Editing Jess (programming language)

{{Refimprove|date=March 2012}}
{{Infobox software
| name = Jess
| developer = [[Sandia National Laboratories]]
| released = {{Start date and age|1995}}
| latest release version = 7.1p2
| latest release date = {{Start date and age|2008|11|05}}
| programming language = [[Java (programming language)|Java]]
| platform = [[Java (software platform)|Java]]
| license = [[Proprietary software|Proprietary]], [[public domain]]
| website = {{URL|www.jessrules.com}}
}}
'''Jess''' is a [[rule engine]] for the [[Java (software platform)|Java]] [[computing platform]], written in the [[Java (programming language)|Java]] [[programming language]]. It was developed by [[Ernest Friedman-Hill]] of [[Sandia National Laboratories]].<ref name="ExpertSystems">{{cite book |last1=Hemmer |first1=Markus C. |date=2008 |url=https://books.google.com/books?id=KepsLbpWe-0C&dq=Jess%2C+Java&pg=PA47 |title=Expert Systems in Chemistry Research |publisher=CRC Press |pages=47–48 |isbn=9781420053241 |access-date=March 30, 2012}} {{ISBN|978-1-4200-5323-4}}</ref> It is a [[superset]] of the [[CLIPS]] language.<ref name="ExpertSystems"/> It was first written in late 1995.<ref name="ExpertSystems"/> The language provides [[rule-based programming]] for the automation of an [[expert system]], and is often termed as an ''expert system shell''.<ref name="ExpertSystems"/> In recent years, [[intelligent agent]] systems have also developed, which depend on a similar ability.

Rather than a [[Imperative programming|procedural paradigm]], where one program has a [[Loop (computing)|loop]] that is activated only one time, the [[Declarative programming|declarative paradigm]] used by Jess applies a set of rules to a set of facts continuously by a process named ''[[pattern matching]]''. Rules can modify the set of facts, or can execute any Java code. It uses the [[Rete algorithm]]<ref name="ExpertSystems"/> to execute rules.

==License==
The [[Software license|licensing]] for Jess is [[freeware]] for education and government use, and is [[proprietary software]], needing a license, for commercial use. In contrast, CLIPS, which is the basis and starting code for Jess, is [[free and open-source software]].

==Code examples==
Code examples:
<syntaxhighlight lang="lisp">
; is a comment

(bind ?x 100)

; x = 100

(deffunction max (?a ?b)
             (if (> ?a ?b) then ?a else ?b))

(deffacts myroom
          (furniture chair)
          (furniture table)
          (furniture bed)
          )

(deftemplate car
             (slot color)
             (slot mileage)
             (slot value)
             )

(assert (car (color red) (mileage 10000) (value 400)))
</syntaxhighlight>
Sample code:
<syntaxhighlight lang="lisp">
(clear)
(deftemplate blood-donor (slot name) (slot type))
(deffacts blood-bank ; put names & their types into [[working memory]]
          (blood-donor (name "Alice")(type "A"))
          (blood-donor (name "Agatha")(type "A"))
          (blood-donor (name "Bob")(type "B"))
          (blood-donor (name "Barbara")(type "B"))
          (blood-donor (name "Jess")(type "AB"))
          (blood-donor (name "Karen")(type "AB"))
          (blood-donor (name "Onan")(type "O"))
          (blood-donor (name "Osbert")(type "O"))
          )
(defrule can-give-to-same-type-but-not-self ; handles A > A, B > B, O > O, AB > AB, but not N1 > N1
         (blood-donor (name ?name)(type ?type))
         (blood-donor (name ?name2)(type ?type2 &:(eq ?type ?type2) &: (neq ?name ?name2) ))
         =>
         (printout t ?name " can give blood to " ?name2 crlf)
         )
(defrule O-gives-to-others-but-not-itself ; O to O cover in above rule
         (blood-donor (name ?name)(type ?type &:(eq ?type "O")))
         (blood-donor (name ?name2)(type ?type2 &: (neq ?type ?type2) &: (neq ?name ?name2) ))
         =>
         (printout t ?name " can give blood to " ?name2 crlf)
         )
(defrule A-or-B-gives-to-AB ; case O gives to AB and AB gives to AB already dealt with
         (blood-donor (name ?name)(type ?type &:(or (eq ?type "A") (eq ?type "B" ))))
         (blood-donor (name ?name2)(type ?type2 &: (eq ?type2 "AB") &: (neq ?name ?name2) ))
         =>
         (printout t ?name " can give blood to " ?name2 crlf)
         )
;(watch all)
(reset)
(run)
</syntaxhighlight>

==See also==
* [[Semantic reasoner]]
* [[Decision Model and Notation]] 

===Related systems===
* [[CLIPS]]: [[public-domain software]] tool to build expert systems
* [[ILOG]] rules: business rule management system
* JBoss [[Drools]]: business rule management system (BRMS)
* [[Prolog]]: general purpose logic programming language
* [[OpenL Tablets]]: business centric rules and BRMS
* DTRules: [[decision table]] based, open-source rule engine for Java

==References==
{{Reflist}}

===Further sources===
* {{cite book |last1=Friedman-Hill |first1=Ernest |date=2003 |url=https://books.google.com/books?id=-xxjRZhyF0IC&q=Jess+in+Action:+Rule+Based+Systems+in+Java |title=Jess in Action: Rule Based Systems in Java |publisher=Manning Publications |isbn=9781930110892 |access-date=March 30, 2012}} {{ISBN|1-930110-89-8}}

==External links==
* {{Official website|www.jessrules.com}}

[[Category:Expert systems]]
[[Category:Rule engines]]
[[Category:Knowledge representation languages]]
[[Category:Java APIs]]
[[Category:Sandia National Laboratories]]
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[[Category:Articles with example Lisp (programming language) code]]