Rules Engine Overview Denver Java User's Group Sept 2007

Rules Engine Overview Scott Ryan September 2007

Agenda
Rule Systems Overview
Rule Development Options
Toolsets
Rule Management
Rule Modification
Sample Implementation

Overview

Major Components
Working Memory/Sessions
Rule Sets
Packages
Rules
Facts
Globals and Non Fact Objects

Working Memory
Stateful
Stateless
Can be dynamically updated
Data can push or pull between Working Memory

Rule Sets
Contain groupings of Rule Packages
Are associated with a Session

Packages
Contain sets of rules
Are serializable

Rules
Come in various formats
DRL/DSL
XML
Spreadsheet
BRMS
Spring annotated beans
Are serializable
Loaded using various techniques

XML Rule  <rule name="XYZCorp" salience="-1">  <parameter identifier="stockOffer"> <class>StockOffer</class> </parameter>  <java:condition>stockOffer.getStockName().equals("XYZ")</java:condition> <java:condition>stockOffer.getRecommendPurchase() == null</java:condition> <java:condition>stockOffer.getStockPrice() > 10</java:condition>  <java:consequence> stockOffer.setRecommendPurchase(StockOffer.NO); printStock(stockOffer); </java:consequence> </rule>

DRL Rule rule "Time Zone One" no-loop true when $w : WorkItem(address.state.value memberOf timeZoneOneStates); then $w.setPriority($w.getPriority()+ 128); end

Facts
Objects that Rules act upon
Follow Java Bean Rules
Can be dynamically updated
No limit to number, type or state of objects

Global and Non Fact Objects
Used to provide data or functions
Injected during packaging
Can be any Java object
Accessible via any Rule Format

Toolsets
Eclipse Based Development
Eclipse Based Debugging
Log Debugging

Rule Management
File and/or classpath loading
JNDI Loading
Database Loading
Pre-Compilation (Rules are serializable)
Pre-Packaging (Packages are serializable)
Caching Strategies

Rule Modification
Property or Database Driven
DSL based
BRMS based
XML Dynamic Modification

Sample Implementation
Simple Replacement of existing Business Rule Interface
Code

Problem Domain

Pros
Declarative Programming Model
Concentrate on the what not the how
Increased Performance
Speed and Scalability
Easily modified which increases coordination between business and IT
Separation of logic and data (Is this a good thing?)

Cons
New thought processes
Somewhat black box
Separation of code and logic breaks OO paradigm.

Spring Support Rule @Rule( name="Set Pump to Cooling", documentation="If a floors temperature becomes too hot, and the floor's pump is off, set the pump in the cooling state.", salience=10 ) public class PumpOffWhenFloorsWarmEnough {

Spring Support When @Condition public boolean isPumpOff(@Fact HeatPump pump) { return pump.getState() == OFF; }

Spring Support Then @Consequence public void consequence(HeatPump pump) { pump.setState(COOLING); }

Spring Configuration <bean id="pumpRuleSet" class="org.drools.spring.factory.RuleSetFactoryBean"> <property name="rules"> <set> <bean id="pump.OffWhenFloorsCoolEnough" ... /> <bean id="pump.OffWhenFloorsWarmEnough" .../> <bean id="pump.HeatingWhenFloorTooCold" .../> <bean id="pump.CoolingWhenFloorTooHot" .../> </set> </property> </bean>

Rules Engine Overview Denver Java User's Group Sept 2007

by Soaring Eagle L.L.C. on Feb 13, 2011

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Rules Engine Overview Denver Java User’s Group Sept 2007 — Presentation Transcript