Evaluate a Decision Table

This example evaluates decision tables, which are structured representations of rules and conditions that determine corresponding outcomes. By processing decision tables, users can automate decision-making processes based on complex sets of conditions and streamline the evaluation of multiple rules to arrive at the appropriate outcome.

Decision tables can be utilized to automate workflows by defining conditions that specify the next steps or actions to be taken. By evaluating decision tables within workflow systems, users can streamline and automate processes, improving efficiency and consistency in decision-making.

Java Code Listing

package com.northconcepts.datapipeline.foundations.examples.decisiontable;

import com.northconcepts.datapipeline.core.Record;
import com.northconcepts.datapipeline.foundations.decisiontable.DecisionTable;
import com.northconcepts.datapipeline.foundations.decisiontable.DecisionTableResult;
import com.northconcepts.datapipeline.foundations.decisiontable.DecisionTableRule;
import com.northconcepts.datapipeline.internal.expression.DefaultExpressionContext;

public class EvaluateADecisionTable {

    public static void main(String[] args) {
        DefaultExpressionContext input = new DefaultExpressionContext();
        input.setValue("Age", 49);
        input.setValue("House Owned", true);
        input.setValue("Income", 1000.0);
        
        DecisionTable table = new DecisionTable()
                .addRule(new DecisionTableRule()
                        .addCondition("Age", "? >= 40")
                        .addCondition("House Owned", "? == true")
                        .addOutcome("Eligible", "true")
                        )
                .addRule(new DecisionTableRule()
                        .addCondition("Age", "? >= 40")
                        .addCondition("House Owned", "? == false")
                        .addCondition("Income", "? >= 2000")
                        .addOutcome("Eligible", "true")
                        )
                .addRule(new DecisionTableRule()
                        .addCondition("Age", "? >= 40")
                        .addCondition("House Owned", "? == false")
                        .addCondition("Income", "? < 2000") 
                        .addOutcome("Eligible", "false")
                        )
                .addRule(new DecisionTableRule()
                        .addCondition("Age", "? < 40")
                        .addCondition("Income", "? >= 3000")
                        .addOutcome("Eligible", "true")
                        )
                .addRule(new DecisionTableRule()
                        .addCondition("Age", "? < 40")
                        .addCondition("Income", "? < 3000")
                        .addOutcome("Eligible", "false")
                        )
                ;
        
        DecisionTableResult result = table.evaluate(input);
        Record outcome = result.getOutcome();

        System.out.println("outcome = " + outcome);
    }

}

Code Walkthrough

1. A DefaultExpressionContext is defined as the input of the decision table where we set properties such as Age, House Owned and Income.
2. Then, a DecisionTable is initialized with rules defined in DecisionTableRule objects.
3. In order to add a condition to a rule, addCondition() method is called. As in the example, more than one condition can be applied to a single rule. 
4. addOutcome() method is invoked to attach an outcome with a rule.
5. The input is then evaluated and stored in a DecisionTableResult instance.
6. Finally, getOutcome() is invoked to display the results of the evaluation on the console.

Console Output

outcome = Record (MODIFIED) {
    0:[Eligible]:BOOLEAN=[true]:Boolean
}