 | This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Jess" programming language – news · newspapers · books · scholar · JSTOR (March 2012) (Learn how and when to remove this message) |
| Developer(s) | Sandia National Laboratories |
|---|---|
| Initial release | 1995; 30 years ago (1995) |
| Stable release | 7.1p2 / November 5, 2008; 16 years ago (2008-11-05) |
| Written in | Java |
| Platform | Java |
| License | Proprietary, public domain |
| Website | www |
Jess is a rule engine for the Java computing platform, written in the Java programming language. It was developed by Ernest Friedman-Hill of Sandia National Laboratories. It is a superset of the CLIPS language. It was first written in late 1995. The language provides rule-based programming for the automation of an expert system, and is often termed as an expert system shell. In recent years, intelligent agent systems have also developed, which depend on a similar ability.
Rather than a procedural paradigm, where one program has a loop that is activated only one time, the 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 to execute rules.
License
The 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:
; 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)))
Sample code:
(clear)
(deftemplate blood-donor (slot name) (slot type))
(deffacts blood-bank ; put names & their types into ]
(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)
See also
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
- ^ Hemmer, Markus C. (2008). Expert Systems in Chemistry Research. CRC Press. pp. 47–48. ISBN 9781420053241. Retrieved March 30, 2012. ISBN 978-1-4200-5323-4
Further sources
- Friedman-Hill, Ernest (2003). Jess in Action: Rule Based Systems in Java. Manning Publications. ISBN 9781930110892. Retrieved March 30, 2012. ISBN 1-930110-89-8