Introduction to Drools

eBusiness Technologies (ebTech) Introduction to Drools Adrian Giurca, eBusiness Technologies, Craiova, March 2009 Dr. Adrian Giurca Brandenburg University of Technology Cottbus, Germany

Repetition ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Developing Rule-based applications ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Drools Vocabulary is basically POJO package org.btu.it.userv.vocabulary; class YoungDriver extends Driver { // properties //default constructor public YoungDriver(){ } //setters and getters for the properties } Adrian Giurca, eBusiness Technologies, Craiova, March 2009 ,[object Object]

Rules are grouped in rulesets ,[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Sample ruleset (package) package org.btu.it.userv.driverPremium #list any import classes here. import org.btu.it.userv.vocabulary.YoungDriver; import java.io.IOException; // ... #declare any global variables here global java.io.BufferedWriter out; global org.btu.it.userv.utils.Output writer; // Rules #write any global function here function void writeLog(String text, BufferedWriter out)throws IOException{ // function code comes here } # or imports such as import function org.btu.it.userv.utils.Logger.writeLog Adrian Giurca, eBusiness Technologies, Craiova, March 2009 Ruleset name Vocabulary Global variables Global functions

Drools Rule structure ,[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Rules condition part (LHS) ,[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Actions (the RHS) ,[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Standard Actions in RHS ,[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Slide No. 11 ,[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

The basic pattern ,[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 For example: $driver:Driver(age < 25) The $driver variable is bound sequentially to all Driver objects from the working memory for which the age value is less than 25 , something like:  X driver( X ) && age( X ) < 25

Constraints (1) ,[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 For example: $driver:Driver(age < 25) age < 25 is a (field) constraint

Constraints (2) ,[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 ,[object Object],[object Object],[object Object]

Field constraints (1) ,[object Object],[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Field constraints (2) ,[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 ,[object Object],[object Object],[object Object]

The eval pattern and inlineEvalConstraint ,[object Object],[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 For example: eval(isApprovedByManager($client, $vip)) supposing isApprovedByManager() be a Boolean function.

Advanced patterns - from ,[object Object],[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 For example: $item : OrderItem( value > 100 ) from $order.items $item is bounded sequentially to all OrderItem objects with value greater than 100 from the list $order.items

More complex from : using collect ,[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009 $drivers : ArrayList() from collect( Driver( gender == 'F', noOfAccidents > 0 ) from $town.getDrivers() )

More complex from: using accumulate ,[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Accumulate example $total : Number( doubleValue > 100 ) from accumulate( OrderItem( order == $order, $value : value ), init( double total = 0; ), action( total += $value; ), reverse( total -= $value; ), result( total ) ) Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Do you like rule-based applications? ,[object Object],[object Object],Adrian Giurca, eBusiness Technologies, Craiova, March 2009

Introduction to Drools

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Introduction to Drools