Drools JBoss Rules 5.X Developer's Guide (repost)

Writing business rules has always been a challenging task. Business rules tend to change often leading to a maintenance nightmare. This book shows you various ways to code your business rules using Drools, the open source Business Rules Management System.
Drools JBoss Rules 5.X Developer’s Guide shows various features of the Drools platform by walking the reader through several real-world examples. Each chapter elaborates on different aspects of the Drools platform. The reader will also learn about the inner workings of Drools and its implementation of the Rete algorithm.

The book starts with explaining rule basics, then builds on this information by going through various areas like human readable rules, rules for validation, and stateful rules, using examples from the banking domain. A loan approval process example shows the use of the jBPM module. Parts of a banking fraud detection system are implemented with the Drools Fusion module which is the complex event processing part of Drools. Finally, more technical details are shown detailing the inner workings of Drools, the implementation of the ReteOO algorithm, indexing, node sharing, and partitioning.