© C. Kemke CLIPS 1 1 COMP 4200: Expert Systems Dr. Christel Kemke Department of Computer Science University of Manitoba

© C. Kemke CLIPS 1 2 CLIPS Introduction 2 Review and Introduction 2  CLIPS Programming System  Basic CLIPS Constructs and Syntax  Fields and Templates  Complex Condition Patterns  Input and Output  Salience

© C. Kemke CLIPS 1 3 CLIPS – Programming Systems CLIPS Interpreter  enter commands, direct modification of fact base... CLIPS File-Menu  load, save and edit CLIPS program files CLIPS Edit-Menu  Balance (ctrl B), Comment CLIPS Execution-Menu  set execution parameters (e.g. reset, run, clear, watch, constraint checking, halt) CLIPS Browse-Menu  manage and info about constructs CLIPS Window-Menu  current status info, e.g. Facts, Activations, …

© C. Kemke CLIPS 1 4 Working with Facts Changing fact base  Adding facts(assert )  Deleting facts(retract )  Modifying facts(modify (deftemplate facts) ( ))  Duplicating facts(duplicate (deftemplate facts) ( )) Monitoring program execution  Print all facts(facts)  Displays changes(watch facts), also for rules...  Dribblerecord trace into file

© C. Kemke CLIPS 1 5 CLIPS – Basic Constructs Basic Language Elements:  Fields(basic Data Types; slot fillers)  Facts(used in condition patterns)  Rules(condition-action rules)  Templates(like records; define facts)  Classes (like objects; define facts)  Messagehandlers (like methods defined for classes; used in condition patterns and actions)

© C. Kemke CLIPS 1 6 Fields - Examples Fields (data types)  float4.00, 2.0e+2, 2e-2  integer4, 2, 22  symbolAlpha24*,  string“Johnny B. Good”  instance name[titanic], [PPK] Variables ?var, ?x, ?dayvariables for single field value $?namesvariable for multi-field value

© C. Kemke CLIPS 1 7 Template and Fact with Single Field Single value in a slot: (person (name "Johnny B. Good" ) (age 42)) Defined based on: (deftemplate person (slot name) (slot age)) A single field slot stores one single field value, e.g. the string "Johnny B. Good" or the integer / number 42 in the example above.

© C. Kemke CLIPS 1 8 Multislots and Multifields More than one value in a slot: (person (name Johnny B. Good) (age 42)) Defined based on: (deftemplate person (multislot name) (slot age)) A multi-slot allows several field values to be stored in one slot, e.g. the 3 field values Johnny, B. and Good in the example above.

© C. Kemke CLIPS 1 9 Slot Restrictions Defined Template with Slot-Restrictions (Constraint-Attributes): (deftemplate person (slot name (type STRING)) (slot age (type INTEGER)) (slot gender (allowed-symbols male female)) )

© C. Kemke CLIPS 1 10 Slot Constraint-Attributes ::= | | ::= (type ) ::= + | ?VARIABLE ::= SYMBOL | STRING | LEXEME | INTEGER | FLOAT | NUMBER | INSTANCE-NAME | INSTANCE-ADDRESS | INSTANCE | FACT-ADDRESS | EXTERNAL-ADDRESS

© C. Kemke CLIPS 1 11 Slot Constraint-Attributes Type + Allowed Values (Enumeration, Collection) ::= (allowedsymbols ) | (allowedstrings ) | (allowed-lexemes ) | (allowedintegers ) | (allowedfloats ) | (allowednumbers ) | (allowed-instance-names ) | (allowedvalues )

© C. Kemke CLIPS 1 12 Slot Constraint-Attributes Range of Values (min and max value) ::= (range ) ::= | ?VARIABLE Number of Fillers (min and max) ::= (cardinality ) ::= | ?VARIABLE

© C. Kemke CLIPS 1 13 Variables and Wildcards single-field variablebinds single value ? e.g.?age, ?x, ?address ?fact-variable multi-field variable accepts multiple values; $? can bind multi-field value single-field wildcardmatches any single-field value ? multi-field wildcardmatches any multi-field value $?

© C. Kemke CLIPS 1 14 All Kinds of Variables (defrule birthday “A person’s birthday” ?f1 <- (person (name $?name) (age ?age)) ?f2 <- (has-birthday $?name) => (printout t “Happy Birthday,” $?name) (retract ?f1) (retract ?f2) (assert (person (name $?name) (age (+ ?age 1))))) Q: With which patterns does the Condition match? A: e.g. (person (name Johnny B. Good) (age 42))

© C. Kemke CLIPS 1 15 All Kinds of Variables 2 (defrule birthday “A person’s birthday” ?f1 <- (person (name ?name $?) (age ?age)) ?f2 <- (has-birthday ?name) => (printout t “Happy Birthday,” ?name) (retract ?f2) (modify ?f1 (age (+ ?age 1)))) Q1: What is $? matching with? Q2: What is the rule doing?

© C. Kemke CLIPS 1 16 Complex Condition Elements  logical connectives and, or, not to combine patterns  forall and exists – consider all matches/ only one match in further evaluation  logical – connects condition element and asserted fact in action (Truth Maintenance)  use test-condition (test )  field-constraints &, |, and &: attached to slot of (deftemplate) condition pattern

© C. Kemke CLIPS 1 17 Field Constraints (Connected Pattern Constraints) not ~ not this value (name ~Simpson) (age ~40) or | could be one of these values (name Simpson|Oswald) (age 30|40|50) and &attaches constraint to variable (name ?name&~Simpson) (name ?name&Harvey) expr. : adds expression as constraint (age ?age&:(> ?age 20)) (name ?name&:(eq (sub-string 1 1 ?name) "S") checks whether the sub- string from 1 to 1 (first letter) of the name is "S" checks whether the age is above 20

© C. Kemke CLIPS 1 18 Field Constraint (defrule you-wish “something with people and age” (person (name ?name) (age ?age&:(> ?age 20)) => (printout t ?name “is over twenty.” crlf) (printout t ?name “is “ ?age “years old.” crlf)) Q1: Which patterns match this Condition? Q2: What is the rule doing?

© C. Kemke CLIPS 1 19 Condition Patterns with Logical Connectives Complex Conditions with logical connectives: (or (pattern1) (pattern2)) Rule becomes active if one of the patterns matches. example: (or (birthday) (anniversary)) matches fact base with facts (birthday) or (anniversary) Equivalent for: and(is default) not existsto be fulfilled for one matching fact forallto be fulfilled for all facts which match based on first fact and variable binding

© C. Kemke CLIPS 1 20 Complex Condition Elements - or (defrule report-emergency (or (emergency (emergency-type fire) (location ?building)) (emergency (emergency-type bomb) (location ?building)) ) => (printout t “evacuate “ ?building) ) reports a building if there is a fire or bomb emergency in this building

© C. Kemke CLIPS 1 21 Complex Condition Elements – exists (defrule emergency-report (exists (or (emergency (emergency-type fire)) (emergency (emergency-type bomb))) ) => (printout t “There is an emergency.“ crlf ) ) prints one emergency-message if there is a fire or bomb emergency. (no further matching, firing, or printout)

© C. Kemke CLIPS 1 22 Complex Condition Elements – forall (defrule evacuated-all-buildings (forall (emergency (emergency-type fire | bomb) (location ?building) ) (evacuated (building ?building))) => (printout t “All buildings with emergency are evacuated “ crlf)) prints evacuated-message if for all buildings, which have a fire or bomb emergency, the building is evacuated.

© C. Kemke CLIPS 1 23 Exercise (defrule special-age “18, 21, 100” (or (person (name ?name) (age 18)) (person (name ?name) (age 21)) (person (name ?name) (age 100))) => (printout t ?name “ has a special age.”)) Task: Modify the condition pattern so that you use a variable for age, and field constraints for the values, and printout the name and age of any matching person.

© C. Kemke CLIPS 1 24 (deftemplate person (slot age (type INTEGER)) (multislot name (type STRING)) (slot gender (allowed-values f m)) ) (deffacts people (person (age 20) (name "Mike" "M." "Moore") (gender m)) (person (age 40) (name "James" "J." "James" ) (gender m)) (person (age 42) (name "Susan" "D." "More") (gender f)) (person (age 28) (name "John" "J." "Jones") (gender m)) ) (defrule what-am-I-doing (or (person (name ?first ?middle ?last&:(eq ?last "Moore"))) (person (name ?first ?middle ?last&:(eq ?last "More"))) ) => (printout t "Found " ?first " " ?last crlf) ) Q2: Can you simplify the Condition Element? Do it! Q1: What is the rule doing?

© C. Kemke CLIPS 1 25 bind-function bind-function – explicitly binds value to variable (bind ?age (read)) stores value of single field which is read into single-field variable ?age (bind ?name (readline)) stores line which is read as STRING into single-field STRING-variable ?address (bind ?address (explode$ (readline))) explode$ splits line which is read as STRING into multifield-value which is stored in multislot-variable ?address

© C. Kemke CLIPS 1 26 Open, Close File Open file for read/write: (open “ ” “r”)  is physical file-name (path)  is name used in program  “r” indicates read-access (“w”, “r+”) example: (open “example.dat” my-file “r”) (read my-file) Close file: (close )

© C. Kemke CLIPS 1 27 Input – read, readline read – input of single field readline – input of complete (line as string) general: (read ) refers to file-name in program (read) keyboard is default read with bind-function to bind input to variable: (bind ?input (read)) (bind $?input (readline))

© C. Kemke CLIPS 1 28 Input – read, readline (read / readline )  default is keyboard/terminal  file has to be opened using (open “ ” “r”)  is physical file-name (can include path)  is name used in read command  “r” indicates read-access example: (open “example.dat” example “r”) (read example) use with bind-function to bind input to variable

© C. Kemke CLIPS 1 29 Output - printout (printout... ) u t terminal is standard u otherwise refers to a file-name file has to be opened using (open “ ” “w” )  is physical file-name (can include path)  is name used in printout command v “w” indicates write-access example: (open “example.dat” my-output “w” ) (printout my-output ?name crlf)

© C. Kemke CLIPS 1 30 Rules - Runtime Effects refraction  each rule fires only once on the same data agenda  rules are activated in sequence and put on agenda; agenda is like a stack: the last rule fires first salience  sequence of rule firings - in case of a conflicts – is determined by their set salience factor: the higher the salience, the higher the rule priority

© C. Kemke CLIPS 1 31 Rules - Salience (defrule say-hello (declare (salience 10)) (person (name ?name)) => (printout t “Hello,” ?name)) (defrule say-happy-birthday (declare (salience 100)) (person (name ?name)) => (printout t “Happy Birthday,” ?name)) Rules defined with salience factor: The higher the salience, the higher the rule priority in conflict situations.