a green ball. As the population evolves from the initial pattern, cells live or die relative to neighboring cells, according to the rules of the game. Figure 21.25. Generation evolution in Conway example Neighbors include not only cells to the left, right, top, and bottom but also cells that are connected diagonally, so that each cell has a total of eight neighbors. Exceptions are the corner cells, which have only three neighbors, and the cells along the four borders, with five neighbors each. You can manually intervene to create or kill cells by clicking the cell. To run through an evolution automatically from the initial pattern, click Start . Conway example rules with ruleflow groups The rules in the ConwayRuleFlowGroupRun example use ruleflow groups to control rule execution. A ruleflow group is a group of rules associated by the ruleflow-group rule attribute. These rules can only fire when the group is activated. The group itself can only become active when the elaboration of the ruleflow diagram reaches the node representing the group. The Conway example uses the following ruleflow groups for rules: "register neighbor" "evaluate" "calculate" "reset calculate" "birth" "kill" "kill all" All of the Cell objects are inserted into the KIE session and the "register ... " rules in the ruleflow group "register neighbor" are allowed to execute by the ruleflow process. This group of four rules creates Neighbor relations between some cell and its northeastern, northern, northwestern, and western neighbors. This relation is bidirectional and handles the other four directions. Border cells do not require any special treatment. These cells are not paired with neighboring cells where there is not any. By the time all activations have fired for these rules, all cells are related to all their neighboring cells. Rules "register ... " After all the cells are inserted, some Java code applies the pattern to the grid, setting certain cells to Live . Then, when the user clicks Start or Generation , the example executes the Generation ruleflow. This ruleflow manages all changes of cells in each generation cycle. Figure 21.26. Generation ruleflow The ruleflow process enters the "evaluate" ruleflow group and any active rules in the group can fire. The rules "Kill the ... " and "Give Birth" in this group apply the game rules to birth or kill cells. The example uses the phase attribute to drive the reasoning of the Cell object by specific groups of rules. Typically, the phase is tied to a ruleflow group in the ruleflow process definition. Notice that the example does not change the state of any Cell objects at this point because it must complete the full evaluation before those changes can be applied. The example sets the cell to a phase that is either Phase.KILL or Phase.BIRTH , which is used later to control actions applied to the Cell object. Rules "Kill the ... " and "Give Birth" After all Cell objects in the grid have been evaluated, the example uses the "reset calculate" rule to clear any activations in the "calculate" ruleflow group. The example then enters a split in the ruleflow that enables the rules "kill" and "birth" to fire, if the ruleflow group is activated. These rules apply the state change. Rules "reset calculate", "kill", and "birth" At this stage, several Cell objects have been modified with the state changed to either LIVE or DEAD . When a cell becomes live or dead, the example uses the Neighbor relation in the rules "Calculate ... " to iterate over all surrounding cells, increasing or decreasing the liveNeighbor count. Any cell that has its count changed is also set to the EVALUATE phase to make sure it is included in the reasoning during the evaluation stage of the ruleflow process. After the live count has been determined and set for all cells, the ruleflow process ends. If the user initially clicked Start , the decision engine restarts the ruleflow at that point. If the user initially clicked Generation , the user can request another generation. Rules "Calculate ... " 21.10. House of Doom example decisions (backward chaining and recursion) The House of Doom example decision set demonstrates how the decision engine uses backward chaining and recursion to reach defined goals or subgoals in a hierarchical system. The following is an overview of the House of Doom example: Name : backwardchaining Main class : org.drools.examples.backwardchaining.HouseOfDoomMain (in src/main/java ) Module : drools-examples Type : Java application Rule file : org.drools.examples.backwardchaining.BC-Example.drl (in src/main/resources ) Objective : Demonstrates backward chaining and recursion A backward-chaining rule system is a goal-driven system that starts with a conclusion that the decision engine attempts to satisfy, often using recursion. If the system cannot reach the conclusion or goal, it searches for subgoals, which are conclusions that complete part of the current goal. The system continues this process until either the initial conclusion is satisfied or all subgoals are satisfied. In contrast, a forward-chaining rule system is a data-driven system that starts with a fact in the working memory of the decision engine and reacts to changes to that fact. When objects are inserted into working memory, any rule conditions that become true as a result of the change are scheduled for execution by the agenda. The decision engine in Red Hat Decision Manager uses both forward and backward chaining to evaluate rules. The following diagram illustrates how the decision engine evaluates rules using forward chaining overall with a backward-chaining segment in the logic flow: Figure 21.27. Rule evaluation logic using forward and backward chaining The House of Doom example uses rules with various types of queries to find the location of rooms and items within the house. The sample class Location.java contains the item and location elements used in the example. The sample class HouseOfDoomMain.java inserts the items or rooms in their respective locations in the house and executes the rules. Items and locations in HouseOfDoomMain.java class ksession.insert( new Location("Office", "House") ); ksession.insert( new Location("Kitchen", "House") ); ksession.insert( new Location("Knife", "Kitchen") ); ksession.insert( new Location("Cheese", "Kitchen") ); ksession.insert( new Location("Desk", "Office") ); ksession.insert( new Location("Chair", "Office") ); ksession.insert( new Location("Computer", "Desk") ); ksession.insert( new Location("Drawer", "Desk") ); The example rules rely on backward chaining and recursion to determine the location of all items and rooms in the house structure. The following diagram illustrates the structure of the House of Doom and the items and rooms within it: Figure 21.28. House of Doom structure To execute the example, run the org.drools.examples.backwardchaining.HouseOfDoomMain class as a Java application in your IDE. After the execution, the following output appears in the IDE console window: Execution output in the IDE console All rules in the example have fired to detect the location of all items in the house and to print the location of each in the output. Recursive query and related rules A recursive query repeatedly searches through the hierarchy of a data structure for relationships between elements. In the House of Doom example, the BC-Example.drl file contains an isContainedIn query that most of the rules in the example use to recursively evaluate the house data structure for data inserted into the decision engine: Recursive query in BC-Example.drl The rule "go" prints every string inserted into the system to determine how items are implemented, and the rule "go1" calls the query isContainedIn : Rules "go" and "go1" The example inserts the "go1" string into the decision engine and activates the "go1" rule to detect that item Office is in the location House : Insert string and fire rules Rule "go1" output in the IDE console Transitive closure rule Transitive closure is a relationship between an element contained in a parent element that is multiple levels higher in a hierarchical structure. The rule "go2" identifies the transitive closure relationship of the Drawer and the House : The Drawer is in the Desk in the Office in the House . The example inserts the "go2" string into the decision engine and activates the "go2" rule to detect that item Drawer is ultimately within the location House : Insert string and fire rules Rule "go2" output in the IDE console The decision engine determines this outcome based on the following logic: The query recursively searches through several levels in the house to detect the transitive closure between Drawer and House . Instead of using Location( x, y; ) , the query uses the value of (z, y; ) because Drawer is not directly in House . The z argument is currently unbound, which means it has no value and returns everything that is in the argument. The y argument is currently bound to House , so z returns Office and Kitchen . The query gathers information from the Office and checks recursively if the Drawer is in the Office . The query line isContainedIn( x, z; ) is called for these parameters. No instance of Drawer exists directly in Office , so no match is found. With z unbound, the query returns data within the Office and determines that z == Desk . The isContainedIn query recursively searches three times, and on the third time, the query detects an instance of Drawer in Desk . After this match on the first location, the query recursively searches back up the structure to determine that the Drawer is in the Desk , the Desk is in the Office , and the Office is in the House . Therefore, the Drawer is in the House and the rule is satisfied. Reactive query rule A reactive query searches through the hierarchy of a data structure for relationships between elements and is dynamically updated when elements in the structure are modified. The rule "go3" functions as a reactive query that detects if a new item Key ever becomes present in the Office by transitive closure: A Key in the Drawer in the Office . Rule "go3" The example inserts the "go3" string into the decision engine and activates the "go3" rule. Initially, this rule is not satisfied because no item Key exists in the house structure, so the rule produces no output. Insert string and fire rules Rule "go3" output in the IDE console (unsatisfied) The example then inserts a new item Key in the location Drawer , which is in Office . This change satisfies the transitive closure in the "go3" rule and the output is populated accordingly. Insert new item location and fire rules Rule "go3" output in the IDE console (satisfied) This change also adds another level in the structure that the query includes in subsequent recursive searches. Queries with unbound arguments in rules A query with one or more unbound arguments returns all undefined (unbound) items within a defined (bound) argument of the query. If all arguments in a query are unbound, then the query returns all items within the scope of the query. The rule "go4" uses an unbound argument thing to search for all items within the bound argument Office , instead of using a bound argument to search for a specific item in the Office : Rule "go4" The example inserts the "go4" string into the decision engine and activates the "go4" rule to return all items in the Office : Insert string and fire rules Rule "go4" output in the IDE console The rule "go5" uses both unbound arguments thing and location to search for all items and their locations in the entire House data structure: Rule "go5" The example inserts the "go5" string into the decision engine and activates the "go5" rule to return all items and their locations in the House data structure: Insert string and fire rules Rule "go5" output in the IDE console

Commands:
KieServices ks = KieServices.Factory.get(); 1 KieContainer kc = ks.getKieClasspathContainer(); 2 KieSession ksession = kc.newKieSession("HelloWorldKS"); 3
// Set up listeners. ksession.addEventListener( new DebugAgendaEventListener() ); ksession.addEventListener( new DebugRuleRuntimeEventListener() ); // Set up a file-based audit logger. KieRuntimeLogger logger = KieServices.get().getLoggers().newFileLogger( ksession, "./target/helloworld" ); // Set up a ThreadedFileLogger so that the audit view reflects events while debugging. KieRuntimeLogger logger = ks.getLoggers().newThreadedFileLogger( ksession, "./target/helloworld", 1000 );
// Insert facts into the KIE session. final Message message = new Message(); message.setMessage( "Hello World" ); message.setStatus( Message.HELLO ); ksession.insert( message ); // Fire the rules. ksession.fireAllRules();
public static class Message { public static final int HELLO = 0; public static final int GOODBYE = 1; private String message; private int status; }
rule "Hello World" when m : Message( status == Message.HELLO, message : message ) then System.out.println( message ); modify ( m ) { message = "Goodbye cruel world", status = Message.GOODBYE }; end
rule "Good Bye" when Message( status == Message.GOODBYE, message : message ) then System.out.println( message ); end
Hello World Goodbye cruel world
==>[ActivationCreated(0): rule=Hello World; tuple=[fid:1:1:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]] [ObjectInserted: handle=[fid:1:1:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]; object=org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96] [BeforeActivationFired: rule=Hello World; tuple=[fid:1:1:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]] ==>[ActivationCreated(4): rule=Good Bye; tuple=[fid:1:2:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]] [ObjectUpdated: handle=[fid:1:2:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]; old_object=org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96; new_object=org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96] [AfterActivationFired(0): rule=Hello World] [BeforeActivationFired: rule=Good Bye; tuple=[fid:1:2:org.drools.examples.helloworld.HelloWorldExampleUSDMessage@17cec96]] [AfterActivationFired(4): rule=Good Bye]
public class State { public static final int NOTRUN = 0; public static final int FINISHED = 1; private final PropertyChangeSupport changes = new PropertyChangeSupport( this ); private String name; private int state; ... setters and getters go here }
final State a = new State( "A" ); final State b = new State( "B" ); final State c = new State( "C" ); final State d = new State( "D" ); ksession.insert( a ); ksession.insert( b ); ksession.insert( c ); ksession.insert( d ); ksession.fireAllRules(); // Dispose KIE session if stateful (not required if stateless). ksession.dispose();
A finished B finished C finished D finished
rule "Bootstrap" when a : State(name == "A", state == State.NOTRUN ) then System.out.println(a.getName() + " finished" ); a.setState( State.FINISHED ); end
rule "A to B" when State(name == "A", state == State.FINISHED ) b : State(name == "B", state == State.NOTRUN ) then System.out.println(b.getName() + " finished" ); b.setState( State.FINISHED ); end
rule "B to C" salience 10 when State(name == "B", state == State.FINISHED ) c : State(name == "C", state == State.NOTRUN ) then System.out.println(c.getName() + " finished" ); c.setState( State.FINISHED ); end rule "B to D" when State(name == "B", state == State.FINISHED ) d : State(name == "D", state == State.NOTRUN ) then System.out.println(d.getName() + " finished" ); d.setState( State.FINISHED ); end
rule "B to C" agenda-group "B to C" auto-focus true when State(name == "B", state == State.FINISHED ) c : State(name == "C", state == State.NOTRUN ) then System.out.println(c.getName() + " finished" ); c.setState( State.FINISHED ); kcontext.getKnowledgeRuntime().getAgenda().getAgendaGroup( "B to D" ).setFocus(); end
rule "B to D" agenda-group "B to D" when State(name == "B", state == State.FINISHED ) d : State(name == "D", state == State.NOTRUN ) then System.out.println(d.getName() + " finished" ); d.setState( State.FINISHED ); end
A finished B finished C finished D finished
declare type State @propertyChangeSupport end
public void setState(final int newState) { int oldState = this.state; this.state = newState; this.changes.firePropertyChange( "state", oldState, newState ); }
public static class Fibonacci { private int sequence; private long value; public Fibonacci( final int sequence ) { this.sequence = sequence; this.value = -1; } ... setters and getters go here }
recurse for 50 recurse for 49 recurse for 48 recurse for 47 recurse for 5 recurse for 4 recurse for 3 recurse for 2 1 == 1 2 == 1 3 == 2 4 == 3 5 == 5 6 == 8 47 == 2971215073 48 == 4807526976 49 == 7778742049 50 == 12586269025
ksession.insert( new Fibonacci( 50 ) ); ksession.fireAllRules();
rule "Recurse" salience 10 when f : Fibonacci ( value == -1 ) not ( Fibonacci ( sequence == 1 ) ) then insert( new Fibonacci( f.sequence - 1 ) ); System.out.println( "recurse for " + f.sequence ); end
rule "Bootstrap" when f : Fibonacci( sequence == 1 || == 2, value == -1 ) // multi-restriction then modify ( f ){ value = 1 }; System.out.println( f.sequence + " == " + f.value ); end
rule "Calculate" when // Bind f1 and s1. f1 : Fibonacci( s1 : sequence, value != -1 ) // Bind f2 and v2, refer to bound variable s1. f2 : Fibonacci( sequence == (s1 + 1), v2 : value != -1 ) // Bind f3 and s3, alternative reference of f2.sequence. f3 : Fibonacci( s3 : sequence == (f2.sequence + 1 ), value == -1 ) then // Note the various referencing techniques. modify ( f3 ) { value = f1.value + v2 }; System.out.println( s3 + " == " + f3.value ); end
Cheapest possible BASE PRICE IS: 120 DISCOUNT IS: 20
template header age[] profile priorClaims policyType base reason package org.drools.examples.decisiontable; template "Pricing bracket" age policyType base rule "Pricing bracket_@{row.rowNumber}" when Driver(age >= @{age0}, age <= @{age1} , priorClaims == "@{priorClaims}" , locationRiskProfile == "@{profile}" ) policy: Policy(type == "@{policyType}") then policy.setBasePrice(@{base}); System.out.println("@{reason}"); end end template
template header age[] priorClaims policyType discount package org.drools.examples.decisiontable; template "discounts" age priorClaims policyType discount rule "Discounts_@{row.rowNumber}" when Driver(age >= @{age0}, age <= @{age1}, priorClaims == "@{priorClaims}") policy: Policy(type == "@{policyType}") then policy.applyDiscount(@{discount}); end end template
<kbase name="DecisionTableKB" packages="org.drools.examples.decisiontable"> <ksession name="DecisionTableKS" type="stateless"/> </kbase> <kbase name="DTableWithTemplateKB" packages="org.drools.examples.decisiontable-template"> <ruleTemplate dtable="org/drools/examples/decisiontable-template/ExamplePolicyPricingTemplateData.xls" template="org/drools/examples/decisiontable-template/BasePricing.drt" row="3" col="3"/> <ruleTemplate dtable="org/drools/examples/decisiontable-template/ExamplePolicyPricingTemplateData.xls" template="org/drools/examples/decisiontable-template/PromotionalPricing.drt" row="18" col="3"/> <ksession name="DTableWithTemplateKS"/> </kbase>
DecisionTableConfiguration dtableconfiguration = KnowledgeBuilderFactory.newDecisionTableConfiguration(); dtableconfiguration.setInputType( DecisionTableInputType.XLS ); KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); Resource xlsRes = ResourceFactory.newClassPathResource( "ExamplePolicyPricing.xls", getClass() ); kbuilder.add( xlsRes, ResourceType.DTABLE, dtableconfiguration );
// KieServices is the factory for all KIE services. KieServices ks = KieServices.Factory.get(); // Create a KIE container on the class path. KieContainer kc = ks.getKieClasspathContainer(); // Create the stock. Vector<Product> stock = new Vector<Product>(); stock.add( new Product( "Gold Fish", 5 ) ); stock.add( new Product( "Fish Tank", 25 ) ); stock.add( new Product( "Fish Food", 2 ) ); // A callback is responsible for populating the working memory and for firing all rules. PetStoreUI ui = new PetStoreUI( stock, new CheckoutCallback( kc ) ); ui.createAndShowGUI();
public String checkout(JFrame frame, List<Product> items) { Order order = new Order(); // Iterate through list and add to cart. for ( Product p: items ) { order.addItem( new Purchase( order, p ) ); } // Add the JFrame to the ApplicationData to allow for user interaction. // From the KIE container, a KIE session is created based on // its definition and configuration in the META-INF/kmodule.xml file. KieSession ksession = kcontainer.newKieSession("PetStoreKS"); ksession.setGlobal( "frame", frame ); ksession.setGlobal( "textArea", this.output ); ksession.insert( new Product( "Gold Fish", 5 ) ); ksession.insert( new Product( "Fish Tank", 25 ) ); ksession.insert( new Product( "Fish Food", 2 ) ); ksession.insert( new Product( "Fish Food Sample", 0 ) ); ksession.insert( order ); // Execute rules. ksession.fireAllRules(); // Return the state of the cart return order.toString(); }
package org.drools.examples; import org.kie.api.runtime.KieRuntime; import org.drools.examples.petstore.PetStoreExample.Order; import org.drools.examples.petstore.PetStoreExample.Purchase; import org.drools.examples.petstore.PetStoreExample.Product; import java.util.ArrayList; import javax.swing.JOptionPane; import javax.swing.JFrame; global JFrame frame global javax.swing.JTextArea textArea
function void doCheckout(JFrame frame, KieRuntime krt) { Object[] options = {"Yes", "No"}; int n = JOptionPane.showOptionDialog(frame, "Would you like to checkout?", "", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]); if (n == 0) { krt.getAgenda().getAgendaGroup( "checkout" ).setFocus(); } } function boolean requireTank(JFrame frame, KieRuntime krt, Order order, Product fishTank, int total) { Object[] options = {"Yes", "No"}; int n = JOptionPane.showOptionDialog(frame, "Would you like to buy a tank for your " + total + " fish?", "Purchase Suggestion", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]); System.out.print( "SUGGESTION: Would you like to buy a tank for your " + total + " fish? - " ); if (n == 0) { Purchase purchase = new Purchase( order, fishTank ); krt.insert( purchase ); order.addItem( purchase ); System.out.println( "Yes" ); } else { System.out.println( "No" ); } return true; }
// Insert each item in the shopping cart into the working memory. rule "Explode Cart" agenda-group "init" auto-focus true salience 10 when USDorder : Order( grossTotal == -1 ) USDitem : Purchase() from USDorder.items then insert( USDitem ); kcontext.getKnowledgeRuntime().getAgenda().getAgendaGroup( "show items" ).setFocus(); kcontext.getKnowledgeRuntime().getAgenda().getAgendaGroup( "evaluate" ).setFocus(); end
rule "Show Items" agenda-group "show items" when USDorder : Order() USDp : Purchase( order == USDorder ) then textArea.append( USDp.product + "\n"); end
// Free fish food sample when users buy a goldfish if they did not already buy // fish food and do not already have a fish food sample. rule "Free Fish Food Sample" agenda-group "evaluate" 1 when USDorder : Order() not ( USDp : Product( name == "Fish Food") && Purchase( product == USDp ) ) 2 not ( USDp : Product( name == "Fish Food Sample") && Purchase( product == USDp ) ) 3 exists ( USDp : Product( name == "Gold Fish") && Purchase( product == USDp ) ) 4 USDfishFoodSample : Product( name == "Fish Food Sample" ); then System.out.println( "Adding free Fish Food Sample to cart" ); purchase = new Purchase(USDorder, USDfishFoodSample); insert( purchase ); USDorder.addItem( purchase ); end
// Suggest a fish tank if users buy more than five goldfish and // do not already have a tank. rule "Suggest Tank" agenda-group "evaluate" when USDorder : Order() not ( USDp : Product( name == "Fish Tank") && Purchase( product == USDp ) ) 1 ArrayList( USDtotal : size > 5 ) from collect( Purchase( product.name == "Gold Fish" ) ) 2 USDfishTank : Product( name == "Fish Tank" ) then requireTank(frame, kcontext.getKieRuntime(), USDorder, USDfishTank, USDtotal); end
rule "do checkout" when then doCheckout(frame, kcontext.getKieRuntime()); end
rule "Gross Total" agenda-group "checkout" when USDorder : Order( grossTotal == -1) Number( total : doubleValue ) from accumulate( Purchase( USDprice : product.price ), sum( USDprice ) ) then modify( USDorder ) { grossTotal = total } textArea.append( "\ngross total=" + total + "\n" ); end rule "Apply 5% Discount" agenda-group "checkout" when USDorder : Order( grossTotal >= 10 && < 20 ) then USDorder.discountedTotal = USDorder.grossTotal * 0.95; textArea.append( "discountedTotal total=" + USDorder.discountedTotal + "\n" ); end rule "Apply 10% Discount" agenda-group "checkout" when USDorder : Order( grossTotal >= 20 ) then USDorder.discountedTotal = USDorder.grossTotal * 0.90; textArea.append( "discountedTotal total=" + USDorder.discountedTotal + "\n" ); end
Adding free Fish Food Sample to cart SUGGESTION: Would you like to buy a tank for your 6 fish? - Yes
public class Politician { private String name; private boolean honest; }
public class Hope { public Hope() { } }
rule "We have an honest Politician" salience 10 when exists( Politician( honest == true ) ) then insertLogical( new Hope() ); end
rule "Hope Lives" salience 10 when exists( Hope() ) then System.out.println("Hurrah!!! Democracy Lives"); end
rule "Corrupt the Honest" when politician : Politician( honest == true ) exists( Hope() ) then System.out.println( "I'm an evil corporation and I have corrupted " + politician.getName() ); modify ( politician ) { honest = false }; end
rule "Hope is Dead" when not( Hope() ) then System.out.println( "We are all Doomed!!! Democracy is Dead" ); end
public static void execute( KieContainer kc ) { KieSession ksession = kc.newKieSession("HonestPoliticianKS"); final Politician p1 = new Politician( "President of Umpa Lumpa", true ); final Politician p2 = new Politician( "Prime Minster of Cheeseland", true ); final Politician p3 = new Politician( "Tsar of Pringapopaloo", true ); final Politician p4 = new Politician( "Omnipotence Om", true ); ksession.insert( p1 ); ksession.insert( p2 ); ksession.insert( p3 ); ksession.insert( p4 ); ksession.fireAllRules(); ksession.dispose(); }
Hurrah!!! Democracy Lives I'm an evil corporation and I have corrupted President of Umpa Lumpa I'm an evil corporation and I have corrupted Prime Minster of Cheeseland I'm an evil corporation and I have corrupted Tsar of Pringapopaloo I'm an evil corporation and I have corrupted Omnipotence Om We are all Doomed!!! Democracy is Dead
package org.drools.examples.honestpolitician; import org.kie.api.KieServices; import org.kie.api.event.rule.DebugAgendaEventListener; 1 import org.kie.api.event.rule.DebugRuleRuntimeEventListener; import org.kie.api.runtime.KieContainer; import org.kie.api.runtime.KieSession; public class HonestPoliticianExample { /** * @param args */ public static void main(final String[] args) { KieServices ks = KieServices.Factory.get(); 2 //ks = KieServices.Factory.get(); KieContainer kc = KieServices.Factory.get().getKieClasspathContainer(); System.out.println(kc.verify().getMessages().toString()); //execute( kc ); execute( ks, kc); 3 } public static void execute( KieServices ks, KieContainer kc ) { 4 KieSession ksession = kc.newKieSession("HonestPoliticianKS"); final Politician p1 = new Politician( "President of Umpa Lumpa", true ); final Politician p2 = new Politician( "Prime Minster of Cheeseland", true ); final Politician p3 = new Politician( "Tsar of Pringapopaloo", true ); final Politician p4 = new Politician( "Omnipotence Om", true ); ksession.insert( p1 ); ksession.insert( p2 ); ksession.insert( p3 ); ksession.insert( p4 ); // The application can also setup listeners 5 ksession.addEventListener( new DebugAgendaEventListener() ); ksession.addEventListener( new DebugRuleRuntimeEventListener() ); // Set up a file-based audit logger. ks.getLoggers().newFileLogger( ksession, "./target/honestpolitician" ); 6 ksession.fireAllRules(); ksession.dispose(); } }
single 8 at [0,1] column elimination due to [1,2]: remove 9 from [4,2] hidden single 9 at [1,2] row elimination due to [2,8]: remove 7 from [2,4] remove 6 from [3,8] due to naked pair at [3,2] and [3,7] hidden pair in row at [4,6] and [4,4]
Col: 0 Col: 1 Col: 2 Col: 3 Col: 4 Col: 5 Col: 6 Col: 7 Col: 8 Row 0: 123456789 --- 5 --- --- 6 --- --- 8 --- 123456789 --- 1 --- --- 9 --- --- 4 --- 123456789 Row 1: --- 9 --- 123456789 123456789 --- 6 --- 123456789 --- 5 --- 123456789 123456789 --- 3 --- Row 2: --- 7 --- 123456789 123456789 --- 4 --- --- 9 --- --- 3 --- 123456789 123456789 --- 8 --- Row 3: --- 8 --- --- 9 --- --- 7 --- 123456789 --- 4 --- 123456789 --- 6 --- --- 3 --- --- 5 --- Row 4: 123456789 123456789 --- 3 --- --- 9 --- 123456789 --- 6 --- --- 8 --- 123456789 123456789 Row 5: --- 4 --- --- 6 --- --- 5 --- 123456789 --- 8 --- 123456789 --- 2 --- --- 9 --- --- 1 --- Row 6: --- 5 --- 123456789 123456789 --- 2 --- --- 6 --- --- 9 --- 123456789 123456789 --- 7 --- Row 7: --- 6 --- 123456789 123456789 --- 5 --- 123456789 --- 4 --- 123456789 123456789 --- 9 --- Row 8: 123456789 --- 4 --- --- 9 --- --- 7 --- 123456789 --- 8 --- --- 3 --- --- 5 --- 123456789
cell [0,8]: 5 has a duplicate in row 0 cell [0,0]: 5 has a duplicate in row 0 cell [6,0]: 8 has a duplicate in col 0 cell [4,0]: 8 has a duplicate in col 0 Validation complete.
Validation complete. Sorry - can't solve this grid.
rule "duplicate in cell row" when USDc: Cell( USDv: value != null ) USDcr: CellRow( cells contains USDc ) exists Cell( this != USDc, value == USDv, cellRow == USDcr ) then System.out.println( "cell " + USDc.toString() + " has a duplicate in row " + USDcr.getNumber() ); end rule "duplicate in cell col" when USDc: Cell( USDv: value != null ) USDcc: CellCol( cells contains USDc ) exists Cell( this != USDc, value == USDv, cellCol == USDcc ) then System.out.println( "cell " + USDc.toString() + " has a duplicate in col " + USDcc.getNumber() ); end rule "duplicate in cell sqr" when USDc: Cell( USDv: value != null ) USDcs: CellSqr( cells contains USDc ) exists Cell( this != USDc, value == USDv, cellSqr == USDcs ) then System.out.println( "cell " + USDc.toString() + " has duplicate in its square of nine." ); end
rule "terminate group" salience -100 when then System.out.println( "Validation complete." ); drools.halt(); end
// A Setting object is inserted to define the value of a Cell. // Rule for updating the cell and all cell groups that contain it rule "set a value" when // A Setting with row and column number, and a value USDs: Setting( USDrn: rowNo, USDcn: colNo, USDv: value ) // A matching Cell, with no value set USDc: Cell( rowNo == USDrn, colNo == USDcn, value == null, USDcr: cellRow, USDcc: cellCol, USDcs: cellSqr ) // Count down USDctr: Counter( USDcount: count ) then // Modify the Cell by setting its value. modify( USDc ){ setValue( USDv ) } // System.out.println( "set cell " + USDc.toString() ); modify( USDcr ){ blockValue( USDv ) } modify( USDcc ){ blockValue( USDv ) } modify( USDcs ){ blockValue( USDv ) } modify( USDctr ){ setCount( USDcount - 1 ) } end // Rule for removing a value from all cells that are siblings // in one of the three cell groups rule "eliminate a value from Cell" when // A Setting with row and column number, and a value USDs: Setting( USDrn: rowNo, USDcn: colNo, USDv: value ) // The matching Cell, with the value already set Cell( rowNo == USDrn, colNo == USDcn, value == USDv, USDexCells: exCells ) // For all Cells that are associated with the updated cell USDc: Cell( free contains USDv ) from USDexCells then // System.out.println( "clear " + USDv + " from cell " + USDc.posAsString() ); // Modify a related Cell by blocking the assigned value. modify( USDc ){ blockValue( USDv ) } end // Rule for eliminating the Setting fact rule "retract setting" when // A Setting with row and column number, and a value USDs: Setting( USDrn: rowNo, USDcn: colNo, USDv: value ) // The matching Cell, with the value already set USDc: Cell( rowNo == USDrn, colNo == USDcn, value == USDv ) // This is the negation of the last pattern in the previous rule. // Now the Setting fact can be safely retracted. not( USDx: Cell( free contains USDv ) and Cell( this == USDc, exCells contains USDx ) ) then // System.out.println( "done setting cell " + USDc.toString() ); // Discard the Setter fact. delete( USDs ); // Sudoku.sudoku.consistencyCheck(); end
// Detect a set of candidate values with cardinality 1 for some Cell. // This is the value to be set. rule "single" when // Currently no setting underway not Setting() // One element in the "free" set USDc: Cell( USDrn: rowNo, USDcn: colNo, freeCount == 1 ) then Integer i = USDc.getFreeValue(); if (explain) System.out.println( "single " + i + " at " + USDc.posAsString() ); // Insert another Setter fact. insert( new Setting( USDrn, USDcn, i ) ); end // Detect a set of candidate values with a value that is the only one // in one of its groups. This is the value to be set. rule "hidden single" when // Currently no setting underway not Setting() not Cell( freeCount == 1 ) // Some integer USDi: Integer() // The "free" set contains this number USDc: Cell( USDrn: rowNo, USDcn: colNo, freeCount > 1, free contains USDi ) // A cell group contains this cell USDc. USDcg: CellGroup( cells contains USDc ) // No other cell from that group contains USDi. not ( Cell( this != USDc, free contains USDi ) from USDcg.getCells() ) then if (explain) System.out.println( "hidden single " + USDi + " at " + USDc.posAsString() ); // Insert another Setter fact. insert( new Setting( USDrn, USDcn, USDi ) ); end
// A "naked pair" is two cells in some cell group with their sets of // permissible values being equal with cardinality 2. These two values // can be removed from all other candidate lists in the group. rule "naked pair" when // Currently no setting underway not Setting() not Cell( freeCount == 1 ) // One cell with two candidates USDc1: Cell( freeCount == 2, USDf1: free, USDr1: cellRow, USDrn1: rowNo, USDcn1: colNo, USDb1: cellSqr ) // The containing cell group USDcg: CellGroup( freeCount > 2, cells contains USDc1 ) // Another cell with two candidates, not the one we already have USDc2: Cell( this != USDc1, free == USDf1 /*** , rowNo >= USDrn1, colNo >= USDcn1 ***/ ) from USDcg.cells // Get one of the "naked pair". Integer( USDv: intValue ) from USDc1.getFree() // Get some other cell with a candidate equal to one from the pair. USDc3: Cell( this != USDc1 && != USDc2, freeCount > 1, free contains USDv ) from USDcg.cells then if (explain) System.out.println( "remove " + USDv + " from " + USDc3.posAsString() + " due to naked pair at " + USDc1.posAsString() + " and " + USDc2.posAsString() ); // Remove the value. modify( USDc3 ){ blockValue( USDv ) } end
// If two cells within the same cell group contain candidate sets with more than // two values, with two values being in both of them but in none of the other // cells, then we have a "hidden pair". We can remove all other candidates from // these two cells. rule "hidden pair in row" when // Currently no setting underway not Setting() not Cell( freeCount == 1 ) // Establish a pair of Integer facts. USDi1: Integer() USDi2: Integer( this > USDi1 ) // Look for a Cell with these two among its candidates. (The upper bound on // the number of candidates avoids a lot of useless work during startup.) USDc1: Cell( USDrn1: rowNo, USDcn1: colNo, freeCount > 2 && < 9, free contains USDi1 && contains USDi2, USDcellRow: cellRow ) // Get another one from the same row, with the same pair among its candidates. USDc2: Cell( this != USDc1, cellRow == USDcellRow, freeCount > 2, free contains USDi1 && contains USDi2 ) // Ascertain that no other cell in the group has one of these two values. not( Cell( this != USDc1 && != USDc2, free contains USDi1 || contains USDi2 ) from USDcellRow.getCells() ) then if( explain) System.out.println( "hidden pair in row at " + USDc1.posAsString() + " and " + USDc2.posAsString() ); // Set the candidate lists of these two Cells to the "hidden pair". modify( USDc1 ){ blockExcept( USDi1, USDi2 ) } modify( USDc2 ){ blockExcept( USDi1, USDi2 ) } end rule "hidden pair in column" when not Setting() not Cell( freeCount == 1 ) USDi1: Integer() USDi2: Integer( this > USDi1 ) USDc1: Cell( USDrn1: rowNo, USDcn1: colNo, freeCount > 2 && < 9, free contains USDi1 && contains USDi2, USDcellCol: cellCol ) USDc2: Cell( this != USDc1, cellCol == USDcellCol, freeCount > 2, free contains USDi1 && contains USDi2 ) not( Cell( this != USDc1 && != USDc2, free contains USDi1 || contains USDi2 ) from USDcellCol.getCells() ) then if (explain) System.out.println( "hidden pair in column at " + USDc1.posAsString() + " and " + USDc2.posAsString() ); modify( USDc1 ){ blockExcept( USDi1, USDi2 ) } modify( USDc2 ){ blockExcept( USDi1, USDi2 ) } end rule "hidden pair in square" when not Setting() not Cell( freeCount == 1 ) USDi1: Integer() USDi2: Integer( this > USDi1 ) USDc1: Cell( USDrn1: rowNo, USDcn1: colNo, freeCount > 2 && < 9, free contains USDi1 && contains USDi2, USDcellSqr: cellSqr ) USDc2: Cell( this != USDc1, cellSqr == USDcellSqr, freeCount > 2, free contains USDi1 && contains USDi2 ) not( Cell( this != USDc1 && != USDc2, free contains USDi1 || contains USDi2 ) from USDcellSqr.getCells() ) then if (explain) System.out.println( "hidden pair in square " + USDc1.posAsString() + " and " + USDc2.posAsString() ); modify( USDc1 ){ blockExcept( USDi1, USDi2 ) } modify( USDc2 ){ blockExcept( USDi1, USDi2 ) } end
rule "X-wings in rows" when not Setting() not Cell( freeCount == 1 ) USDi: Integer() USDca1: Cell( freeCount > 1, free contains USDi, USDra: cellRow, USDrano: rowNo, USDc1: cellCol, USDc1no: colNo ) USDcb1: Cell( freeCount > 1, free contains USDi, USDrb: cellRow, USDrbno: rowNo > USDrano, cellCol == USDc1 ) not( Cell( this != USDca1 && != USDcb1, free contains USDi ) from USDc1.getCells() ) USDca2: Cell( freeCount > 1, free contains USDi, cellRow == USDra, USDc2: cellCol, USDc2no: colNo > USDc1no ) USDcb2: Cell( freeCount > 1, free contains USDi, cellRow == USDrb, cellCol == USDc2 ) not( Cell( this != USDca2 && != USDcb2, free contains USDi ) from USDc2.getCells() ) USDcx: Cell( rowNo == USDrano || == USDrbno, colNo != USDc1no && != USDc2no, freeCount > 1, free contains USDi ) then if (explain) { System.out.println( "X-wing with " + USDi + " in rows " + USDca1.posAsString() + " - " + USDcb1.posAsString() + USDca2.posAsString() + " - " + USDcb2.posAsString() + ", remove from " + USDcx.posAsString() ); } modify( USDcx ){ blockValue( USDi ) } end rule "X-wings in columns" when not Setting() not Cell( freeCount == 1 ) USDi: Integer() USDca1: Cell( freeCount > 1, free contains USDi, USDc1: cellCol, USDc1no: colNo, USDra: cellRow, USDrano: rowNo ) USDca2: Cell( freeCount > 1, free contains USDi, USDc2: cellCol, USDc2no: colNo > USDc1no, cellRow == USDra ) not( Cell( this != USDca1 && != USDca2, free contains USDi ) from USDra.getCells() ) USDcb1: Cell( freeCount > 1, free contains USDi, cellCol == USDc1, USDrb: cellRow, USDrbno: rowNo > USDrano ) USDcb2: Cell( freeCount > 1, free contains USDi, cellCol == USDc2, cellRow == USDrb ) not( Cell( this != USDcb1 && != USDcb2, free contains USDi ) from USDrb.getCells() ) USDcx: Cell( colNo == USDc1no || == USDc2no, rowNo != USDrano && != USDrbno, freeCount > 1, free contains USDi ) then if (explain) { System.out.println( "X-wing with " + USDi + " in columns " + USDca1.posAsString() + " - " + USDca2.posAsString() + USDcb1.posAsString() + " - " + USDcb2.posAsString() + ", remove from " + USDcx.posAsString() ); } modify( USDcx ){ blockValue( USDi ) } end
rule "intersection removal column" when not Setting() not Cell( freeCount == 1 ) USDi: Integer() // Occurs in a Cell USDc: Cell( free contains USDi, USDcs: cellSqr, USDcc: cellCol ) // Does not occur in another cell of the same square and a different column not Cell( this != USDc, free contains USDi, cellSqr == USDcs, cellCol != USDcc ) // A cell exists in the same column and another square containing this value. USDcx: Cell( freeCount > 1, free contains USDi, cellCol == USDcc, cellSqr != USDcs ) then // Remove the value from that other cell. if (explain) { System.out.println( "column elimination due to " + USDc.posAsString() + ": remove " + USDi + " from " + USDcx.posAsString() ); } modify( USDcx ){ blockValue( USDi ) } end rule "intersection removal row" when not Setting() not Cell( freeCount == 1 ) USDi: Integer() // Occurs in a Cell USDc: Cell( free contains USDi, USDcs: cellSqr, USDcr: cellRow ) // Does not occur in another cell of the same square and a different row. not Cell( this != USDc, free contains USDi, cellSqr == USDcs, cellRow != USDcr ) // A cell exists in the same row and another square containing this value. USDcx: Cell( freeCount > 1, free contains USDi, cellRow == USDcr, cellSqr != USDcs ) then // Remove the value from that other cell. if (explain) { System.out.println( "row elimination due to " + USDc.posAsString() + ": remove " + USDi + " from " + USDcx.posAsString() ); } modify( USDcx ){ blockValue( USDi ) } end
rule "register north east" ruleflow-group "register neighbor" when USDcell: Cell( USDrow : row, USDcol : col ) USDnorthEast : Cell( row == (USDrow - 1), col == ( USDcol + 1 ) ) then insert( new Neighbor( USDcell, USDnorthEast ) ); insert( new Neighbor( USDnorthEast, USDcell ) ); end rule "register north" ruleflow-group "register neighbor" when USDcell: Cell( USDrow : row, USDcol : col ) USDnorth : Cell( row == (USDrow - 1), col == USDcol ) then insert( new Neighbor( USDcell, USDnorth ) ); insert( new Neighbor( USDnorth, USDcell ) ); end rule "register north west" ruleflow-group "register neighbor" when USDcell: Cell( USDrow : row, USDcol : col ) USDnorthWest : Cell( row == (USDrow - 1), col == ( USDcol - 1 ) ) then insert( new Neighbor( USDcell, USDnorthWest ) ); insert( new Neighbor( USDnorthWest, USDcell ) ); end rule "register west" ruleflow-group "register neighbor" when USDcell: Cell( USDrow : row, USDcol : col ) USDwest : Cell( row == USDrow, col == ( USDcol - 1 ) ) then insert( new Neighbor( USDcell, USDwest ) ); insert( new Neighbor( USDwest, USDcell ) ); end
rule "Kill The Lonely" ruleflow-group "evaluate" no-loop when // A live cell has fewer than 2 live neighbors. theCell: Cell( liveNeighbors < 2, cellState == CellState.LIVE, phase == Phase.EVALUATE ) then modify( theCell ){ setPhase( Phase.KILL ); } end rule "Kill The Overcrowded" ruleflow-group "evaluate" no-loop when // A live cell has more than 3 live neighbors. theCell: Cell( liveNeighbors > 3, cellState == CellState.LIVE, phase == Phase.EVALUATE ) then modify( theCell ){ setPhase( Phase.KILL ); } end rule "Give Birth" ruleflow-group "evaluate" no-loop when // A dead cell has 3 live neighbors. theCell: Cell( liveNeighbors == 3, cellState == CellState.DEAD, phase == Phase.EVALUATE ) then modify( theCell ){ theCell.setPhase( Phase.BIRTH ); } end
rule "reset calculate" ruleflow-group "reset calculate" when then WorkingMemory wm = drools.getWorkingMemory(); wm.clearRuleFlowGroup( "calculate" ); end rule "kill" ruleflow-group "kill" no-loop when theCell: Cell( phase == Phase.KILL ) then modify( theCell ){ setCellState( CellState.DEAD ), setPhase( Phase.DONE ); } end rule "birth" ruleflow-group "birth" no-loop when theCell: Cell( phase == Phase.BIRTH ) then modify( theCell ){ setCellState( CellState.LIVE ), setPhase( Phase.DONE ); } end
rule "Calculate Live" ruleflow-group "calculate" lock-on-active when theCell: Cell( cellState == CellState.LIVE ) Neighbor( cell == theCell, USDneighbor : neighbor ) then modify( USDneighbor ){ setLiveNeighbors( USDneighbor.getLiveNeighbors() + 1 ), setPhase( Phase.EVALUATE ); } end rule "Calculate Dead" ruleflow-group "calculate" lock-on-active when theCell: Cell( cellState == CellState.DEAD ) Neighbor( cell == theCell, USDneighbor : neighbor ) then modify( USDneighbor ){ setLiveNeighbors( USDneighbor.getLiveNeighbors() - 1 ), setPhase( Phase.EVALUATE ); } end
ksession.insert( new Location("Office", "House") ); ksession.insert( new Location("Kitchen", "House") ); ksession.insert( new Location("Knife", "Kitchen") ); ksession.insert( new Location("Cheese", "Kitchen") ); ksession.insert( new Location("Desk", "Office") ); ksession.insert( new Location("Chair", "Office") ); ksession.insert( new Location("Computer", "Desk") ); ksession.insert( new Location("Drawer", "Desk") );
go1 Office is in the House --- go2 Drawer is in the House --- go3 --- Key is in the Office --- go4 Chair is in the Office Desk is in the Office Key is in the Office Computer is in the Office Drawer is in the Office --- go5 Chair is in Office Desk is in Office Drawer is in Desk Key is in Drawer Kitchen is in House Cheese is in Kitchen Knife is in Kitchen Computer is in Desk Office is in House Key is in Office Drawer is in House Computer is in House Key is in House Desk is in House Chair is in House Knife is in House Cheese is in House Computer is in Office Drawer is in Office Key is in Desk
query isContainedIn( String x, String y ) Location( x, y; ) or ( Location( z, y; ) and isContainedIn( x, z; ) ) end
rule "go" salience 10 when USDs : String() then System.out.println( USDs ); end rule "go1" when String( this == "go1" ) isContainedIn("Office", "House"; ) then System.out.println( "Office is in the House" ); end
ksession.insert( "go1" ); ksession.fireAllRules();
go1 Office is in the House
rule "go2" when String( this == "go2" ) isContainedIn("Drawer", "House"; ) then System.out.println( "Drawer is in the House" ); end
ksession.insert( "go2" ); ksession.fireAllRules();
go2 Drawer is in the House
isContainedIn(x==drawer, z==desk)
Location(x==drawer, y==desk)
rule "go3" when String( this == "go3" ) isContainedIn("Key", "Office"; ) then System.out.println( "Key is in the Office" ); end
ksession.insert( "go3" ); ksession.fireAllRules();
go3
ksession.insert( new Location("Key", "Drawer") ); ksession.fireAllRules();
Key is in the Office
rule "go4" when String( this == "go4" ) isContainedIn(thing, "Office"; ) then System.out.println( thing + "is in the Office" ); end
ksession.insert( "go4" ); ksession.fireAllRules();
go4 Chair is in the Office Desk is in the Office Key is in the Office Computer is in the Office Drawer is in the Office
rule "go5" when String( this == "go5" ) isContainedIn(thing, location; ) then System.out.println(thing + " is in " + location ); end
ksession.insert( "go5" ); ksession.fireAllRules();
go5 Chair is in Office Desk is in Office Drawer is in Desk Key is in Drawer Kitchen is in House Cheese is in Kitchen Knife is in Kitchen Computer is in Desk Office is in House Key is in Office Drawer is in House Computer is in House Key is in House Desk is in House Chair is in House Knife is in House Cheese is in House Computer is in Office Drawer is in Office Key is in Desk