drools-euos05

Recipe Finder – DRL File
• DRL Files are XML • Contain one or more Rules • Several Semantic Modules Available:
– Java – Groovy – Python
Recipe Finder - Loading the Rules
Integrating Drools
• In J2SE:
– Use native Drools APIs – Use JSR-94 Integration – Spring Pojo-Driven Rules
• In J2EE:
– Stateless Session Beans – JNDI – MBeans for Management
Recipe Finder - Domain
• Recipe Finder Domain Model
Recipe Finder - Procedural
• Traditional Procedural Approach
– Loop over all recipes – …check each recipe against available ingredients – …save the matching recipes
// Ingredients Ingredient rice = new Ingredient("rice"); Ingredient beans = new Ingredient("beans"); // Recipes Recipe riceAndBeans = new Recipe("Rice and Beans"); riceAndBeans.addIngredient(rice); riceAndBeans.addIngredient(beans);
Recipe Finder – Rule Firing
workingMemory.fireAllRules(); Output: Using drl: recipefinder.java.drl … You can make Rice and Beans You can make Ranchero Eggs
//Create a Working Memory WorkingMemory workingMemory = ruleBase.newWorkingMemory();
Recipe Finder – Asserting Facts
// assert facts - ingredients workingMemory.assertObject(rice); workingMemory.assertObject(chocolateCake); workingMemory.assertObject(eggs); … // assert facts - recipes workingMemory.assertObject(riceAndBeans); workingMemory.assertObject(chocolateCake); workingMemory.assertObject(pancakes); workingMemory.assertObject(rancheroEggs);
Loan Calculator - DSL Example
Loan Calculator - DSL Example
<rule name="XYZ-FicoScore"> <loans:condition> <loans:lender name="XYZ Mortage" /> <loans:application> <loans:fico> <loans:less-than>680</loans:less-than> </loans:fico> </loans:application> </loans:condition> <loans:actions> <loans:application name="messages"> <loans:add> Declined by XYZ Mortgage because a FICO score of at least 680 is required </loans:add> </loans:application> </loans:actions> </rule>
Drools
An Open Source Java Rules Engine
Brian Sam-Bodden Principal Partner Integrallis Software, LLC.
October 17 - 20, 2005
Contents
• A simple problem – Recipe Finder • Recipe Finder – Procedural Implementation • Introducing Drools • Recipe Finder – The Drools Way
Recipe Finder - Procedural
DEMO
Drools
• Forward Chaining Inference Engine • Based on Rete algorithm • Supports several languages for expressing Rules • Created by Bob McWhirter
Recipe Finder - Drools
<rule name=“RecipeMatch"> <parameter identifier="recipe"> <java:class>Recipe</java:class> </parameter> <java:condition> recipe.getIsComplete() </java:condition> <java:consequence> searchResults.addMatch(recipe); drools.retractObject(recipe); </java:consequence> </rultMatch Rule
•Matches an ingredient to a recipe
– RecipeMatch Rule
•Collects recipes with all ingredients matched
Recipe Finder - Drools
– Hosted at Codehaus – Open source, BSD Style License
• Simple API (few classes to master) • /
Drools – The Big Picture
Recipe Finder - Drools
Contents
• Rule Engine Applications • Domain Specific Languages • Integrating Drools • Drools Loan Calculator • Choosing to use a Rule Engine • Choosing a Rule Engine
<rule name="IngredientMatch"> <parameter identifier="recipe"> <java:class>Recipe</java:class> </parameter> <parameter identifier="ingredient"> <java:class>Ingredient</java:class> </parameter> <java:condition> recipe.containsIngredient(ingredient) </java:condition> <java:consequence> if (recipe.matchIngredient(ingredient)) { drools.modifyObject(recipe); } </java:consequence> </rule>
Recipe Finder - Procedural
• Matching Ingredients and Recipes
for ( Recipe recipe : recipes ) { for ( Ingredient ingredient : ingredients ) { recipe.matchIngredient(ingredient); } if (recipe.getIsComplete()) { searchResults.addMatch(recipe); } }
Recipe Finder Application
• Problem: Given a list of Ingredients and Recipes determine which recipes can be prepared
Recipe Finder - Domain
• The POJOs: Recipes and Ingredients
Recipe Finder - Drools
• Rules are declarative • Follow the pattern