Drools - Business Rules Management System (Java™, Open Source)

Drools is a Business Rules Management System (BRMS) solution. It provides a core Business Rules Engine (BRE), a web authoring and rules management application (Drools Workbench), full runtime support for Decision Model and Notation (DMN) models at Conformance level 3 and an Eclipse IDE plugin for core development. Drools is open source software, released under the Apache License 2.0. It is written

[stakaya]

javaで作られているルールエンジン。スプレットシートでルールを作成することができる。ビジネスロジックが複雑だったり冗長だったりする時に使うと良いらしい。

[sasabe]

ルールエンジン

[kumicit]

Hmm... Somewhat improved since I tried it.

[IanLewis]

Drools 5 introduces the Business Logic integration Platform which provides a unified and integrated platform for Rules, Workflow and Event Processing. It's been designed from the ground up so that each aspect is a first class citizen, with no compromises.