1. Computer Based Tutoring
Simulating a human tutor
For algebra word problems

2. Steps in Solving Word Problem
Read problem statement
Identify values of variables
Construct equation for problem with values substituted for variables
Operate on equation to isolate unknown variable
Return solution

3. Tutor Dialog Present problem statement
Prompt student for values of variables
Display problem statement with values substituted for variables
Enable student to choose from list of equations
Enable student to operate on equation to isolate unknown variable
Return solution

4. CLIPS implementation
Facts store problem data along with performance and sequencing information
Rules
Prompt student for information
Enable student to answer questions
Provide feedback to student as to whether student response is correct

5. Tutor Fact Templates
Defines problem template which specifies problem type (distance, number, .. Etc) and a problem statement
(deftemplate problem-data
(slot ptype)
(slot statement) )
Defines equation template which specifies problem type, variable and coefficients
(deftemplate eqtn
(slot coef)
(slot var)
(slot lcon)
(slot rcon)

6. Tutor Facts Defines template with multslot for numbered equations
(deftemplate neqt
(multislot nmbr-eqt) )
Stores equations as numbered strings in a multislot for student selection
(deffacts eqts
(nmbr-eqtn "1 c*v+lft = rght" "2 s*t = d" "end") )
Behind the scene storage of actual equations
(deffacts eqtn-list
(eqtn (ptype number) (coef 2) (var n) (lcon 13) (rcon 75))
(eqtn (ptype distance) (coef 3) (var t) (lcon 0) (rcon 180)) )

7. Rule for presenting and selecting problem type
(defrule show-types
=>
(printout t "Input problem type : number, age, distance" crlf)
(assert (cur-typ (read)))
(assert (cur-state dialog0)) )
Rule will fire first because antecedent has no patterns to match.
Prints prompt for problem types and asserts two facts:
Cur-typ contains type user enters
Cur-state has value dialog0

8. Rule to state problem (defrule show-prob
?idx <- (cur-state dialog0)
(cur-typ ?t)
(problem-data
(ptype ?t)
(statement ?s) )
=>
(printout t ?s crlf)
(retract ?idx)
(assert (cur-state dialog1)) )

9. Tutor Facts Template for making a list of equations (deftemplate neqt
(multislot nmbr-eqt) )
Fact list of numbered equations
(deffacts eqts
(nmbr-eqtn "1 c*v+lft = rght" "2 s*t = d" "end") )
User selects from this list

10. Tutor Facts List of problem statements.
CLIPS selects statement based on problem type.
(deffacts problems
(problem-data
(ptype number)
(statement "The sum of twice a number plus 13 is 75 Find the number ") )
(ptype distance)
(statement "A car travels 180 miles in 3 hours. Find the speed.")

11. Rule to Show Problem (defrule show-prob ?idx <- (cur-state dialog0)
(cur-typ ?t)
(problem-data
(ptype ?t)
(statement ?s) )
=>
(printout t ?s crlf)
(printout t " " crlf)
(retract ?idx)
(assert (cur-state dialog1)) )
Rule select fact problem-data on cur-typ = ptype