Rules Engine - java(Drools) & ruby(ruleby)

Rule Engine– Java & RubyDrools & RulebyIng. Martín Cabreramartin.cabrera@moove-it.comMoove-ITContent Rules Engine ? What is this ? When to use ? RETE algorithm In Java - JBoss Drools features Syntax In ruby ?Motor de Reglas ¿what a #@!$ ?ApplicationRule engineRule def.knowledge baseRule defWhen to use? Infrastructure decoupled from the source  System to allow the final user to define their rules and change them dynamical y Developers are not the primary responsibility for changing rules Moderate or high complexity of business rules Performance ! Conclusion: down the rules of your system, so that they can be reused, decouple the code and al ow the user to know the rules ... to modify !Tipical Code01 if ((user.isMemberOf(AdministratorGroup) && user.isMemberOf(teleworkerGroup)) ||02 user.isSuperUser() {03 // more checks for specific cases04 if ((expenseRequest.code().equals("B203") ||05 (expenseRequest.code().equals("A903") && (totalExpenses < 200) &&06 (bossSignOff > totalExpenses)) && (deptBudget.notExceeded)) {07 // issue payments08 }09 else if {10 // check lots of other conditions11 }Change this rules ! ... %&”@ !12 }13 else {14 // even more business logic15 }16 }Rete Algorithm – the Solution ! Pattern matching algorithm for implementing production rule systems (wikipedia)http://en.wikipedia.org/wiki/Rete_algorithm replaces if ... Then with an optimized logic networkRete 2 RETE – characteristics: It reduces or eliminates certain types of redundancy through the use of node sharing. It stores partial matches when performing joins between different fact types.  It allows for efficient removal of memory elements when facts are retracted from working memory. Widely used to implement matching functionality within pattern-matching engines that exploit a match-resolve-act cycle to support forward and backward chaining and inferencing. Forward-chaining (facts -> goals) Backguard chaining (goals -> facts)Drools –  http://jboss.org/drools Introduction video - http://blog.athico.com/2010/03/fosdem-50-minute-introduction-into.html Introduction Rules engine framework for java It is used in other jboss projects like JBPM, SEAM, Jboss ESB and others The rules can be written in Java, Python, Groovy Ruby and your own rule language Jboss tools – plugin Eclipse to use this frameworkEclipse & DroolsSyntax or rules definitionrule “<name>” <attribute> <value> when <LHS> then <RHS>endDocument Outline

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