Introduction to CLIPS (Lecture Note #17)

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Introduction to CLIPSIntroduction to CLIPS(Lecture Note #17)(Lecture Note #17)

인공지능

이복주단국대학교 컴퓨터공학과

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OutlineOutline

Expert Systems: Principles and Programming, Joseph Giarratano & Gary Riley, PWS Publishing Company, 1998– Chapter 7 Introduction to CLIPS– Chapter 8 Pattern Matching

Introduction to Expert Systems, Peter Jackson– Appendix CLIPS Programming

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IntroductionIntroduction

Three types of programming paradigms in CLIPS– Rule-based– Object-oriented– Procedural

Will focus on rule-based– Three components: fact list, knowledge base (rules),

inference engine

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CLIPSCLIPS

Support rule-based, object-oriented, and procedural programming

Programming language style is similar to OPS5, but more powerful

Support only forward chaining rules– Not backward chaining

COOL: CLIPS Object-Oriented Language– Extension of Common Lisp Object System (CLOS)– Syntactically similar to LISP

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CLIPSCLIPS

CLIPS: C Language Integrated Production System– Designed at NASA Johnson Space Center, mid-80s– High portability, low cost, easy integration with

external system– Original CLIPS supported only rule-based (note:

Production System)– CLIPS version 5.0 added procedural and OO– Due to its portability, installed various computers

from PCs to CRAY– Runs on UNIX, DOS, Windows, and Macintosh– Maintained as public domain software

• E.g., http://www.cosmic.uga.edu

– Downloadable by anonymous ftp• e.g.,

http://www-cgi.cs.cmu.edu/afs/cs/project/ai-repository/ai/areas/expert/systems/clips

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NotationNotation

(example) (example [1]) ; optional

– (example)– (example 1)

(example <integer>)– <> means replacement– (example 1)– (example 5)– (example –20)

<integer>*– * means zero or more– 1– 1 2– 1 2 3

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NotationNotation

<integer>+ – + means one or more– <integer>+ is same as <integer> <integer>*

All | none | some– | indicates a choice

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FieldField

Tokens– Group of characters– Some tokens consist of one character: e.g., ‘(‘, ‘)’

Field: special tokens– Seven types of field– Float, integer, symbol, string, external address,

instance name, instance address Numerical fields: Float, integer

– Float: 1.5, 1.0, 0.7, 9e+1, 3.5e10– Integer: 1, +3, -1, 65

Symbol– Starts with printable ASCII character, followed by

zero or more characters

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FieldField

Delimiters– Any non-printable ASCII characters (spaces, tabs, CRs, LFs)– “ (double quote)– ( (opening parenthesis)– ) (closing parenthesis)– ; (semi colon)– & (ampersand)– | (vertical bar)– ~ (tilde)– < (less than)

?, $: variable– Cannot be placed at the beginning of a symbol

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FieldField

Examples of valid symbols– Space-Station– February– fire– Activate_sprinkler_system– notify-fire-department– !?#$^*– 345B– 346-95-6156

Case-sensitive– Case-sensitive– Case-Sensitive– CASE-SENSITIVE are different symbols

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FieldField

String– Begin and end with double quotation– Examples of valid strings

• “Activate the sprinkler system.”• “!?#$^”• “John Q. Public”

– Spaces in a string are preserved• “spaces”• “spaces “• “ spaces”• “ spaces “ are different strings

– “”three-tokens””• “”• three-tokens• “”

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FieldField

“\”single-token\””– “”single-token””: one string field

“\\single-token\\”– “\single-token\”: one string field

External addresses, instance addresses, instance names– Of little interest in rule-based

Multi-field value– Zero or more fields– When calling a function– (): zero length multi-field– (this that): multi-field containing the symbols this

and that

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Entering and Exiting CLIPSEntering and Exiting CLIPS

CLIPS> – CLIPS prompt– Top level: Commands can be entered directly

(exit): exiting command– Vs. exit: a symbol

Parentheses should be matched and balanced ex<enter-key>it

– Two tokens: ex and it A command sequence

– CLIPS> exit ; exit is a symbol– exit– CLIPS> (+ 3 4) ; a function– 7– CLIPS> (exit) ; exit command

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FactsFacts

Facts consists of– Relation name: a symbolic field– Zero or more slots: also symbolic fields– Associated values

Example– (person (name “John Q. Public”)– (age 23)– (eye-color blue)– (hair-color black))

Order of slots are irrelevant– (person (hair-color black)– (name “John Q. Public”)– (age 23)– (eye-color blue)– is the same as above

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Deftemplate ConstructDeftemplate Construct

Deftemplate construct– Groups of facts share the same relation name– The common information is described– Analogous to a record structure in Pascal and C

General format– (deftemplate <relation-name> [<optional-comment>] <slot-definitio

n>*) <slot-definition>

– (slot <slot-name>) | (multislot <slot-name>) Person fact

– (deftemplate person “An example deftemplate”– (slot name)– (slot age)– (slot eye-color)– (slot hair-color))

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Multi-field SlotsMulti-field Slots

Place one or more fields into a given slot Person deftemplate

– (deftemplate person “An example deftemplate”– (multislot name)– (slot age)– (slot eye-color)– (slot hair-color))

Person fact– (person (name John Q. Public)– (age 23)– (eye-color blue)– (hair-color black))

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Ordered FactsOrdered Facts

Ordered facts– Does not have a corresponding deftemplate– Slot name is not required

Example– (number-list 7 9 3 4 20)

Equivalent to – (deftemplate number-list (multislot values)– (number-list (values 7 9 3 4 20))

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Adding and Removing FactsAdding and Removing Facts

Facts are added and removed from the fact list Assert command: add a fact

– (assert <fact>+) Example

– CLIPS> – (deftemplate person– (slot name)– (slot age)– (slot eye-color)– (slot hair-color))– CLIPS>– (assert (person (name “John Q. Public”)– (age 23)– (eye-color blue)– (hair-color black)))– <Fact-0> ; assert returns a value– CLIPS>

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Facts command– (facts)– Displays the facts in the fact list

Example– CLIPS> (facts)– f-0 (person (name “John Q. Public”)– (age 23)– (eye-color blue)– (hair-color black))– For a total of 1 fact.– CLIPS>

f-0: fact identifier– 0: fact index

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Duplicate facts are not allowed Adding another facts

– CLIPS>– (assert (person (name “Jane Q. Public”)– (age 36)– (eye-color green)– (hair-color red)))– <Fact-1>– CLIPS> (facts)– f-0 (person (name “John Q. Public”)– (age 23)– (eye-color blue)– (hair-color black))– f-1 (person (name “Jane Q. Public”)– (age 34)– (eye-color green)– (hair-color red))– For a total of 2 facts.– CLIPS>

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Adding more than one facts– (assert (person (name “Jane Q. Public”)– (age 36)– (eye-color green)– (hair-color red))– (person (name “Jane Q. Public”)– (age 34)– (eye-color green)– (hair-color red)))

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Viewing a portion of fact list– (facts [<start> [<end> [<maximum>]]])– No more than <maximum> facts are displayed

Removing a fact– The deleted fact identifier will be missing– Called retraction– (retract <fact-index>+)

• (retract 0) ; John Q. Public removed• (retract 1) ; Jane Q. Public removed

Removing non-existent fact– CLIPS> (retract 1)– CLIPS> (retract 1)– [PRNTUTIL1] Unable to find fact f-1.– CLIPS>

Retract multiple facts– (retract 0 1)

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Modifying and Duplicating FactsModifying and Duplicating Facts

Modify command– Slot values of deftemplate facts can be modified– (modify <fact-index> <slot-modifier>+)

<slot-modifier>– (<slot-name> <slot-value>)

Example: John Q. Public’s age is increased– CLIPS> (modify 0 (age 24)) – <Fact-2> – CLIPS> (facts)– f-2 (person (name “John Q. Public”) ; new index– (age 24)– (eye-color blue)– (hair-color black))– For a total of 1 fact.– CLIPS>

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Modifying and Duplicating FactsModifying and Duplicating Facts

Duplicate command– Same as modify except– does not retract the original fact

Example– CLIPS> (duplicate 2 (name “Jack S. Public”))– <Fact-3>– CLIPS> (facts)– f-2 (person (name “John Q. Public”)– (age 24)– (eye-color blue)– (hair-color black))– f-3 (person (name “Jack S. Public”)– (age 24)– (eye-color blue)– (hair-color black))– For a total of 2 facts.– CLIPS>

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The Watch CommandThe Watch Command

Watch command– For debugging– (watch <watch-item>)

<Watch-item>– One of the symbols:

facts, rules, activations, statistics, compilations, focus, all

Example– CLIPS> (facts 3 3)– f-3 (person (name “Jack

S. Public”)– (age 24)– (eye-color blue)– (hair-color

black))– For a total of 1 fact.

– CLIPS> (watch facts)– CLIPS> (modify 3 (age 25))– <== f-3 (person (name “Jack S. Pu

blic”)– (age 24)– (eye-color blue)– (hair-color black))– ==> f-4 (person (name “Jack S. Pu

blic”)– (age 25)– (eye-color blue)– (hair-color black))– <Fact-4>– CLIPS>

Unwatch– (unwatch <watch-item)

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Deffacts ConstructDeffacts Construct

Assert a set of facts– (deffacts <deffacts name> [<optional comments>] <facts>*)

example– (deffacts people “Some people we know”– (person (name “John Q. Public”) (age 24)– (eye-color blue) (hair-color black))– (person (name “Jack S. Public”) (age 24)– (eye-color blue) (hair-color black))– (person (name “Jane Q. Public”) (age 36)– (eye-color green) (hair-color red)))

Assert the deffatcs statement– (reset)

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Deffacts ConstructDeffacts Construct

Example– CLIPS> (unwatch facts)– CLIPS> (reset)– CLIPS> (facts)– f-0 (initial-fact) ; new fact by reset command– f-1 (person (name “John Q. Public”) (age 24)– (eye-color blue) (hair-color black))– f-2 (person (name “Jack S. Public”) (age 24)– (eye-color blue) (hair-color black))– f-3 (person (name “Jane Q. Public”) (age 36)– (eye-color green) (hair-color red))– For a total of 4 facts.– CLIPS>

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The Components of a RuleThe Components of a Rule

A rule example– In an industrial plant monitoring expert system– IF the emergency is a fire – THEN the response is to activate the sprinkler system

Define template for the emergency and response– (deftemplate emergency (slot type))

• type could be fire, flood, power outage

– (deftemplate response (slot action)) Define rule

– (defrule fire-emergency “An example rule”– (emergency (type fire))– =>– (assert (response (action activate-sprinkler-system))))

General format– (defrule <rule name> [<comment>]– <pattern>* ; LHS of the rule– =>– <actions>*) ; RHS of the rule

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The Agenda and ExecutionThe Agenda and Execution

Agenda– The collection of activated rules

Salience– The priority of a rule in integer

Run command– (run <limit>)

• <limit>: maximum number of rules to be fired

Displaying the agenda– (agenda)

Example– CLIPS> (reset)– CLIPS> (assert (emergency (type fire)))– <Fact-1>– CLIPS> (agenda)– 0 fire-emergency: f-1 ; salience, rule, fact– For a total of 1 activation.– CLIPS>

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Rules and RefractionRules and Refraction

Run command– CLIPS> (run)– CLIPS> (facts)– f-0 (initial-fact)– f-1 (emergency (type fire))– f-2 (response (action activate-sprinkler-system))– For a total of 3 facts.– CLIPS>

refraction– Rules are not fired more than once for a specific set of facts

(clear)– removes all constructs and all facts– Vs. (reset) asserts the deffacts statement

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The Printout CommandThe Printout Command

Printout command– (printout <logical-name> <print-items>*)

Example– (defrule fire-emergency– (emergency (type fire))– =>– (printout t “Activate the sprinkler system” crlf))– ; t: terminal, destination name

Using multiple rules– (defrule flood-emergency– (emergency (type flood))– =>– (printout t “Shut down electrical equipment” crlf))

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Using Multiple PatternsUsing Multiple Patterns Rules with multiple patterns

– (deftemplate extinguisher-system– (slot type)– (slot status))– (defrule class-A-fire-emergency– (emergency (type class-A-fire))– (extinguisher-system (type water-sprinkler)– (status off))– =>– (printout t “Activate water sprinkler” crlf))– (defrule class-B-fire-emergency– (emergency (type class-B-fire))– (extinguisher-system (type carbon-dioxide)– (status off))– =>– (printout t “Use carbon dioxide extinguisher” crlf))

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Loading and Saving ConstructLoading and Saving Construct

Loading constructs from a file– (load <file-name>)– E.g., (load “fire.clp”)

Watching compilation– CLIPS> (load “fire.clp”)– Defining deftemplate: emergency– Defining deftemplate: response– Defining defrule: fire-emergency– TRUE– CLIPS>

No watch– CLIPS> (clear)– CLIPS> (unwatch compilations)– CLIPS> (load “fire.clp”)– %%* ; % for defconstruct * for rule– TRUE– CLIPS>

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Saving Construct to a FileSaving Construct to a File

(save <file-name>)– E.g., (save “fire.clp”)– Saves all the constructs

Saving partial constructs– Use an text editor

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VariablesVariables

Variables– Question mark followed by symbol– e.g., ?speed, ?sensor, ?value, ?noun, ?color

Bind– Assignment of a value to a variable

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VariablesVariables

Example– CLIPS> (clear)– CLIPS>– (deftemplate person– (slot name) – (slot eyes)– (slot hair))– CLIPS>– (defrule find-blue-eyes)– (person (name ?name) (e

yes blue))– =>– (printout t ?name “ has bl

ue eyes.” crlf))

– CLIPS> – (deffacts people– (person (name Jane)– (eyes blue) (hair red))– (person (name Joe)– (eyes green) (hair brown))– (person (name Jack)– (eyes blue) (hair black))– (person (name Jeff)– (eyes green) (hair brown)))– CLIPS> (reset) – ; Assert the deffatcs– CLIPS> (run)– Jack has blue eyes.– Jane has blue eyes.– CLIPS>

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Blocks WorldBlocks World

Blocks world initial configuration

Facts about which blocks are on top of others– (deftemplate on-top-of– (slot upper)– (slot lower))– (on-top-of (upper A) (lower B))– (on-top-of (upper B) (lower C))– (on-top-of (upper D) (lower E))– (on-top-of (upper E) (lower F))– (on-top-of (upper nothing) (lower A))– (on-top-of (upper C) (lower floor))– (on-top-of (upper nothing) (lower D))– (on-top-of (upper F) (lower floor))

C

B

A

F

E

DGoal: C on top of E

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Floor and nothing are not blocks– (block A)– (block B)– (block C)– (block D)– (block E)– (block F)

Describe the goal– (deftemplate goal (slot move) (slot on-top-of))– (goal (move C) (on-top-of E))– on-top-of was also a template name in the prev page

Initial state– (deffatcs initial-state– (block A)– …– (on-top-of …– …– (goal (move C) (on-top-of E)))

C

B

A

F

E

D

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Move-directly rule– (defrule move-directly– ?goal <- (goal (move ?block1) – (on-top-of ?block2))– (block ?block1)– (block ?block2)– (on-top-of (upper nothing) (lower ?block1))– ?stack-1 <- (on-top-of (upper ?blocks1) (lower ?block3))– ?stack-2 <- (on-top-of (upper nothing) (lower ?block2))– =>– (retract ?goal ?stack-1 ?stack-2)– (assert (on-top-of (upper ?block1) (lower ?block2))– (on-top-of (upper nothing) (lower ?block3)))– (printout t ?block1 “moved on top of “ ?block2 “.” crlf))

block3

block1

block2

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Move-to-floor rule– (defrule move-to-floor– ?goal <- (goal (move ?block1) – (on-top-of floor))– (block ?block1)– (on-top-of (upper nothing) (lower ?block1))– ?stack <- (on-top-of (upper ?block1) (lower ?block2))– =>– (retract ?goal ?stack)– (assert (on-top-of (upper ?block1) (lower floor))– (on-top-of (upper nothing) (lower ?block2)))– (printout t ?block1 “moved on top of floor.“ crlf))

block2

block1

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Clear-upper-block rule– (defrule clear-upper-block– (goal (move ?block1)) ; move is a slot of goal– (block ?block1)– (on-top-of (upper ?block2) (lower ?block1))– (block ?block2)– =>– (assert (goal (move ?block2) (on-top-of floor))))

Clear-lower-block rule (actually clear the top of block)– (defrule clear-lower-block– (goal (on-top-of ?block1)) ; on-top-of is a slot of goal– (block ?block1)– (on-top-of (upper ?block2) (lower ?block1))– (block ?block2)– =>– (assert (goal (move ?block2) (on-top-of floor))))

block1

block2

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Run– CLIPS> (reset)– CLIPS> (run)– A moved on top of floor.– B moved on top of floor.– D moved on top of floor.– C moved on top of E.– CLIPS>

C

B

A

F

E

D

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Functions and ExpressionsFunctions and Expressions

Elementary math functions– CLIPS> (+ 2 2)– 4– CLIPS> (/ 2 3)– 0.666667– CLIPS> (+ 2 3.0)– 5.0– CLIPS> (+ 2 3 4)– 9– CLIPS> (- 2 3 4)– -5– CLIPS> (+ 2 (* 3 4))– 14

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Functions and ExpressionsFunctions and Expressions

Embed the expression within other expressions– CLIPS> (clear)– CLIPS> (assert (answer (+ 2 3)))– <Fact-0>– CLIPS (facts)– f-0 (answer 4)– For a total of 1 fact.– CLIPS>

Function names are also symbols– CLIPS> (clear)– CLIPS> (assert (expression 2 + 3 * 4))– <Fact-0>– CLIPS> (facts)– f-0 (expression 2 + 3 * 4)– For a total of 1 fact.– CLIPS>

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I/O FunctionsI/O Functions

The read function– CLIPS> (clear)– CLIPS>– (defrule get-first-name– => ; no pattern– (printout t “What is your first name? “)– (bind ?response (read))– (assert (user’s-name ?response)))– CLIPS> (reset)– CLIPS> (run)– What is your first name? Gary– CLIPS> (facts)– F-0 (initial-fact)– F-1 (user’s-name Gary)– For a total of 2 facts.– CLIPS>

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Open function– (open <file-name> <file-ID> [,file-access.])– E.g., (open “input.dat” data “r”)

• Can use “w”, “r+”, “a” also

Close function– (close [<file-ID>])– E.g., (close data)

Writing to a file– CLIPS> (open “example.dat” example “w”)– TRUE– CLIPS> (printout example “green” crlf)– CLIPS> (printout example 7 crlf)– CLIPS> (close example)– TRUE– CLIPS>

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Reading from a file– CLIPS> (open “example.dat” example “r”)– TRUE– CLIPS> (read example)– green– CLIPS> (read example)– 7– CLIPS> (read example)– EOF– CLIPS> (close example)– TRUE– CLIPS>

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The readline function– CLIPS> (clear)– CLIPS>– Defrule get-name– =>– (printout t “What is your name? “)– (bind ?response (readline))– (assert (user’s-name ?response)))– CLIPS> (reset)– CLIPS> (run)– What is your name? Gary Riley– CLIPS> (facts)– F-0 (initial-fact)– F-1 (user’s-name “Gary Riley”)– For a total of 2 facts.– CLIPS>

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The readline function with multi-field– CLIPS> (clear)– CLIPS>– Defrule get-name– =>– (printout t “What is your name? “)– (bind ?response (explode$ (readline)))– (assert (user’s-name ?response)))– CLIPS> (reset)– CLIPS> (run)– What is your name? Gary Riley– CLIPS> (facts)– F-0 (initial-fact)– F-1 (user’s-name Gary Riley)– For a total of 2 facts.– CLIPS>

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SummarySummary

Expert Systems: Principles and Programming, Joseph Giarratano & Gary Riley, PWS Publishing Company, 1998– Chapter 7 Introduction to CLIPS– Chapter 8 Pattern Matching

Introduction to Expert Systems, Peter Jackson– Appendix CLIPS Programming

Documents

Introduction to CLIPS (Lecture Note #17)