March 2nd Cork JUG meet up

1. DroolsBasics&Common
Pitfalls
Mauricio Salatino / JBoss - Red Hat
JUG Cork March - 2016

2. Agenda
● What is Drools?
○ Drools History
○ Rule Engine
○ DRL language
○ Execution Cycle
● KIE - Knowledge is Everything
○ KIE Platform & KIE API
● Our First Drools Project
● Drools Common Usage
● Drools Common Pitfalls
● Roadmap (7.x version)

3. AboutMe
● Senior Software Engineer @ Red Hat/JBoss
● I joined the Drools & jBPM in 2012
● Passionate about Drools & jBPM
● Author of 3 books about jBPM
● New book about Drools
○ (1st April 2016)

4. WhatisDrools? -History
● 2003: Created by Mark Proctor and Bob McWhirter
● 2005: Acquired by JBoss
● 2007: Drools 3.x introduced the first version of the Rete
OO Algorithm
● 2009: Drools 4.x focused on performance and production
ready
● 2012: Drools 5.x focused on integration and unification
of Drools, jBPM and CEP (KIE was born)
● 2014: Drools 6.x focused on infrastructure, deployment
and tooling

5. WhatisDrools?
● It depends on what you need
○ Core: lightweight Rule Engine (a library)
○ KIE Server: standalone - as a service provider
● Rule Engine -> Inference Engine
○ Data Driven -> Forward Chaining Algorithms
○ Goal Driven -> Backward Chaining Algorithms
● Change of paradigm from Imperative (Java) to Declarative

6. WhatisDrools?-RuleStructure
rule “Large Orders require approval”
//<rule attributes>
when
Order(items.size >= 10 && total >= 100000)
then
// Trigger approval process
end

7. WhatisDrools?-RuleENgineOverview

8. WhatisDrools? -RuleExecutionCycle

9. KIEPlatform
● Drools
● Drools CEP (Fusion)
● jBPM
● OptaPlanner
● KIE Server (Drools, jBPM & CEP unified server)
● Uberfire (uberfireframework.com)
○ KIE Workbench (Drools, jBPM, Optaplanner Authoring, Runtime &
monitoring)
○ KIE Drools Workbench (Drools Authoring)

10. KIEAPIs
● KieContainer
● KieBase
● KieSession
○ insert(Object)
○ retract(FactHandle)
○ update(FactHandle, Object)
○ fireAllRules() / fireAllRules(int)
● KieScanner
● kmodule.xml
Drools Specific

11. OurFirstDroolsProject
● Simple JAR Java Maven Project
● Add Maven Dependencies
○ drools-compiler
■ drools-core (transitive)
■ kie-api (transitive)
● CDI Enabled
○ cdi-api
○ weld-se-core
○ beans.xml
● KIE specific
○ kmodule.xml
■ conventions over configurations

12. RulesPower
● Any Java Model (non-intrusive)
● Filter Data (Simple Filters)
● Correlate Data (Multiple filters between patterns)
● Accumulations / Aggregations (accumulate functions)
● Inference Chain
○ Detailed Log
○ Query Data
○ Truth Maintenance System(TMS)

13. CommonPitfalls
● Start simple, don’t over complicate things
● Compare with if/else statements
● Too much logic on the RHS
● Infinite Loop
● Complex (Nested) Models - Facts VS Non-Facts
● Cross Product - DB/SQL analogy
● From/Eval executed multiple time in RHS
○ External Service Calls (Sync calls)
● Persistence

14. Roadmap(7.xseries)
● Cloud Deployments
● Tooling for the Cloud
● Self-service applications
● Different Vertical’s Packages
● API refactoring towards
○ Flexibility
○ Services
○ Composition
● Drools language improvements
● Phreak tuning and fragmentation for distribution

15. Community
● www.drools.org / www.jbpm.org
● Drools & jBPM Mailing lists
● irc.freenode.net
○ #drools
○ #jbpm
● Blogs:
○ blog.athico.com
○ salaboy.com

16. Questions?

17. RETENetwork

18. Phreak