Clara is a forward-chaining rules engine written in Clojure(Script) with Java interoperability. It aims to simplify code with a developer-centric approach to expert systems. See clara-rules.org for more.

NOTE: this fork only supports the JVM/Clojure, and not ClojureScript. See CHANGES.md for a full inventory of changes.

This project is an open source derivative work based on the Clara Rules project originally developed by Cerner and Oracle.

All original code remains Copyright (c) 2018-2023 Oracle and/or its affiliates. All subsequent improvements and maintenance are Copyright (c) 2023 Gateless, Inc.

This project retains the same API and namespaces as the original Clara Rules project, so it should be a drop-in replacement for any existing code using Clara Rules. The only exception is that ClojureScript support has been removed, so any code using Clara Rules in ClojureScript will need to be updated to use this fork. Some interfaces for more advanced features such as custom rules loaders and async rule firing have also been updated and may require some minor adjustments to existing code using those features. See CHANGES.md for a full inventory of changes.

Here's a simple example. For the latest API docs and examples visit here.

(ns clara.support-example
  (:require [clara.rules :refer :all]
            [futurama.core :refer [!<!!]))

(defrecord SupportRequest [client level])

(defrecord ClientRepresentative [name client])

(defrule is-important
  "Find important support requests."
  [SupportRequest (= :high level)]
  =>
  (println "High support requested!"))

(defrule notify-client-rep
  "Find the client representative and send a notification of a support request."
  [SupportRequest (= ?client client)]
  [ClientRepresentative (= ?client client) (= ?name name)] ; Join via the ?client binding.
  =>
  (println "Notify" ?name "that"  ?client "has a new support request!"))

;; We can just use Clojure's threading macro to wire things up below.

;; Run the rules!
(-> (mk-session)
    (insert (->ClientRepresentative "Alice" "Acme")
            (->SupportRequest "Acme" :high))
    (fire-rules))

;; Run the rules asynchronously!
(!<!! (-> (mk-session)
          (insert (->ClientRepresentative "Alice" "Acme")
                  (->SupportRequest "Acme" :high))
          (fire-rules-async {:parallel-batch-size 50})))

;;;; Prints this:

;; High support requested!
;; Notify Alice that Acme has a new support request!

Clara is built, tested, and deployed using Clojure Tools Deps.

GNU Make is used to simplify invocation of some commands.

Clara releases for this project are on Clojars. Simply add the following to your project:

• Questions about Clara rules can be posted to the Clara Rules Google Group or the Slack channel.
• For any other questions or issues about this Clara rules fork specifically feel free to browse or open a Github Issue.

See CONTRIBUTING.md

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Copyright (c) 2023 Gateless, Inc.

Copyright (c) 2018, 2023 Oracle and/or its affiliates.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.