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1.
Drools5 Community Training
Rete Algorithm Introduction
Sponsored by Plugtree

2. Module 4: Drools Expert
RETE Algorithm
Drools5 Community Training
version: 1.0-SNAPSHOT
Release Date: 03/16/2011
Under The Creative Common License

3. Module 1: Drools Expert
RETE Algorithm
Drools5 Community Training Course
by Mauricio "Salaboy" Salatino is
licensed under a Creative Commons
Attribution 3.0 Unported License.
Based on a work at salaboy.wordpress.
com.
Permissions beyond the scope of this
license may be available at http:
//salaboy.wordpress.com/.

4. Agenda
● RETE Algorithm:
○ Introduction
○ Characteristics
○ Rules activation & firing
○ RETE network structure and nodes

5. Agenda
● Theoretical Background
● Drools Business Logic Integration Platform Introduction
○ Drools Expert
○ jBPM5 / Drools Flow
○ Drools Fusion
○ Drools Guvnor

6. RETE Introduction
The RETE algorithm is an efficient pattern matching
algorithm for implementing production rule systems

7. RETE characteristics
● Model the rules as a network with different node types
● The node type will work as a filter
● We will insert our facts inside this network
● The facts will flow through the network only passing the
nodes that they match
● This network will sacrifice memory for performance

8. RETE net structure

9. Object Type Nodes
● Filter facts based on their types

10. Alpha network
● Contains the alpha nodes
● Filters facts based on single attributes

11. Beta network
● Contains the beta nodes
also known as two
input nodes
● Represents the join
relationships between
different patterns
● Song(genre == "Jazz")
AND
Artist(name == "John")

12. Beta network
● Song(genre == "Jazz",
$artist: artist)
AND
Artist(this == $artist,
name == "John")

13. Facts match a Rule => Activation

14.
Questions?

15. Enjoy! Questions and Feedback are
always appreciated!

16.
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